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### view gcc/gimple-ssa-strength-reduction.c @ 16:04ced10e8804

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author | kono |
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date | Fri, 27 Oct 2017 22:46:09 +0900 |

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/* Straight-line strength reduction. Copyright (C) 2012-2017 Free Software Foundation, Inc. Contributed by Bill Schmidt, IBM <wschmidt@linux.ibm.com> This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GCC; see the file COPYING3. If not see <http://www.gnu.org/licenses/>. */ /* There are many algorithms for performing strength reduction on loops. This is not one of them. IVOPTS handles strength reduction of induction variables just fine. This pass is intended to pick up the crumbs it leaves behind, by considering opportunities for strength reduction along dominator paths. Strength reduction addresses explicit multiplies, and certain multiplies implicit in addressing expressions. It would also be possible to apply strength reduction to divisions and modulos, but such opportunities are relatively uncommon. Strength reduction is also currently restricted to integer operations. If desired, it could be extended to floating-point operations under control of something like -funsafe-math-optimizations. */ #include "config.h" #include "system.h" #include "coretypes.h" #include "backend.h" #include "rtl.h" #include "tree.h" #include "gimple.h" #include "cfghooks.h" #include "tree-pass.h" #include "ssa.h" #include "expmed.h" #include "gimple-pretty-print.h" #include "fold-const.h" #include "gimple-iterator.h" #include "gimplify-me.h" #include "stor-layout.h" #include "cfgloop.h" #include "tree-cfg.h" #include "domwalk.h" #include "params.h" #include "tree-ssa-address.h" #include "tree-affine.h" #include "builtins.h" /* Information about a strength reduction candidate. Each statement in the candidate table represents an expression of one of the following forms (the special case of CAND_REF will be described later): (CAND_MULT) S1: X = (B + i) * S (CAND_ADD) S1: X = B + (i * S) Here X and B are SSA names, i is an integer constant, and S is either an SSA name or a constant. We call B the "base," i the "index", and S the "stride." Any statement S0 that dominates S1 and is of the form: (CAND_MULT) S0: Y = (B + i') * S (CAND_ADD) S0: Y = B + (i' * S) is called a "basis" for S1. In both cases, S1 may be replaced by S1': X = Y + (i - i') * S, where (i - i') * S is folded to the extent possible. All gimple statements are visited in dominator order, and each statement that may contribute to one of the forms of S1 above is given at least one entry in the candidate table. Such statements include addition, pointer addition, subtraction, multiplication, negation, copies, and nontrivial type casts. If a statement may represent more than one expression of the forms of S1 above, multiple "interpretations" are stored in the table and chained together. Examples: * An add of two SSA names may treat either operand as the base. * A multiply of two SSA names, likewise. * A copy or cast may be thought of as either a CAND_MULT with i = 0 and S = 1, or as a CAND_ADD with i = 0 or S = 0. Candidate records are allocated from an obstack. They are addressed both from a hash table keyed on S1, and from a vector of candidate pointers arranged in predominator order. Opportunity note ---------------- Currently we don't recognize: S0: Y = (S * i') - B S1: X = (S * i) - B as a strength reduction opportunity, even though this S1 would also be replaceable by the S1' above. This can be added if it comes up in practice. Strength reduction in addressing -------------------------------- There is another kind of candidate known as CAND_REF. A CAND_REF describes a statement containing a memory reference having complex addressing that might benefit from strength reduction. Specifically, we are interested in references for which get_inner_reference returns a base address, offset, and bitpos as follows: base: MEM_REF (T1, C1) offset: MULT_EXPR (PLUS_EXPR (T2, C2), C3) bitpos: C4 * BITS_PER_UNIT Here T1 and T2 are arbitrary trees, and C1, C2, C3, C4 are arbitrary integer constants. Note that C2 may be zero, in which case the offset will be MULT_EXPR (T2, C3). When this pattern is recognized, the original memory reference can be replaced with: MEM_REF (POINTER_PLUS_EXPR (T1, MULT_EXPR (T2, C3)), C1 + (C2 * C3) + C4) which distributes the multiply to allow constant folding. When two or more addressing expressions can be represented by MEM_REFs of this form, differing only in the constants C1, C2, and C4, making this substitution produces more efficient addressing during the RTL phases. When there are not at least two expressions with the same values of T1, T2, and C3, there is nothing to be gained by the replacement. Strength reduction of CAND_REFs uses the same infrastructure as that used by CAND_MULTs and CAND_ADDs. We record T1 in the base (B) field, MULT_EXPR (T2, C3) in the stride (S) field, and C1 + (C2 * C3) + C4 in the index (i) field. A basis for a CAND_REF is thus another CAND_REF with the same B and S values. When at least two CAND_REFs are chained together using the basis relation, each of them is replaced as above, resulting in improved code generation for addressing. Conditional candidates ====================== Conditional candidates are best illustrated with an example. Consider the code sequence: (1) x_0 = ...; (2) a_0 = x_0 * 5; MULT (B: x_0; i: 0; S: 5) if (...) (3) x_1 = x_0 + 1; ADD (B: x_0, i: 1; S: 1) (4) x_2 = PHI <x_0, x_1>; PHI (B: x_0, i: 0, S: 1) (5) x_3 = x_2 + 1; ADD (B: x_2, i: 1, S: 1) (6) a_1 = x_3 * 5; MULT (B: x_2, i: 1; S: 5) Here strength reduction is complicated by the uncertain value of x_2. A legitimate transformation is: (1) x_0 = ...; (2) a_0 = x_0 * 5; if (...) { (3) [x_1 = x_0 + 1;] (3a) t_1 = a_0 + 5; } (4) [x_2 = PHI <x_0, x_1>;] (4a) t_2 = PHI <a_0, t_1>; (5) [x_3 = x_2 + 1;] (6r) a_1 = t_2 + 5; where the bracketed instructions may go dead. To recognize this opportunity, we have to observe that statement (6) has a "hidden basis" (2). The hidden basis is unlike a normal basis in that the statement and the hidden basis have different base SSA names (x_2 and x_0, respectively). The relationship is established when a statement's base name (x_2) is defined by a phi statement (4), each argument of which (x_0, x_1) has an identical "derived base name." If the argument is defined by a candidate (as x_1 is by (3)) that is a CAND_ADD having a stride of 1, the derived base name of the argument is the base name of the candidate (x_0). Otherwise, the argument itself is its derived base name (as is the case with argument x_0). The hidden basis for statement (6) is the nearest dominating candidate whose base name is the derived base name (x_0) of the feeding phi (4), and whose stride is identical to that of the statement. We can then create the new "phi basis" (4a) and feeding adds along incoming arcs (3a), allowing the final replacement of (6) by the strength-reduced (6r). To facilitate this, a new kind of candidate (CAND_PHI) is introduced. A CAND_PHI is not a candidate for replacement, but is maintained in the candidate table to ease discovery of hidden bases. Any phi statement whose arguments share a common derived base name is entered into the table with the derived base name, an (arbitrary) index of zero, and a stride of 1. A statement with a hidden basis can then be detected by simply looking up its feeding phi definition in the candidate table, extracting the derived base name, and searching for a basis in the usual manner after substituting the derived base name. Note that the transformation is only valid when the original phi and the statements that define the phi's arguments are all at the same position in the loop hierarchy. */ /* Index into the candidate vector, offset by 1. VECs are zero-based, while cand_idx's are one-based, with zero indicating null. */ typedef unsigned cand_idx; /* The kind of candidate. */ enum cand_kind { CAND_MULT, CAND_ADD, CAND_REF, CAND_PHI }; struct slsr_cand_d { /* The candidate statement S1. */ gimple *cand_stmt; /* The base expression B: often an SSA name, but not always. */ tree base_expr; /* The stride S. */ tree stride; /* The index constant i. */ widest_int index; /* The type of the candidate. This is normally the type of base_expr, but casts may have occurred when combining feeding instructions. A candidate can only be a basis for candidates of the same final type. (For CAND_REFs, this is the type to be used for operand 1 of the replacement MEM_REF.) */ tree cand_type; /* The type to be used to interpret the stride field when the stride is not a constant. Normally the same as the type of the recorded stride, but when the stride has been cast we need to maintain that knowledge in order to make legal substitutions without losing precision. When the stride is a constant, this will be sizetype. */ tree stride_type; /* The kind of candidate (CAND_MULT, etc.). */ enum cand_kind kind; /* Index of this candidate in the candidate vector. */ cand_idx cand_num; /* Index of the next candidate record for the same statement. A statement may be useful in more than one way (e.g., due to commutativity). So we can have multiple "interpretations" of a statement. */ cand_idx next_interp; /* Index of the basis statement S0, if any, in the candidate vector. */ cand_idx basis; /* First candidate for which this candidate is a basis, if one exists. */ cand_idx dependent; /* Next candidate having the same basis as this one. */ cand_idx sibling; /* If this is a conditional candidate, the CAND_PHI candidate that defines the base SSA name B. */ cand_idx def_phi; /* Savings that can be expected from eliminating dead code if this candidate is replaced. */ int dead_savings; /* For PHI candidates, use a visited flag to keep from processing the same PHI twice from multiple paths. */ int visited; /* We sometimes have to cache a phi basis with a phi candidate to avoid processing it twice. Valid only if visited==1. */ tree cached_basis; }; typedef struct slsr_cand_d slsr_cand, *slsr_cand_t; typedef const struct slsr_cand_d *const_slsr_cand_t; /* Pointers to candidates are chained together as part of a mapping from base expressions to the candidates that use them. */ struct cand_chain_d { /* Base expression for the chain of candidates: often, but not always, an SSA name. */ tree base_expr; /* Pointer to a candidate. */ slsr_cand_t cand; /* Chain pointer. */ struct cand_chain_d *next; }; typedef struct cand_chain_d cand_chain, *cand_chain_t; typedef const struct cand_chain_d *const_cand_chain_t; /* Information about a unique "increment" associated with candidates having an SSA name for a stride. An increment is the difference between the index of the candidate and the index of its basis, i.e., (i - i') as discussed in the module commentary. When we are not going to generate address arithmetic we treat increments that differ only in sign as the same, allowing sharing of the cost of initializers. The absolute value of the increment is stored in the incr_info. */ struct incr_info_d { /* The increment that relates a candidate to its basis. */ widest_int incr; /* How many times the increment occurs in the candidate tree. */ unsigned count; /* Cost of replacing candidates using this increment. Negative and zero costs indicate replacement should be performed. */ int cost; /* If this increment is profitable but is not -1, 0, or 1, it requires an initializer T_0 = stride * incr to be found or introduced in the nearest common dominator of all candidates. This field holds T_0 for subsequent use. */ tree initializer; /* If the initializer was found to already exist, this is the block where it was found. */ basic_block init_bb; }; typedef struct incr_info_d incr_info, *incr_info_t; /* Candidates are maintained in a vector. If candidate X dominates candidate Y, then X appears before Y in the vector; but the converse does not necessarily hold. */ static vec<slsr_cand_t> cand_vec; enum cost_consts { COST_NEUTRAL = 0, COST_INFINITE = 1000 }; enum stride_status { UNKNOWN_STRIDE = 0, KNOWN_STRIDE = 1 }; enum phi_adjust_status { NOT_PHI_ADJUST = 0, PHI_ADJUST = 1 }; enum count_phis_status { DONT_COUNT_PHIS = 0, COUNT_PHIS = 1 }; /* Constrain how many PHI nodes we will visit for a conditional candidate (depth and breadth). */ const int MAX_SPREAD = 16; /* Pointer map embodying a mapping from statements to candidates. */ static hash_map<gimple *, slsr_cand_t> *stmt_cand_map; /* Obstack for candidates. */ static struct obstack cand_obstack; /* Obstack for candidate chains. */ static struct obstack chain_obstack; /* An array INCR_VEC of incr_infos is used during analysis of related candidates having an SSA name for a stride. INCR_VEC_LEN describes its current length. MAX_INCR_VEC_LEN is used to avoid costly pathological cases. */ static incr_info_t incr_vec; static unsigned incr_vec_len; const int MAX_INCR_VEC_LEN = 16; /* For a chain of candidates with unknown stride, indicates whether or not we must generate pointer arithmetic when replacing statements. */ static bool address_arithmetic_p; /* Forward function declarations. */ static slsr_cand_t base_cand_from_table (tree); static tree introduce_cast_before_cand (slsr_cand_t, tree, tree); static bool legal_cast_p_1 (tree, tree); /* Produce a pointer to the IDX'th candidate in the candidate vector. */ static slsr_cand_t lookup_cand (cand_idx idx) { return cand_vec[idx - 1]; } /* Helper for hashing a candidate chain header. */ struct cand_chain_hasher : nofree_ptr_hash <cand_chain> { static inline hashval_t hash (const cand_chain *); static inline bool equal (const cand_chain *, const cand_chain *); }; inline hashval_t cand_chain_hasher::hash (const cand_chain *p) { tree base_expr = p->base_expr; return iterative_hash_expr (base_expr, 0); } inline bool cand_chain_hasher::equal (const cand_chain *chain1, const cand_chain *chain2) { return operand_equal_p (chain1->base_expr, chain2->base_expr, 0); } /* Hash table embodying a mapping from base exprs to chains of candidates. */ static hash_table<cand_chain_hasher> *base_cand_map; /* Pointer map used by tree_to_aff_combination_expand. */ static hash_map<tree, name_expansion *> *name_expansions; /* Pointer map embodying a mapping from bases to alternative bases. */ static hash_map<tree, tree> *alt_base_map; /* Given BASE, use the tree affine combiniation facilities to find the underlying tree expression for BASE, with any immediate offset excluded. N.B. we should eliminate this backtracking with better forward analysis in a future release. */ static tree get_alternative_base (tree base) { tree *result = alt_base_map->get (base); if (result == NULL) { tree expr; aff_tree aff; tree_to_aff_combination_expand (base, TREE_TYPE (base), &aff, &name_expansions); aff.offset = 0; expr = aff_combination_to_tree (&aff); gcc_assert (!alt_base_map->put (base, base == expr ? NULL : expr)); return expr == base ? NULL : expr; } return *result; } /* Look in the candidate table for a CAND_PHI that defines BASE and return it if found; otherwise return NULL. */ static cand_idx find_phi_def (tree base) { slsr_cand_t c; if (TREE_CODE (base) != SSA_NAME) return 0; c = base_cand_from_table (base); if (!c || c->kind != CAND_PHI || SSA_NAME_OCCURS_IN_ABNORMAL_PHI (gimple_phi_result (c->cand_stmt))) return 0; return c->cand_num; } /* Determine whether all uses of NAME are directly or indirectly used by STMT. That is, we want to know whether if STMT goes dead, the definition of NAME also goes dead. */ static bool uses_consumed_by_stmt (tree name, gimple *stmt, unsigned recurse = 0) { gimple *use_stmt; imm_use_iterator iter; bool retval = true; FOR_EACH_IMM_USE_STMT (use_stmt, iter, name) { if (use_stmt == stmt || is_gimple_debug (use_stmt)) continue; if (!is_gimple_assign (use_stmt) || !gimple_get_lhs (use_stmt) || !is_gimple_reg (gimple_get_lhs (use_stmt)) || recurse >= 10 || !uses_consumed_by_stmt (gimple_get_lhs (use_stmt), stmt, recurse + 1)) { retval = false; BREAK_FROM_IMM_USE_STMT (iter); } } return retval; } /* Helper routine for find_basis_for_candidate. May be called twice: once for the candidate's base expr, and optionally again either for the candidate's phi definition or for a CAND_REF's alternative base expression. */ static slsr_cand_t find_basis_for_base_expr (slsr_cand_t c, tree base_expr) { cand_chain mapping_key; cand_chain_t chain; slsr_cand_t basis = NULL; // Limit potential of N^2 behavior for long candidate chains. int iters = 0; int max_iters = PARAM_VALUE (PARAM_MAX_SLSR_CANDIDATE_SCAN); mapping_key.base_expr = base_expr; chain = base_cand_map->find (&mapping_key); for (; chain && iters < max_iters; chain = chain->next, ++iters) { slsr_cand_t one_basis = chain->cand; if (one_basis->kind != c->kind || one_basis->cand_stmt == c->cand_stmt || !operand_equal_p (one_basis->stride, c->stride, 0) || !types_compatible_p (one_basis->cand_type, c->cand_type) || !types_compatible_p (one_basis->stride_type, c->stride_type) || !dominated_by_p (CDI_DOMINATORS, gimple_bb (c->cand_stmt), gimple_bb (one_basis->cand_stmt))) continue; tree lhs = gimple_assign_lhs (one_basis->cand_stmt); if (lhs && TREE_CODE (lhs) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs)) continue; if (!basis || basis->cand_num < one_basis->cand_num) basis = one_basis; } return basis; } /* Use the base expr from candidate C to look for possible candidates that can serve as a basis for C. Each potential basis must also appear in a block that dominates the candidate statement and have the same stride and type. If more than one possible basis exists, the one with highest index in the vector is chosen; this will be the most immediately dominating basis. */ static int find_basis_for_candidate (slsr_cand_t c) { slsr_cand_t basis = find_basis_for_base_expr (c, c->base_expr); /* If a candidate doesn't have a basis using its base expression, it may have a basis hidden by one or more intervening phis. */ if (!basis && c->def_phi) { basic_block basis_bb, phi_bb; slsr_cand_t phi_cand = lookup_cand (c->def_phi); basis = find_basis_for_base_expr (c, phi_cand->base_expr); if (basis) { /* A hidden basis must dominate the phi-definition of the candidate's base name. */ phi_bb = gimple_bb (phi_cand->cand_stmt); basis_bb = gimple_bb (basis->cand_stmt); if (phi_bb == basis_bb || !dominated_by_p (CDI_DOMINATORS, phi_bb, basis_bb)) { basis = NULL; c->basis = 0; } /* If we found a hidden basis, estimate additional dead-code savings if the phi and its feeding statements can be removed. */ tree feeding_var = gimple_phi_result (phi_cand->cand_stmt); if (basis && uses_consumed_by_stmt (feeding_var, c->cand_stmt)) c->dead_savings += phi_cand->dead_savings; } } if (flag_expensive_optimizations && !basis && c->kind == CAND_REF) { tree alt_base_expr = get_alternative_base (c->base_expr); if (alt_base_expr) basis = find_basis_for_base_expr (c, alt_base_expr); } if (basis) { c->sibling = basis->dependent; basis->dependent = c->cand_num; return basis->cand_num; } return 0; } /* Record a mapping from BASE to C, indicating that C may potentially serve as a basis using that base expression. BASE may be the same as C->BASE_EXPR; alternatively BASE can be a different tree that share the underlining expression of C->BASE_EXPR. */ static void record_potential_basis (slsr_cand_t c, tree base) { cand_chain_t node; cand_chain **slot; gcc_assert (base); node = (cand_chain_t) obstack_alloc (&chain_obstack, sizeof (cand_chain)); node->base_expr = base; node->cand = c; node->next = NULL; slot = base_cand_map->find_slot (node, INSERT); if (*slot) { cand_chain_t head = (cand_chain_t) (*slot); node->next = head->next; head->next = node; } else *slot = node; } /* Allocate storage for a new candidate and initialize its fields. Attempt to find a basis for the candidate. For CAND_REF, an alternative base may also be recorded and used to find a basis. This helps cases where the expression hidden behind BASE (which is usually an SSA_NAME) has immediate offset, e.g. a2[i][j] = 1; a2[i + 20][j] = 2; */ static slsr_cand_t alloc_cand_and_find_basis (enum cand_kind kind, gimple *gs, tree base, const widest_int &index, tree stride, tree ctype, tree stype, unsigned savings) { slsr_cand_t c = (slsr_cand_t) obstack_alloc (&cand_obstack, sizeof (slsr_cand)); c->cand_stmt = gs; c->base_expr = base; c->stride = stride; c->index = index; c->cand_type = ctype; c->stride_type = stype; c->kind = kind; c->cand_num = cand_vec.length () + 1; c->next_interp = 0; c->dependent = 0; c->sibling = 0; c->def_phi = kind == CAND_MULT ? find_phi_def (base) : 0; c->dead_savings = savings; c->visited = 0; c->cached_basis = NULL_TREE; cand_vec.safe_push (c); if (kind == CAND_PHI) c->basis = 0; else c->basis = find_basis_for_candidate (c); record_potential_basis (c, base); if (flag_expensive_optimizations && kind == CAND_REF) { tree alt_base = get_alternative_base (base); if (alt_base) record_potential_basis (c, alt_base); } return c; } /* Determine the target cost of statement GS when compiling according to SPEED. */ static int stmt_cost (gimple *gs, bool speed) { tree lhs, rhs1, rhs2; machine_mode lhs_mode; gcc_assert (is_gimple_assign (gs)); lhs = gimple_assign_lhs (gs); rhs1 = gimple_assign_rhs1 (gs); lhs_mode = TYPE_MODE (TREE_TYPE (lhs)); switch (gimple_assign_rhs_code (gs)) { case MULT_EXPR: rhs2 = gimple_assign_rhs2 (gs); if (tree_fits_shwi_p (rhs2)) return mult_by_coeff_cost (tree_to_shwi (rhs2), lhs_mode, speed); gcc_assert (TREE_CODE (rhs1) != INTEGER_CST); return mul_cost (speed, lhs_mode); case PLUS_EXPR: case POINTER_PLUS_EXPR: case MINUS_EXPR: return add_cost (speed, lhs_mode); case NEGATE_EXPR: return neg_cost (speed, lhs_mode); CASE_CONVERT: return convert_cost (lhs_mode, TYPE_MODE (TREE_TYPE (rhs1)), speed); /* Note that we don't assign costs to copies that in most cases will go away. */ case SSA_NAME: return 0; default: ; } gcc_unreachable (); return 0; } /* Look up the defining statement for BASE_IN and return a pointer to its candidate in the candidate table, if any; otherwise NULL. Only CAND_ADD and CAND_MULT candidates are returned. */ static slsr_cand_t base_cand_from_table (tree base_in) { slsr_cand_t *result; gimple *def = SSA_NAME_DEF_STMT (base_in); if (!def) return (slsr_cand_t) NULL; result = stmt_cand_map->get (def); if (result && (*result)->kind != CAND_REF) return *result; return (slsr_cand_t) NULL; } /* Add an entry to the statement-to-candidate mapping. */ static void add_cand_for_stmt (gimple *gs, slsr_cand_t c) { gcc_assert (!stmt_cand_map->put (gs, c)); } /* Given PHI which contains a phi statement, determine whether it satisfies all the requirements of a phi candidate. If so, create a candidate. Note that a CAND_PHI never has a basis itself, but is used to help find a basis for subsequent candidates. */ static void slsr_process_phi (gphi *phi, bool speed) { unsigned i; tree arg0_base = NULL_TREE, base_type; slsr_cand_t c; struct loop *cand_loop = gimple_bb (phi)->loop_father; unsigned savings = 0; /* A CAND_PHI requires each of its arguments to have the same derived base name. (See the module header commentary for a definition of derived base names.) Furthermore, all feeding definitions must be in the same position in the loop hierarchy as PHI. */ for (i = 0; i < gimple_phi_num_args (phi); i++) { slsr_cand_t arg_cand; tree arg = gimple_phi_arg_def (phi, i); tree derived_base_name = NULL_TREE; gimple *arg_stmt = NULL; basic_block arg_bb = NULL; if (TREE_CODE (arg) != SSA_NAME) return; arg_cand = base_cand_from_table (arg); if (arg_cand) { while (arg_cand->kind != CAND_ADD && arg_cand->kind != CAND_PHI) { if (!arg_cand->next_interp) return; arg_cand = lookup_cand (arg_cand->next_interp); } if (!integer_onep (arg_cand->stride)) return; derived_base_name = arg_cand->base_expr; arg_stmt = arg_cand->cand_stmt; arg_bb = gimple_bb (arg_stmt); /* Gather potential dead code savings if the phi statement can be removed later on. */ if (uses_consumed_by_stmt (arg, phi)) { if (gimple_code (arg_stmt) == GIMPLE_PHI) savings += arg_cand->dead_savings; else savings += stmt_cost (arg_stmt, speed); } } else if (SSA_NAME_IS_DEFAULT_DEF (arg)) { derived_base_name = arg; arg_bb = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)); } if (!arg_bb || arg_bb->loop_father != cand_loop) return; if (i == 0) arg0_base = derived_base_name; else if (!operand_equal_p (derived_base_name, arg0_base, 0)) return; } /* Create the candidate. "alloc_cand_and_find_basis" is named misleadingly for this case, as no basis will be sought for a CAND_PHI. */ base_type = TREE_TYPE (arg0_base); c = alloc_cand_and_find_basis (CAND_PHI, phi, arg0_base, 0, integer_one_node, base_type, sizetype, savings); /* Add the candidate to the statement-candidate mapping. */ add_cand_for_stmt (phi, c); } /* Given PBASE which is a pointer to tree, look up the defining statement for it and check whether the candidate is in the form of: X = B + (1 * S), S is integer constant X = B + (i * S), S is integer one If so, set PBASE to the candidate's base_expr and return double int (i * S). Otherwise, just return double int zero. */ static widest_int backtrace_base_for_ref (tree *pbase) { tree base_in = *pbase; slsr_cand_t base_cand; STRIP_NOPS (base_in); /* Strip off widening conversion(s) to handle cases where e.g. 'B' is widened from an 'int' in order to calculate a 64-bit address. */ if (CONVERT_EXPR_P (base_in) && legal_cast_p_1 (TREE_TYPE (base_in), TREE_TYPE (TREE_OPERAND (base_in, 0)))) base_in = get_unwidened (base_in, NULL_TREE); if (TREE_CODE (base_in) != SSA_NAME) return 0; base_cand = base_cand_from_table (base_in); while (base_cand && base_cand->kind != CAND_PHI) { if (base_cand->kind == CAND_ADD && base_cand->index == 1 && TREE_CODE (base_cand->stride) == INTEGER_CST) { /* X = B + (1 * S), S is integer constant. */ *pbase = base_cand->base_expr; return wi::to_widest (base_cand->stride); } else if (base_cand->kind == CAND_ADD && TREE_CODE (base_cand->stride) == INTEGER_CST && integer_onep (base_cand->stride)) { /* X = B + (i * S), S is integer one. */ *pbase = base_cand->base_expr; return base_cand->index; } if (base_cand->next_interp) base_cand = lookup_cand (base_cand->next_interp); else base_cand = NULL; } return 0; } /* Look for the following pattern: *PBASE: MEM_REF (T1, C1) *POFFSET: MULT_EXPR (T2, C3) [C2 is zero] or MULT_EXPR (PLUS_EXPR (T2, C2), C3) or MULT_EXPR (MINUS_EXPR (T2, -C2), C3) *PINDEX: C4 * BITS_PER_UNIT If not present, leave the input values unchanged and return FALSE. Otherwise, modify the input values as follows and return TRUE: *PBASE: T1 *POFFSET: MULT_EXPR (T2, C3) *PINDEX: C1 + (C2 * C3) + C4 When T2 is recorded by a CAND_ADD in the form of (T2' + C5), it will be further restructured to: *PBASE: T1 *POFFSET: MULT_EXPR (T2', C3) *PINDEX: C1 + (C2 * C3) + C4 + (C5 * C3) */ static bool restructure_reference (tree *pbase, tree *poffset, widest_int *pindex, tree *ptype) { tree base = *pbase, offset = *poffset; widest_int index = *pindex; tree mult_op0, t1, t2, type; widest_int c1, c2, c3, c4, c5; if (!base || !offset || TREE_CODE (base) != MEM_REF || TREE_CODE (offset) != MULT_EXPR || TREE_CODE (TREE_OPERAND (offset, 1)) != INTEGER_CST || wi::umod_floor (index, BITS_PER_UNIT) != 0) return false; t1 = TREE_OPERAND (base, 0); c1 = widest_int::from (mem_ref_offset (base), SIGNED); type = TREE_TYPE (TREE_OPERAND (base, 1)); mult_op0 = TREE_OPERAND (offset, 0); c3 = wi::to_widest (TREE_OPERAND (offset, 1)); if (TREE_CODE (mult_op0) == PLUS_EXPR) if (TREE_CODE (TREE_OPERAND (mult_op0, 1)) == INTEGER_CST) { t2 = TREE_OPERAND (mult_op0, 0); c2 = wi::to_widest (TREE_OPERAND (mult_op0, 1)); } else return false; else if (TREE_CODE (mult_op0) == MINUS_EXPR) if (TREE_CODE (TREE_OPERAND (mult_op0, 1)) == INTEGER_CST) { t2 = TREE_OPERAND (mult_op0, 0); c2 = -wi::to_widest (TREE_OPERAND (mult_op0, 1)); } else return false; else { t2 = mult_op0; c2 = 0; } c4 = index >> LOG2_BITS_PER_UNIT; c5 = backtrace_base_for_ref (&t2); *pbase = t1; *poffset = fold_build2 (MULT_EXPR, sizetype, fold_convert (sizetype, t2), wide_int_to_tree (sizetype, c3)); *pindex = c1 + c2 * c3 + c4 + c5 * c3; *ptype = type; return true; } /* Given GS which contains a data reference, create a CAND_REF entry in the candidate table and attempt to find a basis. */ static void slsr_process_ref (gimple *gs) { tree ref_expr, base, offset, type; HOST_WIDE_INT bitsize, bitpos; machine_mode mode; int unsignedp, reversep, volatilep; slsr_cand_t c; if (gimple_vdef (gs)) ref_expr = gimple_assign_lhs (gs); else ref_expr = gimple_assign_rhs1 (gs); if (!handled_component_p (ref_expr) || TREE_CODE (ref_expr) == BIT_FIELD_REF || (TREE_CODE (ref_expr) == COMPONENT_REF && DECL_BIT_FIELD (TREE_OPERAND (ref_expr, 1)))) return; base = get_inner_reference (ref_expr, &bitsize, &bitpos, &offset, &mode, &unsignedp, &reversep, &volatilep); if (reversep) return; widest_int index = bitpos; if (!restructure_reference (&base, &offset, &index, &type)) return; c = alloc_cand_and_find_basis (CAND_REF, gs, base, index, offset, type, sizetype, 0); /* Add the candidate to the statement-candidate mapping. */ add_cand_for_stmt (gs, c); } /* Create a candidate entry for a statement GS, where GS multiplies two SSA names BASE_IN and STRIDE_IN. Propagate any known information about the two SSA names into the new candidate. Return the new candidate. */ static slsr_cand_t create_mul_ssa_cand (gimple *gs, tree base_in, tree stride_in, bool speed) { tree base = NULL_TREE, stride = NULL_TREE, ctype = NULL_TREE; tree stype = NULL_TREE; widest_int index; unsigned savings = 0; slsr_cand_t c; slsr_cand_t base_cand = base_cand_from_table (base_in); /* Look at all interpretations of the base candidate, if necessary, to find information to propagate into this candidate. */ while (base_cand && !base && base_cand->kind != CAND_PHI) { if (base_cand->kind == CAND_MULT && integer_onep (base_cand->stride)) { /* Y = (B + i') * 1 X = Y * Z ================ X = (B + i') * Z */ base = base_cand->base_expr; index = base_cand->index; stride = stride_in; ctype = base_cand->cand_type; stype = TREE_TYPE (stride_in); if (has_single_use (base_in)) savings = (base_cand->dead_savings + stmt_cost (base_cand->cand_stmt, speed)); } else if (base_cand->kind == CAND_ADD && TREE_CODE (base_cand->stride) == INTEGER_CST) { /* Y = B + (i' * S), S constant X = Y * Z ============================ X = B + ((i' * S) * Z) */ base = base_cand->base_expr; index = base_cand->index * wi::to_widest (base_cand->stride); stride = stride_in; ctype = base_cand->cand_type; stype = TREE_TYPE (stride_in); if (has_single_use (base_in)) savings = (base_cand->dead_savings + stmt_cost (base_cand->cand_stmt, speed)); } if (base_cand->next_interp) base_cand = lookup_cand (base_cand->next_interp); else base_cand = NULL; } if (!base) { /* No interpretations had anything useful to propagate, so produce X = (Y + 0) * Z. */ base = base_in; index = 0; stride = stride_in; ctype = TREE_TYPE (base_in); stype = TREE_TYPE (stride_in); } c = alloc_cand_and_find_basis (CAND_MULT, gs, base, index, stride, ctype, stype, savings); return c; } /* Create a candidate entry for a statement GS, where GS multiplies SSA name BASE_IN by constant STRIDE_IN. Propagate any known information about BASE_IN into the new candidate. Return the new candidate. */ static slsr_cand_t create_mul_imm_cand (gimple *gs, tree base_in, tree stride_in, bool speed) { tree base = NULL_TREE, stride = NULL_TREE, ctype = NULL_TREE; widest_int index, temp; unsigned savings = 0; slsr_cand_t c; slsr_cand_t base_cand = base_cand_from_table (base_in); /* Look at all interpretations of the base candidate, if necessary, to find information to propagate into this candidate. */ while (base_cand && !base && base_cand->kind != CAND_PHI) { if (base_cand->kind == CAND_MULT && TREE_CODE (base_cand->stride) == INTEGER_CST) { /* Y = (B + i') * S, S constant X = Y * c ============================ X = (B + i') * (S * c) */ temp = wi::to_widest (base_cand->stride) * wi::to_widest (stride_in); if (wi::fits_to_tree_p (temp, TREE_TYPE (stride_in))) { base = base_cand->base_expr; index = base_cand->index; stride = wide_int_to_tree (TREE_TYPE (stride_in), temp); ctype = base_cand->cand_type; if (has_single_use (base_in)) savings = (base_cand->dead_savings + stmt_cost (base_cand->cand_stmt, speed)); } } else if (base_cand->kind == CAND_ADD && integer_onep (base_cand->stride)) { /* Y = B + (i' * 1) X = Y * c =========================== X = (B + i') * c */ base = base_cand->base_expr; index = base_cand->index; stride = stride_in; ctype = base_cand->cand_type; if (has_single_use (base_in)) savings = (base_cand->dead_savings + stmt_cost (base_cand->cand_stmt, speed)); } else if (base_cand->kind == CAND_ADD && base_cand->index == 1 && TREE_CODE (base_cand->stride) == INTEGER_CST) { /* Y = B + (1 * S), S constant X = Y * c =========================== X = (B + S) * c */ base = base_cand->base_expr; index = wi::to_widest (base_cand->stride); stride = stride_in; ctype = base_cand->cand_type; if (has_single_use (base_in)) savings = (base_cand->dead_savings + stmt_cost (base_cand->cand_stmt, speed)); } if (base_cand->next_interp) base_cand = lookup_cand (base_cand->next_interp); else base_cand = NULL; } if (!base) { /* No interpretations had anything useful to propagate, so produce X = (Y + 0) * c. */ base = base_in; index = 0; stride = stride_in; ctype = TREE_TYPE (base_in); } c = alloc_cand_and_find_basis (CAND_MULT, gs, base, index, stride, ctype, sizetype, savings); return c; } /* Given GS which is a multiply of scalar integers, make an appropriate entry in the candidate table. If this is a multiply of two SSA names, create two CAND_MULT interpretations and attempt to find a basis for each of them. Otherwise, create a single CAND_MULT and attempt to find a basis. */ static void slsr_process_mul (gimple *gs, tree rhs1, tree rhs2, bool speed) { slsr_cand_t c, c2; /* If this is a multiply of an SSA name with itself, it is highly unlikely that we will get a strength reduction opportunity, so don't record it as a candidate. This simplifies the logic for finding a basis, so if this is removed that must be considered. */ if (rhs1 == rhs2) return; if (TREE_CODE (rhs2) == SSA_NAME) { /* Record an interpretation of this statement in the candidate table assuming RHS1 is the base expression and RHS2 is the stride. */ c = create_mul_ssa_cand (gs, rhs1, rhs2, speed); /* Add the first interpretation to the statement-candidate mapping. */ add_cand_for_stmt (gs, c); /* Record another interpretation of this statement assuming RHS1 is the stride and RHS2 is the base expression. */ c2 = create_mul_ssa_cand (gs, rhs2, rhs1, speed); c->next_interp = c2->cand_num; } else { /* Record an interpretation for the multiply-immediate. */ c = create_mul_imm_cand (gs, rhs1, rhs2, speed); /* Add the interpretation to the statement-candidate mapping. */ add_cand_for_stmt (gs, c); } } /* Create a candidate entry for a statement GS, where GS adds two SSA names BASE_IN and ADDEND_IN if SUBTRACT_P is false, and subtracts ADDEND_IN from BASE_IN otherwise. Propagate any known information about the two SSA names into the new candidate. Return the new candidate. */ static slsr_cand_t create_add_ssa_cand (gimple *gs, tree base_in, tree addend_in, bool subtract_p, bool speed) { tree base = NULL_TREE, stride = NULL_TREE, ctype = NULL_TREE; tree stype = NULL_TREE; widest_int index; unsigned savings = 0; slsr_cand_t c; slsr_cand_t base_cand = base_cand_from_table (base_in); slsr_cand_t addend_cand = base_cand_from_table (addend_in); /* The most useful transformation is a multiply-immediate feeding an add or subtract. Look for that first. */ while (addend_cand && !base && addend_cand->kind != CAND_PHI) { if (addend_cand->kind == CAND_MULT && addend_cand->index == 0 && TREE_CODE (addend_cand->stride) == INTEGER_CST) { /* Z = (B + 0) * S, S constant X = Y +/- Z =========================== X = Y + ((+/-1 * S) * B) */ base = base_in; index = wi::to_widest (addend_cand->stride); if (subtract_p) index = -index; stride = addend_cand->base_expr; ctype = TREE_TYPE (base_in); stype = addend_cand->cand_type; if (has_single_use (addend_in)) savings = (addend_cand->dead_savings + stmt_cost (addend_cand->cand_stmt, speed)); } if (addend_cand->next_interp) addend_cand = lookup_cand (addend_cand->next_interp); else addend_cand = NULL; } while (base_cand && !base && base_cand->kind != CAND_PHI) { if (base_cand->kind == CAND_ADD && (base_cand->index == 0 || operand_equal_p (base_cand->stride, integer_zero_node, 0))) { /* Y = B + (i' * S), i' * S = 0 X = Y +/- Z ============================ X = B + (+/-1 * Z) */ base = base_cand->base_expr; index = subtract_p ? -1 : 1; stride = addend_in; ctype = base_cand->cand_type; stype = (TREE_CODE (addend_in) == INTEGER_CST ? sizetype : TREE_TYPE (addend_in)); if (has_single_use (base_in)) savings = (base_cand->dead_savings + stmt_cost (base_cand->cand_stmt, speed)); } else if (subtract_p) { slsr_cand_t subtrahend_cand = base_cand_from_table (addend_in); while (subtrahend_cand && !base && subtrahend_cand->kind != CAND_PHI) { if (subtrahend_cand->kind == CAND_MULT && subtrahend_cand->index == 0 && TREE_CODE (subtrahend_cand->stride) == INTEGER_CST) { /* Z = (B + 0) * S, S constant X = Y - Z =========================== Value: X = Y + ((-1 * S) * B) */ base = base_in; index = wi::to_widest (subtrahend_cand->stride); index = -index; stride = subtrahend_cand->base_expr; ctype = TREE_TYPE (base_in); stype = subtrahend_cand->cand_type; if (has_single_use (addend_in)) savings = (subtrahend_cand->dead_savings + stmt_cost (subtrahend_cand->cand_stmt, speed)); } if (subtrahend_cand->next_interp) subtrahend_cand = lookup_cand (subtrahend_cand->next_interp); else subtrahend_cand = NULL; } } if (base_cand->next_interp) base_cand = lookup_cand (base_cand->next_interp); else base_cand = NULL; } if (!base) { /* No interpretations had anything useful to propagate, so produce X = Y + (1 * Z). */ base = base_in; index = subtract_p ? -1 : 1; stride = addend_in; ctype = TREE_TYPE (base_in); stype = (TREE_CODE (addend_in) == INTEGER_CST ? sizetype : TREE_TYPE (addend_in)); } c = alloc_cand_and_find_basis (CAND_ADD, gs, base, index, stride, ctype, stype, savings); return c; } /* Create a candidate entry for a statement GS, where GS adds SSA name BASE_IN to constant INDEX_IN. Propagate any known information about BASE_IN into the new candidate. Return the new candidate. */ static slsr_cand_t create_add_imm_cand (gimple *gs, tree base_in, const widest_int &index_in, bool speed) { enum cand_kind kind = CAND_ADD; tree base = NULL_TREE, stride = NULL_TREE, ctype = NULL_TREE; tree stype = NULL_TREE; widest_int index, multiple; unsigned savings = 0; slsr_cand_t c; slsr_cand_t base_cand = base_cand_from_table (base_in); while (base_cand && !base && base_cand->kind != CAND_PHI) { signop sign = TYPE_SIGN (TREE_TYPE (base_cand->stride)); if (TREE_CODE (base_cand->stride) == INTEGER_CST && wi::multiple_of_p (index_in, wi::to_widest (base_cand->stride), sign, &multiple)) { /* Y = (B + i') * S, S constant, c = kS for some integer k X = Y + c ============================ X = (B + (i'+ k)) * S OR Y = B + (i' * S), S constant, c = kS for some integer k X = Y + c ============================ X = (B + (i'+ k)) * S */ kind = base_cand->kind; base = base_cand->base_expr; index = base_cand->index + multiple; stride = base_cand->stride; ctype = base_cand->cand_type; stype = base_cand->stride_type; if (has_single_use (base_in)) savings = (base_cand->dead_savings + stmt_cost (base_cand->cand_stmt, speed)); } if (base_cand->next_interp) base_cand = lookup_cand (base_cand->next_interp); else base_cand = NULL; } if (!base) { /* No interpretations had anything useful to propagate, so produce X = Y + (c * 1). */ kind = CAND_ADD; base = base_in; index = index_in; stride = integer_one_node; ctype = TREE_TYPE (base_in); stype = sizetype; } c = alloc_cand_and_find_basis (kind, gs, base, index, stride, ctype, stype, savings); return c; } /* Given GS which is an add or subtract of scalar integers or pointers, make at least one appropriate entry in the candidate table. */ static void slsr_process_add (gimple *gs, tree rhs1, tree rhs2, bool speed) { bool subtract_p = gimple_assign_rhs_code (gs) == MINUS_EXPR; slsr_cand_t c = NULL, c2; if (TREE_CODE (rhs2) == SSA_NAME) { /* First record an interpretation assuming RHS1 is the base expression and RHS2 is the stride. But it doesn't make sense for the stride to be a pointer, so don't record a candidate in that case. */ if (!POINTER_TYPE_P (TREE_TYPE (rhs2))) { c = create_add_ssa_cand (gs, rhs1, rhs2, subtract_p, speed); /* Add the first interpretation to the statement-candidate mapping. */ add_cand_for_stmt (gs, c); } /* If the two RHS operands are identical, or this is a subtract, we're done. */ if (operand_equal_p (rhs1, rhs2, 0) || subtract_p) return; /* Otherwise, record another interpretation assuming RHS2 is the base expression and RHS1 is the stride, again provided that the stride is not a pointer. */ if (!POINTER_TYPE_P (TREE_TYPE (rhs1))) { c2 = create_add_ssa_cand (gs, rhs2, rhs1, false, speed); if (c) c->next_interp = c2->cand_num; else add_cand_for_stmt (gs, c2); } } else { /* Record an interpretation for the add-immediate. */ widest_int index = wi::to_widest (rhs2); if (subtract_p) index = -index; c = create_add_imm_cand (gs, rhs1, index, speed); /* Add the interpretation to the statement-candidate mapping. */ add_cand_for_stmt (gs, c); } } /* Given GS which is a negate of a scalar integer, make an appropriate entry in the candidate table. A negate is equivalent to a multiply by -1. */ static void slsr_process_neg (gimple *gs, tree rhs1, bool speed) { /* Record a CAND_MULT interpretation for the multiply by -1. */ slsr_cand_t c = create_mul_imm_cand (gs, rhs1, integer_minus_one_node, speed); /* Add the interpretation to the statement-candidate mapping. */ add_cand_for_stmt (gs, c); } /* Help function for legal_cast_p, operating on two trees. Checks whether it's allowable to cast from RHS to LHS. See legal_cast_p for more details. */ static bool legal_cast_p_1 (tree lhs_type, tree rhs_type) { unsigned lhs_size, rhs_size; bool lhs_wraps, rhs_wraps; lhs_size = TYPE_PRECISION (lhs_type); rhs_size = TYPE_PRECISION (rhs_type); lhs_wraps = ANY_INTEGRAL_TYPE_P (lhs_type) && TYPE_OVERFLOW_WRAPS (lhs_type); rhs_wraps = ANY_INTEGRAL_TYPE_P (rhs_type) && TYPE_OVERFLOW_WRAPS (rhs_type); if (lhs_size < rhs_size || (rhs_wraps && !lhs_wraps) || (rhs_wraps && lhs_wraps && rhs_size != lhs_size)) return false; return true; } /* Return TRUE if GS is a statement that defines an SSA name from a conversion and is legal for us to combine with an add and multiply in the candidate table. For example, suppose we have: A = B + i; C = (type) A; D = C * S; Without the type-cast, we would create a CAND_MULT for D with base B, index i, and stride S. We want to record this candidate only if it is equivalent to apply the type cast following the multiply: A = B + i; E = A * S; D = (type) E; We will record the type with the candidate for D. This allows us to use a similar previous candidate as a basis. If we have earlier seen A' = B + i'; C' = (type) A'; D' = C' * S; we can replace D with D = D' + (i - i') * S; But if moving the type-cast would change semantics, we mustn't do this. This is legitimate for casts from a non-wrapping integral type to any integral type of the same or larger size. It is not legitimate to convert a wrapping type to a non-wrapping type, or to a wrapping type of a different size. I.e., with a wrapping type, we must assume that the addition B + i could wrap, in which case performing the multiply before or after one of the "illegal" type casts will have different semantics. */ static bool legal_cast_p (gimple *gs, tree rhs) { if (!is_gimple_assign (gs) || !CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (gs))) return false; return legal_cast_p_1 (TREE_TYPE (gimple_assign_lhs (gs)), TREE_TYPE (rhs)); } /* Given GS which is a cast to a scalar integer type, determine whether the cast is legal for strength reduction. If so, make at least one appropriate entry in the candidate table. */ static void slsr_process_cast (gimple *gs, tree rhs1, bool speed) { tree lhs, ctype; slsr_cand_t base_cand, c = NULL, c2; unsigned savings = 0; if (!legal_cast_p (gs, rhs1)) return; lhs = gimple_assign_lhs (gs); base_cand = base_cand_from_table (rhs1); ctype = TREE_TYPE (lhs); if (base_cand && base_cand->kind != CAND_PHI) { while (base_cand) { /* Propagate all data from the base candidate except the type, which comes from the cast, and the base candidate's cast, which is no longer applicable. */ if (has_single_use (rhs1)) savings = (base_cand->dead_savings + stmt_cost (base_cand->cand_stmt, speed)); c = alloc_cand_and_find_basis (base_cand->kind, gs, base_cand->base_expr, base_cand->index, base_cand->stride, ctype, base_cand->stride_type, savings); if (base_cand->next_interp) base_cand = lookup_cand (base_cand->next_interp); else base_cand = NULL; } } else { /* If nothing is known about the RHS, create fresh CAND_ADD and CAND_MULT interpretations: X = Y + (0 * 1) X = (Y + 0) * 1 The first of these is somewhat arbitrary, but the choice of 1 for the stride simplifies the logic for propagating casts into their uses. */ c = alloc_cand_and_find_basis (CAND_ADD, gs, rhs1, 0, integer_one_node, ctype, sizetype, 0); c2 = alloc_cand_and_find_basis (CAND_MULT, gs, rhs1, 0, integer_one_node, ctype, sizetype, 0); c->next_interp = c2->cand_num; } /* Add the first (or only) interpretation to the statement-candidate mapping. */ add_cand_for_stmt (gs, c); } /* Given GS which is a copy of a scalar integer type, make at least one appropriate entry in the candidate table. This interface is included for completeness, but is unnecessary if this pass immediately follows a pass that performs copy propagation, such as DOM. */ static void slsr_process_copy (gimple *gs, tree rhs1, bool speed) { slsr_cand_t base_cand, c = NULL, c2; unsigned savings = 0; base_cand = base_cand_from_table (rhs1); if (base_cand && base_cand->kind != CAND_PHI) { while (base_cand) { /* Propagate all data from the base candidate. */ if (has_single_use (rhs1)) savings = (base_cand->dead_savings + stmt_cost (base_cand->cand_stmt, speed)); c = alloc_cand_and_find_basis (base_cand->kind, gs, base_cand->base_expr, base_cand->index, base_cand->stride, base_cand->cand_type, base_cand->stride_type, savings); if (base_cand->next_interp) base_cand = lookup_cand (base_cand->next_interp); else base_cand = NULL; } } else { /* If nothing is known about the RHS, create fresh CAND_ADD and CAND_MULT interpretations: X = Y + (0 * 1) X = (Y + 0) * 1 The first of these is somewhat arbitrary, but the choice of 1 for the stride simplifies the logic for propagating casts into their uses. */ c = alloc_cand_and_find_basis (CAND_ADD, gs, rhs1, 0, integer_one_node, TREE_TYPE (rhs1), sizetype, 0); c2 = alloc_cand_and_find_basis (CAND_MULT, gs, rhs1, 0, integer_one_node, TREE_TYPE (rhs1), sizetype, 0); c->next_interp = c2->cand_num; } /* Add the first (or only) interpretation to the statement-candidate mapping. */ add_cand_for_stmt (gs, c); } class find_candidates_dom_walker : public dom_walker { public: find_candidates_dom_walker (cdi_direction direction) : dom_walker (direction) {} virtual edge before_dom_children (basic_block); }; /* Find strength-reduction candidates in block BB. */ edge find_candidates_dom_walker::before_dom_children (basic_block bb) { bool speed = optimize_bb_for_speed_p (bb); for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) slsr_process_phi (gsi.phi (), speed); for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) { gimple *gs = gsi_stmt (gsi); if (gimple_vuse (gs) && gimple_assign_single_p (gs)) slsr_process_ref (gs); else if (is_gimple_assign (gs) && (INTEGRAL_TYPE_P (TREE_TYPE (gimple_assign_lhs (gs))) || POINTER_TYPE_P (TREE_TYPE (gimple_assign_lhs (gs))))) { tree rhs1 = NULL_TREE, rhs2 = NULL_TREE; switch (gimple_assign_rhs_code (gs)) { case MULT_EXPR: case PLUS_EXPR: rhs1 = gimple_assign_rhs1 (gs); rhs2 = gimple_assign_rhs2 (gs); /* Should never happen, but currently some buggy situations in earlier phases put constants in rhs1. */ if (TREE_CODE (rhs1) != SSA_NAME) continue; break; /* Possible future opportunity: rhs1 of a ptr+ can be an ADDR_EXPR. */ case POINTER_PLUS_EXPR: case MINUS_EXPR: rhs2 = gimple_assign_rhs2 (gs); gcc_fallthrough (); CASE_CONVERT: case SSA_NAME: case NEGATE_EXPR: rhs1 = gimple_assign_rhs1 (gs); if (TREE_CODE (rhs1) != SSA_NAME) continue; break; default: ; } switch (gimple_assign_rhs_code (gs)) { case MULT_EXPR: slsr_process_mul (gs, rhs1, rhs2, speed); break; case PLUS_EXPR: case POINTER_PLUS_EXPR: case MINUS_EXPR: slsr_process_add (gs, rhs1, rhs2, speed); break; case NEGATE_EXPR: slsr_process_neg (gs, rhs1, speed); break; CASE_CONVERT: slsr_process_cast (gs, rhs1, speed); break; case SSA_NAME: slsr_process_copy (gs, rhs1, speed); break; default: ; } } } return NULL; } /* Dump a candidate for debug. */ static void dump_candidate (slsr_cand_t c) { fprintf (dump_file, "%3d [%d] ", c->cand_num, gimple_bb (c->cand_stmt)->index); print_gimple_stmt (dump_file, c->cand_stmt, 0); switch (c->kind) { case CAND_MULT: fputs (" MULT : (", dump_file); print_generic_expr (dump_file, c->base_expr); fputs (" + ", dump_file); print_decs (c->index, dump_file); fputs (") * ", dump_file); if (TREE_CODE (c->stride) != INTEGER_CST && c->stride_type != TREE_TYPE (c->stride)) { fputs ("(", dump_file); print_generic_expr (dump_file, c->stride_type); fputs (")", dump_file); } print_generic_expr (dump_file, c->stride); fputs (" : ", dump_file); break; case CAND_ADD: fputs (" ADD : ", dump_file); print_generic_expr (dump_file, c->base_expr); fputs (" + (", dump_file); print_decs (c->index, dump_file); fputs (" * ", dump_file); if (TREE_CODE (c->stride) != INTEGER_CST && c->stride_type != TREE_TYPE (c->stride)) { fputs ("(", dump_file); print_generic_expr (dump_file, c->stride_type); fputs (")", dump_file); } print_generic_expr (dump_file, c->stride); fputs (") : ", dump_file); break; case CAND_REF: fputs (" REF : ", dump_file); print_generic_expr (dump_file, c->base_expr); fputs (" + (", dump_file); print_generic_expr (dump_file, c->stride); fputs (") + ", dump_file); print_decs (c->index, dump_file); fputs (" : ", dump_file); break; case CAND_PHI: fputs (" PHI : ", dump_file); print_generic_expr (dump_file, c->base_expr); fputs (" + (unknown * ", dump_file); print_generic_expr (dump_file, c->stride); fputs (") : ", dump_file); break; default: gcc_unreachable (); } print_generic_expr (dump_file, c->cand_type); fprintf (dump_file, "\n basis: %d dependent: %d sibling: %d\n", c->basis, c->dependent, c->sibling); fprintf (dump_file, " next-interp: %d dead-savings: %d\n", c->next_interp, c->dead_savings); if (c->def_phi) fprintf (dump_file, " phi: %d\n", c->def_phi); fputs ("\n", dump_file); } /* Dump the candidate vector for debug. */ static void dump_cand_vec (void) { unsigned i; slsr_cand_t c; fprintf (dump_file, "\nStrength reduction candidate vector:\n\n"); FOR_EACH_VEC_ELT (cand_vec, i, c) dump_candidate (c); } /* Callback used to dump the candidate chains hash table. */ int ssa_base_cand_dump_callback (cand_chain **slot, void *ignored ATTRIBUTE_UNUSED) { const_cand_chain_t chain = *slot; cand_chain_t p; print_generic_expr (dump_file, chain->base_expr); fprintf (dump_file, " -> %d", chain->cand->cand_num); for (p = chain->next; p; p = p->next) fprintf (dump_file, " -> %d", p->cand->cand_num); fputs ("\n", dump_file); return 1; } /* Dump the candidate chains. */ static void dump_cand_chains (void) { fprintf (dump_file, "\nStrength reduction candidate chains:\n\n"); base_cand_map->traverse_noresize <void *, ssa_base_cand_dump_callback> (NULL); fputs ("\n", dump_file); } /* Dump the increment vector for debug. */ static void dump_incr_vec (void) { if (dump_file && (dump_flags & TDF_DETAILS)) { unsigned i; fprintf (dump_file, "\nIncrement vector:\n\n"); for (i = 0; i < incr_vec_len; i++) { fprintf (dump_file, "%3d increment: ", i); print_decs (incr_vec[i].incr, dump_file); fprintf (dump_file, "\n count: %d", incr_vec[i].count); fprintf (dump_file, "\n cost: %d", incr_vec[i].cost); fputs ("\n initializer: ", dump_file); print_generic_expr (dump_file, incr_vec[i].initializer); fputs ("\n\n", dump_file); } } } /* Replace *EXPR in candidate C with an equivalent strength-reduced data reference. */ static void replace_ref (tree *expr, slsr_cand_t c) { tree add_expr, mem_ref, acc_type = TREE_TYPE (*expr); unsigned HOST_WIDE_INT misalign; unsigned align; /* Ensure the memory reference carries the minimum alignment requirement for the data type. See PR58041. */ get_object_alignment_1 (*expr, &align, &misalign); if (misalign != 0) align = least_bit_hwi (misalign); if (align < TYPE_ALIGN (acc_type)) acc_type = build_aligned_type (acc_type, align); add_expr = fold_build2 (POINTER_PLUS_EXPR, c->cand_type, c->base_expr, c->stride); mem_ref = fold_build2 (MEM_REF, acc_type, add_expr, wide_int_to_tree (c->cand_type, c->index)); /* Gimplify the base addressing expression for the new MEM_REF tree. */ gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt); TREE_OPERAND (mem_ref, 0) = force_gimple_operand_gsi (&gsi, TREE_OPERAND (mem_ref, 0), /*simple_p=*/true, NULL, /*before=*/true, GSI_SAME_STMT); copy_ref_info (mem_ref, *expr); *expr = mem_ref; update_stmt (c->cand_stmt); } /* Replace CAND_REF candidate C, each sibling of candidate C, and each dependent of candidate C with an equivalent strength-reduced data reference. */ static void replace_refs (slsr_cand_t c) { if (dump_file && (dump_flags & TDF_DETAILS)) { fputs ("Replacing reference: ", dump_file); print_gimple_stmt (dump_file, c->cand_stmt, 0); } if (gimple_vdef (c->cand_stmt)) { tree *lhs = gimple_assign_lhs_ptr (c->cand_stmt); replace_ref (lhs, c); } else { tree *rhs = gimple_assign_rhs1_ptr (c->cand_stmt); replace_ref (rhs, c); } if (dump_file && (dump_flags & TDF_DETAILS)) { fputs ("With: ", dump_file); print_gimple_stmt (dump_file, c->cand_stmt, 0); fputs ("\n", dump_file); } if (c->sibling) replace_refs (lookup_cand (c->sibling)); if (c->dependent) replace_refs (lookup_cand (c->dependent)); } /* Return TRUE if candidate C is dependent upon a PHI. */ static bool phi_dependent_cand_p (slsr_cand_t c) { /* A candidate is not necessarily dependent upon a PHI just because it has a phi definition for its base name. It may have a basis that relies upon the same phi definition, in which case the PHI is irrelevant to this candidate. */ return (c->def_phi && c->basis && lookup_cand (c->basis)->def_phi != c->def_phi); } /* Calculate the increment required for candidate C relative to its basis. */ static widest_int cand_increment (slsr_cand_t c) { slsr_cand_t basis; /* If the candidate doesn't have a basis, just return its own index. This is useful in record_increments to help us find an existing initializer. Also, if the candidate's basis is hidden by a phi, then its own index will be the increment from the newly introduced phi basis. */ if (!c->basis || phi_dependent_cand_p (c)) return c->index; basis = lookup_cand (c->basis); gcc_assert (operand_equal_p (c->base_expr, basis->base_expr, 0)); return c->index - basis->index; } /* Calculate the increment required for candidate C relative to its basis. If we aren't going to generate pointer arithmetic for this candidate, return the absolute value of that increment instead. */ static inline widest_int cand_abs_increment (slsr_cand_t c) { widest_int increment = cand_increment (c); if (!address_arithmetic_p && wi::neg_p (increment)) increment = -increment; return increment; } /* Return TRUE iff candidate C has already been replaced under another interpretation. */ static inline bool cand_already_replaced (slsr_cand_t c) { return (gimple_bb (c->cand_stmt) == 0); } /* Common logic used by replace_unconditional_candidate and replace_conditional_candidate. */ static void replace_mult_candidate (slsr_cand_t c, tree basis_name, widest_int bump) { tree target_type = TREE_TYPE (gimple_assign_lhs (c->cand_stmt)); enum tree_code cand_code = gimple_assign_rhs_code (c->cand_stmt); /* It is not useful to replace casts, copies, negates, or adds of an SSA name and a constant. */ if (cand_code == SSA_NAME || CONVERT_EXPR_CODE_P (cand_code) || cand_code == PLUS_EXPR || cand_code == POINTER_PLUS_EXPR || cand_code == MINUS_EXPR || cand_code == NEGATE_EXPR) return; enum tree_code code = PLUS_EXPR; tree bump_tree; gimple *stmt_to_print = NULL; if (wi::neg_p (bump)) { code = MINUS_EXPR; bump = -bump; } /* It is possible that the resulting bump doesn't fit in target_type. Abandon the replacement in this case. This does not affect siblings or dependents of C. */ if (bump != wi::ext (bump, TYPE_PRECISION (target_type), TYPE_SIGN (target_type))) return; bump_tree = wide_int_to_tree (target_type, bump); /* If the basis name and the candidate's LHS have incompatible types, introduce a cast. */ if (!useless_type_conversion_p (target_type, TREE_TYPE (basis_name))) basis_name = introduce_cast_before_cand (c, target_type, basis_name); if (dump_file && (dump_flags & TDF_DETAILS)) { fputs ("Replacing: ", dump_file); print_gimple_stmt (dump_file, c->cand_stmt, 0); } if (bump == 0) { tree lhs = gimple_assign_lhs (c->cand_stmt); gassign *copy_stmt = gimple_build_assign (lhs, basis_name); gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt); slsr_cand_t cc = c; gimple_set_location (copy_stmt, gimple_location (c->cand_stmt)); gsi_replace (&gsi, copy_stmt, false); c->cand_stmt = copy_stmt; while (cc->next_interp) { cc = lookup_cand (cc->next_interp); cc->cand_stmt = copy_stmt; } if (dump_file && (dump_flags & TDF_DETAILS)) stmt_to_print = copy_stmt; } else { tree rhs1, rhs2; if (cand_code != NEGATE_EXPR) { rhs1 = gimple_assign_rhs1 (c->cand_stmt); rhs2 = gimple_assign_rhs2 (c->cand_stmt); } if (cand_code != NEGATE_EXPR && ((operand_equal_p (rhs1, basis_name, 0) && operand_equal_p (rhs2, bump_tree, 0)) || (operand_equal_p (rhs1, bump_tree, 0) && operand_equal_p (rhs2, basis_name, 0)))) { if (dump_file && (dump_flags & TDF_DETAILS)) { fputs ("(duplicate, not actually replacing)", dump_file); stmt_to_print = c->cand_stmt; } } else { gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt); slsr_cand_t cc = c; gimple_assign_set_rhs_with_ops (&gsi, code, basis_name, bump_tree); update_stmt (gsi_stmt (gsi)); c->cand_stmt = gsi_stmt (gsi); while (cc->next_interp) { cc = lookup_cand (cc->next_interp); cc->cand_stmt = gsi_stmt (gsi); } if (dump_file && (dump_flags & TDF_DETAILS)) stmt_to_print = gsi_stmt (gsi); } } if (dump_file && (dump_flags & TDF_DETAILS)) { fputs ("With: ", dump_file); print_gimple_stmt (dump_file, stmt_to_print, 0); fputs ("\n", dump_file); } } /* Replace candidate C with an add or subtract. Note that we only operate on CAND_MULTs with known strides, so we will never generate a POINTER_PLUS_EXPR. Each candidate X = (B + i) * S is replaced by X = Y + ((i - i') * S), as described in the module commentary. The folded value ((i - i') * S) is referred to here as the "bump." */ static void replace_unconditional_candidate (slsr_cand_t c) { slsr_cand_t basis; if (cand_already_replaced (c)) return; basis = lookup_cand (c->basis); widest_int bump = cand_increment (c) * wi::to_widest (c->stride); replace_mult_candidate (c, gimple_assign_lhs (basis->cand_stmt), bump); } /* Return the index in the increment vector of the given INCREMENT, or -1 if not found. The latter can occur if more than MAX_INCR_VEC_LEN increments have been found. */ static inline int incr_vec_index (const widest_int &increment) { unsigned i; for (i = 0; i < incr_vec_len && increment != incr_vec[i].incr; i++) ; if (i < incr_vec_len) return i; else return -1; } /* Create a new statement along edge E to add BASIS_NAME to the product of INCREMENT and the stride of candidate C. Create and return a new SSA name from *VAR to be used as the LHS of the new statement. KNOWN_STRIDE is true iff C's stride is a constant. */ static tree create_add_on_incoming_edge (slsr_cand_t c, tree basis_name, widest_int increment, edge e, location_t loc, bool known_stride) { tree lhs, basis_type; gassign *new_stmt, *cast_stmt = NULL; /* If the add candidate along this incoming edge has the same index as C's hidden basis, the hidden basis represents this edge correctly. */ if (increment == 0) return basis_name; basis_type = TREE_TYPE (basis_name); lhs = make_temp_ssa_name (basis_type, NULL, "slsr"); /* Occasionally people convert integers to pointers without a cast, leading us into trouble if we aren't careful. */ enum tree_code plus_code = POINTER_TYPE_P (basis_type) ? POINTER_PLUS_EXPR : PLUS_EXPR; if (known_stride) { tree bump_tree; enum tree_code code = plus_code; widest_int bump = increment * wi::to_widest (c->stride); if (wi::neg_p (bump) && !POINTER_TYPE_P (basis_type)) { code = MINUS_EXPR; bump = -bump; } tree stride_type = POINTER_TYPE_P (basis_type) ? sizetype : basis_type; bump_tree = wide_int_to_tree (stride_type, bump); new_stmt = gimple_build_assign (lhs, code, basis_name, bump_tree); } else { int i; bool negate_incr = !POINTER_TYPE_P (basis_type) && wi::neg_p (increment); i = incr_vec_index (negate_incr ? -increment : increment); gcc_assert (i >= 0); if (incr_vec[i].initializer) { enum tree_code code = negate_incr ? MINUS_EXPR : plus_code; new_stmt = gimple_build_assign (lhs, code, basis_name, incr_vec[i].initializer); } else { tree stride; if (!types_compatible_p (TREE_TYPE (c->stride), c->stride_type)) { tree cast_stride = make_temp_ssa_name (c->stride_type, NULL, "slsr"); cast_stmt = gimple_build_assign (cast_stride, NOP_EXPR, c->stride); stride = cast_stride; } else stride = c->stride; if (increment == 1) new_stmt = gimple_build_assign (lhs, plus_code, basis_name, stride); else if (increment == -1) new_stmt = gimple_build_assign (lhs, MINUS_EXPR, basis_name, stride); else gcc_unreachable (); } } if (cast_stmt) { gimple_set_location (cast_stmt, loc); gsi_insert_on_edge (e, cast_stmt); } gimple_set_location (new_stmt, loc); gsi_insert_on_edge (e, new_stmt); if (dump_file && (dump_flags & TDF_DETAILS)) { if (cast_stmt) { fprintf (dump_file, "Inserting cast on edge %d->%d: ", e->src->index, e->dest->index); print_gimple_stmt (dump_file, cast_stmt, 0); } fprintf (dump_file, "Inserting on edge %d->%d: ", e->src->index, e->dest->index); print_gimple_stmt (dump_file, new_stmt, 0); } return lhs; } /* Clear the visited field for a tree of PHI candidates. */ static void clear_visited (gphi *phi) { unsigned i; slsr_cand_t phi_cand = *stmt_cand_map->get (phi); if (phi_cand->visited) { phi_cand->visited = 0; for (i = 0; i < gimple_phi_num_args (phi); i++) { tree arg = gimple_phi_arg_def (phi, i); gimple *arg_def = SSA_NAME_DEF_STMT (arg); if (gimple_code (arg_def) == GIMPLE_PHI) clear_visited (as_a <gphi *> (arg_def)); } } } /* Recursive helper function for create_phi_basis. */ static tree create_phi_basis_1 (slsr_cand_t c, gimple *from_phi, tree basis_name, location_t loc, bool known_stride) { int i; tree name, phi_arg; gphi *phi; slsr_cand_t basis = lookup_cand (c->basis); int nargs = gimple_phi_num_args (from_phi); basic_block phi_bb = gimple_bb (from_phi); slsr_cand_t phi_cand = *stmt_cand_map->get (from_phi); auto_vec<tree> phi_args (nargs); if (phi_cand->visited) return phi_cand->cached_basis; phi_cand->visited = 1; /* Process each argument of the existing phi that represents conditionally-executed add candidates. */ for (i = 0; i < nargs; i++) { edge e = (*phi_bb->preds)[i]; tree arg = gimple_phi_arg_def (from_phi, i); tree feeding_def; /* If the phi argument is the base name of the CAND_PHI, then this incoming arc should use the hidden basis. */ if (operand_equal_p (arg, phi_cand->base_expr, 0)) if (basis->index == 0) feeding_def = gimple_assign_lhs (basis->cand_stmt); else { widest_int incr = -basis->index; feeding_def = create_add_on_incoming_edge (c, basis_name, incr, e, loc, known_stride); } else { gimple *arg_def = SSA_NAME_DEF_STMT (arg); /* If there is another phi along this incoming edge, we must process it in the same fashion to ensure that all basis adjustments are made along its incoming edges. */ if (gimple_code (arg_def) == GIMPLE_PHI) feeding_def = create_phi_basis_1 (c, arg_def, basis_name, loc, known_stride); else { slsr_cand_t arg_cand = base_cand_from_table (arg); widest_int diff = arg_cand->index - basis->index; feeding_def = create_add_on_incoming_edge (c, basis_name, diff, e, loc, known_stride); } } /* Because of recursion, we need to save the arguments in a vector so we can create the PHI statement all at once. Otherwise the storage for the half-created PHI can be reclaimed. */ phi_args.safe_push (feeding_def); } /* Create the new phi basis. */ name = make_temp_ssa_name (TREE_TYPE (basis_name), NULL, "slsr"); phi = create_phi_node (name, phi_bb); SSA_NAME_DEF_STMT (name) = phi; FOR_EACH_VEC_ELT (phi_args, i, phi_arg) { edge e = (*phi_bb->preds)[i]; add_phi_arg (phi, phi_arg, e, loc); } update_stmt (phi); if (dump_file && (dump_flags & TDF_DETAILS)) { fputs ("Introducing new phi basis: ", dump_file); print_gimple_stmt (dump_file, phi, 0); } phi_cand->cached_basis = name; return name; } /* Given a candidate C with BASIS_NAME being the LHS of C's basis which is hidden by the phi node FROM_PHI, create a new phi node in the same block as FROM_PHI. The new phi is suitable for use as a basis by C, with its phi arguments representing conditional adjustments to the hidden basis along conditional incoming paths. Those adjustments are made by creating add statements (and sometimes recursively creating phis) along those incoming paths. LOC is the location to attach to the introduced statements. KNOWN_STRIDE is true iff C's stride is a constant. */ static tree create_phi_basis (slsr_cand_t c, gimple *from_phi, tree basis_name, location_t loc, bool known_stride) { tree retval = create_phi_basis_1 (c, from_phi, basis_name, loc, known_stride); gcc_assert (retval); clear_visited (as_a <gphi *> (from_phi)); return retval; } /* Given a candidate C whose basis is hidden by at least one intervening phi, introduce a matching number of new phis to represent its basis adjusted by conditional increments along possible incoming paths. Then replace C as though it were an unconditional candidate, using the new basis. */ static void replace_conditional_candidate (slsr_cand_t c) { tree basis_name, name; slsr_cand_t basis; location_t loc; /* Look up the LHS SSA name from C's basis. This will be the RHS1 of the adds we will introduce to create new phi arguments. */ basis = lookup_cand (c->basis); basis_name = gimple_assign_lhs (basis->cand_stmt); /* Create a new phi statement which will represent C's true basis after the transformation is complete. */ loc = gimple_location (c->cand_stmt); name = create_phi_basis (c, lookup_cand (c->def_phi)->cand_stmt, basis_name, loc, KNOWN_STRIDE); /* Replace C with an add of the new basis phi and a constant. */ widest_int bump = c->index * wi::to_widest (c->stride); replace_mult_candidate (c, name, bump); } /* Recursive helper function for phi_add_costs. SPREAD is a measure of how many PHI nodes we have visited at this point in the tree walk. */ static int phi_add_costs_1 (gimple *phi, slsr_cand_t c, int one_add_cost, int *spread) { unsigned i; int cost = 0; slsr_cand_t phi_cand = *stmt_cand_map->get (phi); if (phi_cand->visited) return 0; phi_cand->visited = 1; (*spread)++; /* If we work our way back to a phi that isn't dominated by the hidden basis, this isn't a candidate for replacement. Indicate this by returning an unreasonably high cost. It's not easy to detect these situations when determining the basis, so we defer the decision until now. */ basic_block phi_bb = gimple_bb (phi); slsr_cand_t basis = lookup_cand (c->basis); basic_block basis_bb = gimple_bb (basis->cand_stmt); if (phi_bb == basis_bb || !dominated_by_p (CDI_DOMINATORS, phi_bb, basis_bb)) return COST_INFINITE; for (i = 0; i < gimple_phi_num_args (phi); i++) { tree arg = gimple_phi_arg_def (phi, i); if (arg != phi_cand->base_expr) { gimple *arg_def = SSA_NAME_DEF_STMT (arg); if (gimple_code (arg_def) == GIMPLE_PHI) { cost += phi_add_costs_1 (arg_def, c, one_add_cost, spread); if (cost >= COST_INFINITE || *spread > MAX_SPREAD) return COST_INFINITE; } else { slsr_cand_t arg_cand = base_cand_from_table (arg); if (arg_cand->index != c->index) cost += one_add_cost; } } } return cost; } /* Compute the expected costs of inserting basis adjustments for candidate C with phi-definition PHI. The cost of inserting one adjustment is given by ONE_ADD_COST. If PHI has arguments which are themselves phi results, recursively calculate costs for those phis as well. */ static int phi_add_costs (gimple *phi, slsr_cand_t c, int one_add_cost) { int spread = 0; int retval = phi_add_costs_1 (phi, c, one_add_cost, &spread); clear_visited (as_a <gphi *> (phi)); return retval; } /* For candidate C, each sibling of candidate C, and each dependent of candidate C, determine whether the candidate is dependent upon a phi that hides its basis. If not, replace the candidate unconditionally. Otherwise, determine whether the cost of introducing compensation code for the candidate is offset by the gains from strength reduction. If so, replace the candidate and introduce the compensation code. */ static void replace_uncond_cands_and_profitable_phis (slsr_cand_t c) { if (phi_dependent_cand_p (c)) { /* A multiply candidate with a stride of 1 is just an artifice of a copy or cast; there is no value in replacing it. */ if (c->kind == CAND_MULT && wi::to_widest (c->stride) != 1) { /* A candidate dependent upon a phi will replace a multiply by a constant with an add, and will insert at most one add for each phi argument. Add these costs with the potential dead-code savings to determine profitability. */ bool speed = optimize_bb_for_speed_p (gimple_bb (c->cand_stmt)); int mult_savings = stmt_cost (c->cand_stmt, speed); gimple *phi = lookup_cand (c->def_phi)->cand_stmt; tree phi_result = gimple_phi_result (phi); int one_add_cost = add_cost (speed, TYPE_MODE (TREE_TYPE (phi_result))); int add_costs = one_add_cost + phi_add_costs (phi, c, one_add_cost); int cost = add_costs - mult_savings - c->dead_savings; if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " Conditional candidate %d:\n", c->cand_num); fprintf (dump_file, " add_costs = %d\n", add_costs); fprintf (dump_file, " mult_savings = %d\n", mult_savings); fprintf (dump_file, " dead_savings = %d\n", c->dead_savings); fprintf (dump_file, " cost = %d\n", cost); if (cost <= COST_NEUTRAL) fputs (" Replacing...\n", dump_file); else fputs (" Not replaced.\n", dump_file); } if (cost <= COST_NEUTRAL) replace_conditional_candidate (c); } } else replace_unconditional_candidate (c); if (c->sibling) replace_uncond_cands_and_profitable_phis (lookup_cand (c->sibling)); if (c->dependent) replace_uncond_cands_and_profitable_phis (lookup_cand (c->dependent)); } /* Count the number of candidates in the tree rooted at C that have not already been replaced under other interpretations. */ static int count_candidates (slsr_cand_t c) { unsigned count = cand_already_replaced (c) ? 0 : 1; if (c->sibling) count += count_candidates (lookup_cand (c->sibling)); if (c->dependent) count += count_candidates (lookup_cand (c->dependent)); return count; } /* Increase the count of INCREMENT by one in the increment vector. INCREMENT is associated with candidate C. If INCREMENT is to be conditionally executed as part of a conditional candidate replacement, IS_PHI_ADJUST is true, otherwise false. If an initializer T_0 = stride * I is provided by a candidate that dominates all candidates with the same increment, also record T_0 for subsequent use. */ static void record_increment (slsr_cand_t c, widest_int increment, bool is_phi_adjust) { bool found = false; unsigned i; /* Treat increments that differ only in sign as identical so as to share initializers, unless we are generating pointer arithmetic. */ if (!address_arithmetic_p && wi::neg_p (increment)) increment = -increment; for (i = 0; i < incr_vec_len; i++) { if (incr_vec[i].incr == increment) { incr_vec[i].count++; found = true; /* If we previously recorded an initializer that doesn't dominate this candidate, it's not going to be useful to us after all. */ if (incr_vec[i].initializer && !dominated_by_p (CDI_DOMINATORS, gimple_bb (c->cand_stmt), incr_vec[i].init_bb)) { incr_vec[i].initializer = NULL_TREE; incr_vec[i].init_bb = NULL; } break; } } if (!found && incr_vec_len < MAX_INCR_VEC_LEN - 1) { /* The first time we see an increment, create the entry for it. If this is the root candidate which doesn't have a basis, set the count to zero. We're only processing it so it can possibly provide an initializer for other candidates. */ incr_vec[incr_vec_len].incr = increment; incr_vec[incr_vec_len].count = c->basis || is_phi_adjust ? 1 : 0; incr_vec[incr_vec_len].cost = COST_INFINITE; /* Optimistically record the first occurrence of this increment as providing an initializer (if it does); we will revise this opinion later if it doesn't dominate all other occurrences. Exception: increments of 0, 1 never need initializers; and phi adjustments don't ever provide initializers. */ if (c->kind == CAND_ADD && !is_phi_adjust && c->index == increment && (increment > 1 || increment < 0) && (gimple_assign_rhs_code (c->cand_stmt) == PLUS_EXPR || gimple_assign_rhs_code (c->cand_stmt) == POINTER_PLUS_EXPR)) { tree t0 = NULL_TREE; tree rhs1 = gimple_assign_rhs1 (c->cand_stmt); tree rhs2 = gimple_assign_rhs2 (c->cand_stmt); if (operand_equal_p (rhs1, c->base_expr, 0)) t0 = rhs2; else if (operand_equal_p (rhs2, c->base_expr, 0)) t0 = rhs1; if (t0 && SSA_NAME_DEF_STMT (t0) && gimple_bb (SSA_NAME_DEF_STMT (t0))) { incr_vec[incr_vec_len].initializer = t0; incr_vec[incr_vec_len++].init_bb = gimple_bb (SSA_NAME_DEF_STMT (t0)); } else { incr_vec[incr_vec_len].initializer = NULL_TREE; incr_vec[incr_vec_len++].init_bb = NULL; } } else { incr_vec[incr_vec_len].initializer = NULL_TREE; incr_vec[incr_vec_len++].init_bb = NULL; } } } /* Recursive helper function for record_phi_increments. */ static void record_phi_increments_1 (slsr_cand_t basis, gimple *phi) { unsigned i; slsr_cand_t phi_cand = *stmt_cand_map->get (phi); if (phi_cand->visited) return; phi_cand->visited = 1; for (i = 0; i < gimple_phi_num_args (phi); i++) { tree arg = gimple_phi_arg_def (phi, i); if (!operand_equal_p (arg, phi_cand->base_expr, 0)) { gimple *arg_def = SSA_NAME_DEF_STMT (arg); if (gimple_code (arg_def) == GIMPLE_PHI) record_phi_increments_1 (basis, arg_def); else { slsr_cand_t arg_cand = base_cand_from_table (arg); widest_int diff = arg_cand->index - basis->index; record_increment (arg_cand, diff, PHI_ADJUST); } } } } /* Given phi statement PHI that hides a candidate from its BASIS, find the increments along each incoming arc (recursively handling additional phis that may be present) and record them. These increments are the difference in index between the index-adjusting statements and the index of the basis. */ static void record_phi_increments (slsr_cand_t basis, gimple *phi) { record_phi_increments_1 (basis, phi); clear_visited (as_a <gphi *> (phi)); } /* Determine how many times each unique increment occurs in the set of candidates rooted at C's parent, recording the data in the increment vector. For each unique increment I, if an initializer T_0 = stride * I is provided by a candidate that dominates all candidates with the same increment, also record T_0 for subsequent use. */ static void record_increments (slsr_cand_t c) { if (!cand_already_replaced (c)) { if (!phi_dependent_cand_p (c)) record_increment (c, cand_increment (c), NOT_PHI_ADJUST); else { /* A candidate with a basis hidden by a phi will have one increment for its relationship to the index represented by the phi, and potentially additional increments along each incoming edge. For the root of the dependency tree (which has no basis), process just the initial index in case it has an initializer that can be used by subsequent candidates. */ record_increment (c, c->index, NOT_PHI_ADJUST); if (c->basis) record_phi_increments (lookup_cand (c->basis), lookup_cand (c->def_phi)->cand_stmt); } } if (c->sibling) record_increments (lookup_cand (c->sibling)); if (c->dependent) record_increments (lookup_cand (c->dependent)); } /* Recursive helper function for phi_incr_cost. */ static int phi_incr_cost_1 (slsr_cand_t c, const widest_int &incr, gimple *phi, int *savings) { unsigned i; int cost = 0; slsr_cand_t basis = lookup_cand (c->basis); slsr_cand_t phi_cand = *stmt_cand_map->get (phi); if (phi_cand->visited) return 0; phi_cand->visited = 1; for (i = 0; i < gimple_phi_num_args (phi); i++) { tree arg = gimple_phi_arg_def (phi, i); if (!operand_equal_p (arg, phi_cand->base_expr, 0)) { gimple *arg_def = SSA_NAME_DEF_STMT (arg); if (gimple_code (arg_def) == GIMPLE_PHI) { int feeding_savings = 0; tree feeding_var = gimple_phi_result (arg_def); cost += phi_incr_cost_1 (c, incr, arg_def, &feeding_savings); if (uses_consumed_by_stmt (feeding_var, phi)) *savings += feeding_savings; } else { slsr_cand_t arg_cand = base_cand_from_table (arg); widest_int diff = arg_cand->index - basis->index; if (incr == diff) { tree basis_lhs = gimple_assign_lhs (basis->cand_stmt); tree lhs = gimple_assign_lhs (arg_cand->cand_stmt); cost += add_cost (true, TYPE_MODE (TREE_TYPE (basis_lhs))); if (uses_consumed_by_stmt (lhs, phi)) *savings += stmt_cost (arg_cand->cand_stmt, true); } } } } return cost; } /* Add up and return the costs of introducing add statements that require the increment INCR on behalf of candidate C and phi statement PHI. Accumulate into *SAVINGS the potential savings from removing existing statements that feed PHI and have no other uses. */ static int phi_incr_cost (slsr_cand_t c, const widest_int &incr, gimple *phi, int *savings) { int retval = phi_incr_cost_1 (c, incr, phi, savings); clear_visited (as_a <gphi *> (phi)); return retval; } /* Return the first candidate in the tree rooted at C that has not already been replaced, favoring siblings over dependents. */ static slsr_cand_t unreplaced_cand_in_tree (slsr_cand_t c) { if (!cand_already_replaced (c)) return c; if (c->sibling) { slsr_cand_t sib = unreplaced_cand_in_tree (lookup_cand (c->sibling)); if (sib) return sib; } if (c->dependent) { slsr_cand_t dep = unreplaced_cand_in_tree (lookup_cand (c->dependent)); if (dep) return dep; } return NULL; } /* Return TRUE if the candidates in the tree rooted at C should be optimized for speed, else FALSE. We estimate this based on the block containing the most dominant candidate in the tree that has not yet been replaced. */ static bool optimize_cands_for_speed_p (slsr_cand_t c) { slsr_cand_t c2 = unreplaced_cand_in_tree (c); gcc_assert (c2); return optimize_bb_for_speed_p (gimple_bb (c2->cand_stmt)); } /* Add COST_IN to the lowest cost of any dependent path starting at candidate C or any of its siblings, counting only candidates along such paths with increment INCR. Assume that replacing a candidate reduces cost by REPL_SAVINGS. Also account for savings from any statements that would go dead. If COUNT_PHIS is true, include costs of introducing feeding statements for conditional candidates. */ static int lowest_cost_path (int cost_in, int repl_savings, slsr_cand_t c, const widest_int &incr, bool count_phis) { int local_cost, sib_cost, savings = 0; widest_int cand_incr = cand_abs_increment (c); if (cand_already_replaced (c)) local_cost = cost_in; else if (incr == cand_incr) local_cost = cost_in - repl_savings - c->dead_savings; else local_cost = cost_in - c->dead_savings; if (count_phis && phi_dependent_cand_p (c) && !cand_already_replaced (c)) { gimple *phi = lookup_cand (c->def_phi)->cand_stmt; local_cost += phi_incr_cost (c, incr, phi, &savings); if (uses_consumed_by_stmt (gimple_phi_result (phi), c->cand_stmt)) local_cost -= savings; } if (c->dependent) local_cost = lowest_cost_path (local_cost, repl_savings, lookup_cand (c->dependent), incr, count_phis); if (c->sibling) { sib_cost = lowest_cost_path (cost_in, repl_savings, lookup_cand (c->sibling), incr, count_phis); local_cost = MIN (local_cost, sib_cost); } return local_cost; } /* Compute the total savings that would accrue from all replacements in the candidate tree rooted at C, counting only candidates with increment INCR. Assume that replacing a candidate reduces cost by REPL_SAVINGS. Also account for savings from statements that would go dead. */ static int total_savings (int repl_savings, slsr_cand_t c, const widest_int &incr, bool count_phis) { int savings = 0; widest_int cand_incr = cand_abs_increment (c); if (incr == cand_incr && !cand_already_replaced (c)) savings += repl_savings + c->dead_savings; if (count_phis && phi_dependent_cand_p (c) && !cand_already_replaced (c)) { int phi_savings = 0; gimple *phi = lookup_cand (c->def_phi)->cand_stmt; savings -= phi_incr_cost (c, incr, phi, &phi_savings); if (uses_consumed_by_stmt (gimple_phi_result (phi), c->cand_stmt)) savings += phi_savings; } if (c->dependent) savings += total_savings (repl_savings, lookup_cand (c->dependent), incr, count_phis); if (c->sibling) savings += total_savings (repl_savings, lookup_cand (c->sibling), incr, count_phis); return savings; } /* Use target-specific costs to determine and record which increments in the current candidate tree are profitable to replace, assuming MODE and SPEED. FIRST_DEP is the first dependent of the root of the candidate tree. One slight limitation here is that we don't account for the possible introduction of casts in some cases. See replace_one_candidate for the cases where these are introduced. This should probably be cleaned up sometime. */ static void analyze_increments (slsr_cand_t first_dep, machine_mode mode, bool speed) { unsigned i; for (i = 0; i < incr_vec_len; i++) { HOST_WIDE_INT incr = incr_vec[i].incr.to_shwi (); /* If somehow this increment is bigger than a HWI, we won't be optimizing candidates that use it. And if the increment has a count of zero, nothing will be done with it. */ if (!wi::fits_shwi_p (incr_vec[i].incr) || !incr_vec[i].count) incr_vec[i].cost = COST_INFINITE; /* Increments of 0, 1, and -1 are always profitable to replace, because they always replace a multiply or add with an add or copy, and may cause one or more existing instructions to go dead. Exception: -1 can't be assumed to be profitable for pointer addition. */ else if (incr == 0 || incr == 1 || (incr == -1 && !POINTER_TYPE_P (first_dep->cand_type))) incr_vec[i].cost = COST_NEUTRAL; /* If we need to add an initializer, give up if a cast from the candidate's type to its stride's type can lose precision. Note that this already takes into account that the stride may have been cast to a wider type, in which case this test won't fire. Example: short int _1; _2 = (int) _1; _3 = _2 * 10; _4 = x + _3; ADD: x + (10 * (int)_1) : int _5 = _2 * 15; _6 = x + _5; ADD: x + (15 * (int)_1) : int Although the stride was a short int initially, the stride used in the analysis has been widened to an int, and such widening will be done in the initializer as well. */ else if (!incr_vec[i].initializer && TREE_CODE (first_dep->stride) != INTEGER_CST && !legal_cast_p_1 (first_dep->stride_type, TREE_TYPE (gimple_assign_lhs (first_dep->cand_stmt)))) incr_vec[i].cost = COST_INFINITE; /* If we need to add an initializer, make sure we don't introduce a multiply by a pointer type, which can happen in certain cast scenarios. */ else if (!incr_vec[i].initializer && TREE_CODE (first_dep->stride) != INTEGER_CST && POINTER_TYPE_P (first_dep->stride_type)) incr_vec[i].cost = COST_INFINITE; /* For any other increment, if this is a multiply candidate, we must introduce a temporary T and initialize it with T_0 = stride * increment. When optimizing for speed, walk the candidate tree to calculate the best cost reduction along any path; if it offsets the fixed cost of inserting the initializer, replacing the increment is profitable. When optimizing for size, instead calculate the total cost reduction from replacing all candidates with this increment. */ else if (first_dep->kind == CAND_MULT) { int cost = mult_by_coeff_cost (incr, mode, speed); int repl_savings = mul_cost (speed, mode) - add_cost (speed, mode); if (speed) cost = lowest_cost_path (cost, repl_savings, first_dep, incr_vec[i].incr, COUNT_PHIS); else cost -= total_savings (repl_savings, first_dep, incr_vec[i].incr, COUNT_PHIS); incr_vec[i].cost = cost; } /* If this is an add candidate, the initializer may already exist, so only calculate the cost of the initializer if it doesn't. We are replacing one add with another here, so the known replacement savings is zero. We will account for removal of dead instructions in lowest_cost_path or total_savings. */ else { int cost = 0; if (!incr_vec[i].initializer) cost = mult_by_coeff_cost (incr, mode, speed); if (speed) cost = lowest_cost_path (cost, 0, first_dep, incr_vec[i].incr, DONT_COUNT_PHIS); else cost -= total_savings (0, first_dep, incr_vec[i].incr, DONT_COUNT_PHIS); incr_vec[i].cost = cost; } } } /* Return the nearest common dominator of BB1 and BB2. If the blocks are identical, return the earlier of C1 and C2 in *WHERE. Otherwise, if the NCD matches BB1, return C1 in *WHERE; if the NCD matches BB2, return C2 in *WHERE; and if the NCD matches neither, return NULL in *WHERE. Note: It is possible for one of C1 and C2 to be NULL. */ static basic_block ncd_for_two_cands (basic_block bb1, basic_block bb2, slsr_cand_t c1, slsr_cand_t c2, slsr_cand_t *where) { basic_block ncd; if (!bb1) { *where = c2; return bb2; } if (!bb2) { *where = c1; return bb1; } ncd = nearest_common_dominator (CDI_DOMINATORS, bb1, bb2); /* If both candidates are in the same block, the earlier candidate wins. */ if (bb1 == ncd && bb2 == ncd) { if (!c1 || (c2 && c2->cand_num < c1->cand_num)) *where = c2; else *where = c1; } /* Otherwise, if one of them produced a candidate in the dominator, that one wins. */ else if (bb1 == ncd) *where = c1; else if (bb2 == ncd) *where = c2; /* If neither matches the dominator, neither wins. */ else *where = NULL; return ncd; } /* Consider all candidates that feed PHI. Find the nearest common dominator of those candidates requiring the given increment INCR. Further find and return the nearest common dominator of this result with block NCD. If the returned block contains one or more of the candidates, return the earliest candidate in the block in *WHERE. */ static basic_block ncd_with_phi (slsr_cand_t c, const widest_int &incr, gphi *phi, basic_block ncd, slsr_cand_t *where) { unsigned i; slsr_cand_t basis = lookup_cand (c->basis); slsr_cand_t phi_cand = *stmt_cand_map->get (phi); for (i = 0; i < gimple_phi_num_args (phi); i++) { tree arg = gimple_phi_arg_def (phi, i); if (!operand_equal_p (arg, phi_cand->base_expr, 0)) { gimple *arg_def = SSA_NAME_DEF_STMT (arg); if (gimple_code (arg_def) == GIMPLE_PHI) ncd = ncd_with_phi (c, incr, as_a <gphi *> (arg_def), ncd, where); else { slsr_cand_t arg_cand = base_cand_from_table (arg); widest_int diff = arg_cand->index - basis->index; basic_block pred = gimple_phi_arg_edge (phi, i)->src; if ((incr == diff) || (!address_arithmetic_p && incr == -diff)) ncd = ncd_for_two_cands (ncd, pred, *where, NULL, where); } } } return ncd; } /* Consider the candidate C together with any candidates that feed C's phi dependence (if any). Find and return the nearest common dominator of those candidates requiring the given increment INCR. If the returned block contains one or more of the candidates, return the earliest candidate in the block in *WHERE. */ static basic_block ncd_of_cand_and_phis (slsr_cand_t c, const widest_int &incr, slsr_cand_t *where) { basic_block ncd = NULL; if (cand_abs_increment (c) == incr) { ncd = gimple_bb (c->cand_stmt); *where = c; } if (phi_dependent_cand_p (c)) ncd = ncd_with_phi (c, incr, as_a <gphi *> (lookup_cand (c->def_phi)->cand_stmt), ncd, where); return ncd; } /* Consider all candidates in the tree rooted at C for which INCR represents the required increment of C relative to its basis. Find and return the basic block that most nearly dominates all such candidates. If the returned block contains one or more of the candidates, return the earliest candidate in the block in *WHERE. */ static basic_block nearest_common_dominator_for_cands (slsr_cand_t c, const widest_int &incr, slsr_cand_t *where) { basic_block sib_ncd = NULL, dep_ncd = NULL, this_ncd = NULL, ncd; slsr_cand_t sib_where = NULL, dep_where = NULL, this_where = NULL, new_where; /* First find the NCD of all siblings and dependents. */ if (c->sibling) sib_ncd = nearest_common_dominator_for_cands (lookup_cand (c->sibling), incr, &sib_where); if (c->dependent) dep_ncd = nearest_common_dominator_for_cands (lookup_cand (c->dependent), incr, &dep_where); if (!sib_ncd && !dep_ncd) { new_where = NULL; ncd = NULL; } else if (sib_ncd && !dep_ncd) { new_where = sib_where; ncd = sib_ncd; } else if (dep_ncd && !sib_ncd) { new_where = dep_where; ncd = dep_ncd; } else ncd = ncd_for_two_cands (sib_ncd, dep_ncd, sib_where, dep_where, &new_where); /* If the candidate's increment doesn't match the one we're interested in (and nor do any increments for feeding defs of a phi-dependence), then the result depends only on siblings and dependents. */ this_ncd = ncd_of_cand_and_phis (c, incr, &this_where); if (!this_ncd || cand_already_replaced (c)) { *where = new_where; return ncd; } /* Otherwise, compare this candidate with the result from all siblings and dependents. */ ncd = ncd_for_two_cands (ncd, this_ncd, new_where, this_where, where); return ncd; } /* Return TRUE if the increment indexed by INDEX is profitable to replace. */ static inline bool profitable_increment_p (unsigned index) { return (incr_vec[index].cost <= COST_NEUTRAL); } /* For each profitable increment in the increment vector not equal to 0 or 1 (or -1, for non-pointer arithmetic), find the nearest common dominator of all statements in the candidate chain rooted at C that require that increment, and insert an initializer T_0 = stride * increment at that location. Record T_0 with the increment record. */ static void insert_initializers (slsr_cand_t c) { unsigned i; for (i = 0; i < incr_vec_len; i++) { basic_block bb; slsr_cand_t where = NULL; gassign *init_stmt; gassign *cast_stmt = NULL; tree new_name, incr_tree, init_stride; widest_int incr = incr_vec[i].incr; if (!profitable_increment_p (i) || incr == 1 || (incr == -1 && (!POINTER_TYPE_P (lookup_cand (c->basis)->cand_type))) || incr == 0) continue; /* We may have already identified an existing initializer that will suffice. */ if (incr_vec[i].initializer) { if (dump_file && (dump_flags & TDF_DETAILS)) { fputs ("Using existing initializer: ", dump_file); print_gimple_stmt (dump_file, SSA_NAME_DEF_STMT (incr_vec[i].initializer), 0, 0); } continue; } /* Find the block that most closely dominates all candidates with this increment. If there is at least one candidate in that block, the earliest one will be returned in WHERE. */ bb = nearest_common_dominator_for_cands (c, incr, &where); /* If the NCD is not dominated by the block containing the definition of the stride, we can't legally insert a single initializer. Mark the increment as unprofitable so we don't make any replacements. FIXME: Multiple initializers could be placed with more analysis. */ gimple *stride_def = SSA_NAME_DEF_STMT (c->stride); basic_block stride_bb = gimple_bb (stride_def); if (stride_bb && !dominated_by_p (CDI_DOMINATORS, bb, stride_bb)) { if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "Initializer #%d cannot be legally placed\n", i); incr_vec[i].cost = COST_INFINITE; continue; } /* If the nominal stride has a different type than the recorded stride type, build a cast from the nominal stride to that type. */ if (!types_compatible_p (TREE_TYPE (c->stride), c->stride_type)) { init_stride = make_temp_ssa_name (c->stride_type, NULL, "slsr"); cast_stmt = gimple_build_assign (init_stride, NOP_EXPR, c->stride); } else init_stride = c->stride; /* Create a new SSA name to hold the initializer's value. */ new_name = make_temp_ssa_name (c->stride_type, NULL, "slsr"); incr_vec[i].initializer = new_name; /* Create the initializer and insert it in the latest possible dominating position. */ incr_tree = wide_int_to_tree (c->stride_type, incr); init_stmt = gimple_build_assign (new_name, MULT_EXPR, init_stride, incr_tree); if (where) { gimple_stmt_iterator gsi = gsi_for_stmt (where->cand_stmt); location_t loc = gimple_location (where->cand_stmt); if (cast_stmt) { gsi_insert_before (&gsi, cast_stmt, GSI_SAME_STMT); gimple_set_location (cast_stmt, loc); } gsi_insert_before (&gsi, init_stmt, GSI_SAME_STMT); gimple_set_location (init_stmt, loc); } else { gimple_stmt_iterator gsi = gsi_last_bb (bb); gimple *basis_stmt = lookup_cand (c->basis)->cand_stmt; location_t loc = gimple_location (basis_stmt); if (!gsi_end_p (gsi) && stmt_ends_bb_p (gsi_stmt (gsi))) { if (cast_stmt) { gsi_insert_before (&gsi, cast_stmt, GSI_SAME_STMT); gimple_set_location (cast_stmt, loc); } gsi_insert_before (&gsi, init_stmt, GSI_SAME_STMT); } else { if (cast_stmt) { gsi_insert_after (&gsi, cast_stmt, GSI_NEW_STMT); gimple_set_location (cast_stmt, loc); } gsi_insert_after (&gsi, init_stmt, GSI_SAME_STMT); } gimple_set_location (init_stmt, gimple_location (basis_stmt)); } if (dump_file && (dump_flags & TDF_DETAILS)) { if (cast_stmt) { fputs ("Inserting stride cast: ", dump_file); print_gimple_stmt (dump_file, cast_stmt, 0); } fputs ("Inserting initializer: ", dump_file); print_gimple_stmt (dump_file, init_stmt, 0); } } } /* Recursive helper function for all_phi_incrs_profitable. */ static bool all_phi_incrs_profitable_1 (slsr_cand_t c, gphi *phi, int *spread) { unsigned i; slsr_cand_t basis = lookup_cand (c->basis); slsr_cand_t phi_cand = *stmt_cand_map->get (phi); if (phi_cand->visited) return true; phi_cand->visited = 1; (*spread)++; /* If the basis doesn't dominate the PHI (including when the PHI is in the same block as the basis), we won't be able to create a PHI using the basis here. */ basic_block basis_bb = gimple_bb (basis->cand_stmt); basic_block phi_bb = gimple_bb (phi); if (phi_bb == basis_bb || !dominated_by_p (CDI_DOMINATORS, phi_bb, basis_bb)) return false; for (i = 0; i < gimple_phi_num_args (phi); i++) { /* If the PHI arg resides in a block not dominated by the basis, we won't be able to create a PHI using the basis here. */ basic_block pred_bb = gimple_phi_arg_edge (phi, i)->src; if (!dominated_by_p (CDI_DOMINATORS, pred_bb, basis_bb)) return false; tree arg = gimple_phi_arg_def (phi, i); if (!operand_equal_p (arg, phi_cand->base_expr, 0)) { gimple *arg_def = SSA_NAME_DEF_STMT (arg); if (gimple_code (arg_def) == GIMPLE_PHI) { if (!all_phi_incrs_profitable_1 (c, as_a <gphi *> (arg_def), spread) || *spread > MAX_SPREAD) return false; } else { int j; slsr_cand_t arg_cand = base_cand_from_table (arg); widest_int increment = arg_cand->index - basis->index; if (!address_arithmetic_p && wi::neg_p (increment)) increment = -increment; j = incr_vec_index (increment); if (dump_file && (dump_flags & TDF_DETAILS)) { fprintf (dump_file, " Conditional candidate %d, phi: ", c->cand_num); print_gimple_stmt (dump_file, phi, 0); fputs (" increment: ", dump_file); print_decs (increment, dump_file); if (j < 0) fprintf (dump_file, "\n Not replaced; incr_vec overflow.\n"); else { fprintf (dump_file, "\n cost: %d\n", incr_vec[j].cost); if (profitable_increment_p (j)) fputs (" Replacing...\n", dump_file); else fputs (" Not replaced.\n", dump_file); } } if (j < 0 || !profitable_increment_p (j)) return false; } } } return true; } /* Return TRUE iff all required increments for candidates feeding PHI are profitable (and legal!) to replace on behalf of candidate C. */ static bool all_phi_incrs_profitable (slsr_cand_t c, gphi *phi) { int spread = 0; bool retval = all_phi_incrs_profitable_1 (c, phi, &spread); clear_visited (phi); return retval; } /* Create a NOP_EXPR that copies FROM_EXPR into a new SSA name of type TO_TYPE, and insert it in front of the statement represented by candidate C. Use *NEW_VAR to create the new SSA name. Return the new SSA name. */ static tree introduce_cast_before_cand (slsr_cand_t c, tree to_type, tree from_expr) { tree cast_lhs; gassign *cast_stmt; gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt); cast_lhs = make_temp_ssa_name (to_type, NULL, "slsr"); cast_stmt = gimple_build_assign (cast_lhs, NOP_EXPR, from_expr); gimple_set_location (cast_stmt, gimple_location (c->cand_stmt)); gsi_insert_before (&gsi, cast_stmt, GSI_SAME_STMT); if (dump_file && (dump_flags & TDF_DETAILS)) { fputs (" Inserting: ", dump_file); print_gimple_stmt (dump_file, cast_stmt, 0); } return cast_lhs; } /* Replace the RHS of the statement represented by candidate C with NEW_CODE, NEW_RHS1, and NEW_RHS2, provided that to do so doesn't leave C unchanged or just interchange its operands. The original operation and operands are in OLD_CODE, OLD_RHS1, and OLD_RHS2. If the replacement was made and we are doing a details dump, return the revised statement, else NULL. */ static gimple * replace_rhs_if_not_dup (enum tree_code new_code, tree new_rhs1, tree new_rhs2, enum tree_code old_code, tree old_rhs1, tree old_rhs2, slsr_cand_t c) { if (new_code != old_code || ((!operand_equal_p (new_rhs1, old_rhs1, 0) || !operand_equal_p (new_rhs2, old_rhs2, 0)) && (!operand_equal_p (new_rhs1, old_rhs2, 0) || !operand_equal_p (new_rhs2, old_rhs1, 0)))) { gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt); slsr_cand_t cc = c; gimple_assign_set_rhs_with_ops (&gsi, new_code, new_rhs1, new_rhs2); update_stmt (gsi_stmt (gsi)); c->cand_stmt = gsi_stmt (gsi); while (cc->next_interp) { cc = lookup_cand (cc->next_interp); cc->cand_stmt = gsi_stmt (gsi); } if (dump_file && (dump_flags & TDF_DETAILS)) return gsi_stmt (gsi); } else if (dump_file && (dump_flags & TDF_DETAILS)) fputs (" (duplicate, not actually replacing)\n", dump_file); return NULL; } /* Strength-reduce the statement represented by candidate C by replacing it with an equivalent addition or subtraction. I is the index into the increment vector identifying C's increment. NEW_VAR is used to create a new SSA name if a cast needs to be introduced. BASIS_NAME is the rhs1 to use in creating the add/subtract. */ static void replace_one_candidate (slsr_cand_t c, unsigned i, tree basis_name) { gimple *stmt_to_print = NULL; tree orig_rhs1, orig_rhs2; tree rhs2; enum tree_code orig_code, repl_code; widest_int cand_incr; orig_code = gimple_assign_rhs_code (c->cand_stmt); orig_rhs1 = gimple_assign_rhs1 (c->cand_stmt); orig_rhs2 = gimple_assign_rhs2 (c->cand_stmt); cand_incr = cand_increment (c); if (dump_file && (dump_flags & TDF_DETAILS)) { fputs ("Replacing: ", dump_file); print_gimple_stmt (dump_file, c->cand_stmt, 0); stmt_to_print = c->cand_stmt; } if (address_arithmetic_p) repl_code = POINTER_PLUS_EXPR; else repl_code = PLUS_EXPR; /* If the increment has an initializer T_0, replace the candidate statement with an add of the basis name and the initializer. */ if (incr_vec[i].initializer) { tree init_type = TREE_TYPE (incr_vec[i].initializer); tree orig_type = TREE_TYPE (orig_rhs2); if (types_compatible_p (orig_type, init_type)) rhs2 = incr_vec[i].initializer; else rhs2 = introduce_cast_before_cand (c, orig_type, incr_vec[i].initializer); if (incr_vec[i].incr != cand_incr) { gcc_assert (repl_code == PLUS_EXPR); repl_code = MINUS_EXPR; } stmt_to_print = replace_rhs_if_not_dup (repl_code, basis_name, rhs2, orig_code, orig_rhs1, orig_rhs2, c); } /* Otherwise, the increment is one of -1, 0, and 1. Replace with a subtract of the stride from the basis name, a copy from the basis name, or an add of the stride to the basis name, respectively. It may be necessary to introduce a cast (or reuse an existing cast). */ else if (cand_incr == 1) { tree stride_type = TREE_TYPE (c->stride); tree orig_type = TREE_TYPE (orig_rhs2); if (types_compatible_p (orig_type, stride_type)) rhs2 = c->stride; else rhs2 = introduce_cast_before_cand (c, orig_type, c->stride); stmt_to_print = replace_rhs_if_not_dup (repl_code, basis_name, rhs2, orig_code, orig_rhs1, orig_rhs2, c); } else if (cand_incr == -1) { tree stride_type = TREE_TYPE (c->stride); tree orig_type = TREE_TYPE (orig_rhs2); gcc_assert (repl_code != POINTER_PLUS_EXPR); if (types_compatible_p (orig_type, stride_type)) rhs2 = c->stride; else rhs2 = introduce_cast_before_cand (c, orig_type, c->stride); if (orig_code != MINUS_EXPR || !operand_equal_p (basis_name, orig_rhs1, 0) || !operand_equal_p (rhs2, orig_rhs2, 0)) { gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt); slsr_cand_t cc = c; gimple_assign_set_rhs_with_ops (&gsi, MINUS_EXPR, basis_name, rhs2); update_stmt (gsi_stmt (gsi)); c->cand_stmt = gsi_stmt (gsi); while (cc->next_interp) { cc = lookup_cand (cc->next_interp); cc->cand_stmt = gsi_stmt (gsi); } if (dump_file && (dump_flags & TDF_DETAILS)) stmt_to_print = gsi_stmt (gsi); } else if (dump_file && (dump_flags & TDF_DETAILS)) fputs (" (duplicate, not actually replacing)\n", dump_file); } else if (cand_incr == 0) { tree lhs = gimple_assign_lhs (c->cand_stmt); tree lhs_type = TREE_TYPE (lhs); tree basis_type = TREE_TYPE (basis_name); if (types_compatible_p (lhs_type, basis_type)) { gassign *copy_stmt = gimple_build_assign (lhs, basis_name); gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt); slsr_cand_t cc = c; gimple_set_location (copy_stmt, gimple_location (c->cand_stmt)); gsi_replace (&gsi, copy_stmt, false); c->cand_stmt = copy_stmt; while (cc->next_interp) { cc = lookup_cand (cc->next_interp); cc->cand_stmt = copy_stmt; } if (dump_file && (dump_flags & TDF_DETAILS)) stmt_to_print = copy_stmt; } else { gimple_stmt_iterator gsi = gsi_for_stmt (c->cand_stmt); gassign *cast_stmt = gimple_build_assign (lhs, NOP_EXPR, basis_name); slsr_cand_t cc = c; gimple_set_location (cast_stmt, gimple_location (c->cand_stmt)); gsi_replace (&gsi, cast_stmt, false); c->cand_stmt = cast_stmt; while (cc->next_interp) { cc = lookup_cand (cc->next_interp); cc->cand_stmt = cast_stmt; } if (dump_file && (dump_flags & TDF_DETAILS)) stmt_to_print = cast_stmt; } } else gcc_unreachable (); if (dump_file && (dump_flags & TDF_DETAILS) && stmt_to_print) { fputs ("With: ", dump_file); print_gimple_stmt (dump_file, stmt_to_print, 0); fputs ("\n", dump_file); } } /* For each candidate in the tree rooted at C, replace it with an increment if such has been shown to be profitable. */ static void replace_profitable_candidates (slsr_cand_t c) { if (!cand_already_replaced (c)) { widest_int increment = cand_abs_increment (c); enum tree_code orig_code = gimple_assign_rhs_code (c->cand_stmt); int i; i = incr_vec_index (increment); /* Only process profitable increments. Nothing useful can be done to a cast or copy. */ if (i >= 0 && profitable_increment_p (i) && orig_code != SSA_NAME && !CONVERT_EXPR_CODE_P (orig_code)) { if (phi_dependent_cand_p (c)) { gphi *phi = as_a <gphi *> (lookup_cand (c->def_phi)->cand_stmt); if (all_phi_incrs_profitable (c, phi)) { /* Look up the LHS SSA name from C's basis. This will be the RHS1 of the adds we will introduce to create new phi arguments. */ slsr_cand_t basis = lookup_cand (c->basis); tree basis_name = gimple_assign_lhs (basis->cand_stmt); /* Create a new phi statement that will represent C's true basis after the transformation is complete. */ location_t loc = gimple_location (c->cand_stmt); tree name = create_phi_basis (c, phi, basis_name, loc, UNKNOWN_STRIDE); /* Replace C with an add of the new basis phi and the increment. */ replace_one_candidate (c, i, name); } } else { slsr_cand_t basis = lookup_cand (c->basis); tree basis_name = gimple_assign_lhs (basis->cand_stmt); replace_one_candidate (c, i, basis_name); } } } if (c->sibling) replace_profitable_candidates (lookup_cand (c->sibling)); if (c->dependent) replace_profitable_candidates (lookup_cand (c->dependent)); } /* Analyze costs of related candidates in the candidate vector, and make beneficial replacements. */ static void analyze_candidates_and_replace (void) { unsigned i; slsr_cand_t c; /* Each candidate that has a null basis and a non-null dependent is the root of a tree of related statements. Analyze each tree to determine a subset of those statements that can be replaced with maximum benefit. */ FOR_EACH_VEC_ELT (cand_vec, i, c) { slsr_cand_t first_dep; if (c->basis != 0 || c->dependent == 0) continue; if (dump_file && (dump_flags & TDF_DETAILS)) fprintf (dump_file, "\nProcessing dependency tree rooted at %d.\n", c->cand_num); first_dep = lookup_cand (c->dependent); /* If this is a chain of CAND_REFs, unconditionally replace each of them with a strength-reduced data reference. */ if (c->kind == CAND_REF) replace_refs (c); /* If the common stride of all related candidates is a known constant, each candidate without a phi-dependence can be profitably replaced. Each replaces a multiply by a single add, with the possibility that a feeding add also goes dead. A candidate with a phi-dependence is replaced only if the compensation code it requires is offset by the strength reduction savings. */ else if (TREE_CODE (c->stride) == INTEGER_CST) replace_uncond_cands_and_profitable_phis (first_dep); /* When the stride is an SSA name, it may still be profitable to replace some or all of the dependent candidates, depending on whether the introduced increments can be reused, or are less expensive to calculate than the replaced statements. */ else { machine_mode mode; bool speed; /* Determine whether we'll be generating pointer arithmetic when replacing candidates. */ address_arithmetic_p = (c->kind == CAND_ADD && POINTER_TYPE_P (c->cand_type)); /* If all candidates have already been replaced under other interpretations, nothing remains to be done. */ if (!count_candidates (c)) continue; /* Construct an array of increments for this candidate chain. */ incr_vec = XNEWVEC (incr_info, MAX_INCR_VEC_LEN); incr_vec_len = 0; record_increments (c); /* Determine which increments are profitable to replace. */ mode = TYPE_MODE (TREE_TYPE (gimple_assign_lhs (c->cand_stmt))); speed = optimize_cands_for_speed_p (c); analyze_increments (first_dep, mode, speed); /* Insert initializers of the form T_0 = stride * increment for use in profitable replacements. */ insert_initializers (first_dep); dump_incr_vec (); /* Perform the replacements. */ replace_profitable_candidates (first_dep); free (incr_vec); } } /* For conditional candidates, we may have uncommitted insertions on edges to clean up. */ gsi_commit_edge_inserts (); } namespace { const pass_data pass_data_strength_reduction = { GIMPLE_PASS, /* type */ "slsr", /* name */ OPTGROUP_NONE, /* optinfo_flags */ TV_GIMPLE_SLSR, /* tv_id */ ( PROP_cfg | PROP_ssa ), /* properties_required */ 0, /* properties_provided */ 0, /* properties_destroyed */ 0, /* todo_flags_start */ 0, /* todo_flags_finish */ }; class pass_strength_reduction : public gimple_opt_pass { public: pass_strength_reduction (gcc::context *ctxt) : gimple_opt_pass (pass_data_strength_reduction, ctxt) {} /* opt_pass methods: */ virtual bool gate (function *) { return flag_tree_slsr; } virtual unsigned int execute (function *); }; // class pass_strength_reduction unsigned pass_strength_reduction::execute (function *fun) { /* Create the obstack where candidates will reside. */ gcc_obstack_init (&cand_obstack); /* Allocate the candidate vector. */ cand_vec.create (128); /* Allocate the mapping from statements to candidate indices. */ stmt_cand_map = new hash_map<gimple *, slsr_cand_t>; /* Create the obstack where candidate chains will reside. */ gcc_obstack_init (&chain_obstack); /* Allocate the mapping from base expressions to candidate chains. */ base_cand_map = new hash_table<cand_chain_hasher> (500); /* Allocate the mapping from bases to alternative bases. */ alt_base_map = new hash_map<tree, tree>; /* Initialize the loop optimizer. We need to detect flow across back edges, and this gives us dominator information as well. */ loop_optimizer_init (AVOID_CFG_MODIFICATIONS); /* Walk the CFG in predominator order looking for strength reduction candidates. */ find_candidates_dom_walker (CDI_DOMINATORS) .walk (fun->cfg->x_entry_block_ptr); if (dump_file && (dump_flags & TDF_DETAILS)) { dump_cand_vec (); dump_cand_chains (); } delete alt_base_map; free_affine_expand_cache (&name_expansions); /* Analyze costs and make appropriate replacements. */ analyze_candidates_and_replace (); loop_optimizer_finalize (); delete base_cand_map; base_cand_map = NULL; obstack_free (&chain_obstack, NULL); delete stmt_cand_map; cand_vec.release (); obstack_free (&cand_obstack, NULL); return 0; } } // anon namespace gimple_opt_pass * make_pass_strength_reduction (gcc::context *ctxt) { return new pass_strength_reduction (ctxt); }