CbC/CbC_gcc: gcc/tree-ssa-loop-niter.c comparison

comparison gcc/tree-ssa-loop-niter.c @ 55:77e2b8dfacca gcc-4.4.5

update it from 4.4.3 to 4.5.0

author	ryoma <e075725@ie.u-ryukyu.ac.jp>
date	Fri, 12 Feb 2010 23:39:51 +0900
parents	58ad6c70ea60
children	b7f97abdc517

comparison

equal deleted inserted replaced

-:c156f1bd5cd9
+:77e2b8dfacca
 /* Functions to determine/estimate number of iterations of a loop.
 Copyright (C) 2004, 2005, 2006, 2007, 2008 Free Software Foundation,
 Inc.
 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/>.  */
 #include "config.h"
 if (TREE_CODE (op1) != INTEGER_CST)
 	break;
 *var = op0;
 /* Always sign extend the offset.  */
-off = double_int_sext (tree_to_double_int (op1),
+off = tree_to_double_int (op1);
-			     TYPE_PRECISION (type));
+if (negate)
+	off = double_int_neg (off);
+off = double_int_sext (off, TYPE_PRECISION (type));
 mpz_set_double_int (offset, off, false);
 break;
 case INTEGER_CST:
 *var = build_int_cst_type (type, 0);
 	}
 return;
 default:
 return;
 }
 mpz_init (offc0);
 mpz_init (offc1);
 split_to_var_and_offset (expand_simple_operations (c0), &varc0, offc0);
 split_to_var_and_offset (expand_simple_operations (c1), &varc1, offc1);
 The overflows and underflows may complicate things a bit; each
 overflow decreases the appropriate offset by M, and underflow
 increases it by M.  The above inequality would not necessarily be
 true if
 -- VARX + OFFX underflows and VARX + OFFC0 does not, or
 	VARX + OFFC0 overflows, but VARX + OFFX does not.
 	This may only happen if OFFX < OFFC0.
 -- VARY + OFFY overflows and VARY + OFFC1 does not, or
 	VARY + OFFC1 underflows and VARY + OFFY does not.
 }
 /* Stores the bounds on the value of the expression X - Y in LOOP to BNDS.
 The subtraction is considered to be performed in arbitrary precision,
 without overflows.
 We do not attempt to be too clever regarding the value ranges of X and
 Y; most of the time, they are just integers or ssa names offsetted by
 integer.  However, we try to use the information contained in the
 comparisons before the loop (usually created by loop header copying).  */
 				assumption, build_int_cst (niter_type, 0));
 if (!integer_nonzerop (assumption))
 	niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
 					  niter->assumptions, assumption);
 }
 c = fold_build2 (EXACT_DIV_EXPR, niter_type, c, d);
 tmp = fold_build2 (MULT_EXPR, niter_type, c, inverse (s, bound));
 niter->niter = fold_build2 (BIT_AND_EXPR, niter_type, tmp, bound);
 return true;
 }
 if (integer_zerop (assumption))
 return false;
 if (!integer_nonzerop (assumption))
 niter->assumptions = fold_build2 (TRUTH_AND_EXPR, boolean_type_node,
 				      niter->assumptions, assumption);
 iv0->no_overflow = true;
 iv1->no_overflow = true;
 return true;
 }
 double_int dstep;
 mpz_t mstep, max;
 /* We are going to compute the number of iterations as
 (iv1->base - iv0->base + step - 1) / step, computed in the unsigned
 variant of TYPE.  This formula only works if
 -step + 1 <= (iv1->base - iv0->base) <= MAX - step + 1
 (where MAX is the maximum value of the unsigned variant of TYPE, and
 the computations in this formula are performed in full precision
 (without overflows).
 Usually, for loops with exit condition iv0->base + step * i < iv1->base,
 we have a condition of form iv0->base - step < iv1->base before the loop,
 and for loops iv0->base < iv1->base - step * i the condition
 iv0->base < iv1->base + step, due to loop header copying, which enable us
 to prove the lower bound.
 The upper bound is more complicated.  Unless the expressions for initial
 and final value themselves contain enough information, we usually cannot
 derive it from the context.  */
 /* First check whether the answer does not follow from the bounds we gathered
 mpz_clear (mstep);
 mpz_clear (max);
 if (rolls_p && no_overflow_p)
 return;
 type1 = type;
 if (POINTER_TYPE_P (type))
 type1 = sizetype;
 /* Now the hard part; we must formulate the assumption(s) as expressions, and
 	  assumption = fold_build2 (GE_EXPR, boolean_type_node,
 				    iv0->base, bound);
 	}
 /* And then we can compute iv0->base - diff, and compare it with
 	 iv1->base.  */
 mbzl = fold_build2 (MINUS_EXPR, type1,
 			  fold_convert (type1, iv0->base), diff);
 mbzr = fold_convert (type1, iv1->base);
 }
 else
 {
 /* for (i = iv0->base; i < iv1->base; i++)
 	 or
 	 for (i = iv1->base; i > iv0->base; i--).
 	 In both cases # of iterations is iv1->base - iv0->base, assuming that
 	 iv1->base >= iv0->base.
 First try to derive a lower bound on the value of
 	 iv1->base - iv0->base, computed in full precision.  If the difference
 /* Say that IV0 is the control variable.  Then IV0 <= IV1 iff
 IV0 < IV1 + 1, assuming that IV1 is not equal to the greatest
 value of the type.  This we must know anyway, since if it is
 equal to this value, the loop rolls forever.  We do not check
 this condition for pointer type ivs, as the code cannot rely on
 the object to that the pointer points being placed at the end of
 the address space (and more pragmatically, TYPE_{MIN,MAX}_VALUE is
 not defined for pointers).  */
 if (!exit_must_be_taken && !POINTER_TYPE_P (type))
 ONLY_EXIT is true if we are sure this is the only way the loop could be
 exited (including possibly non-returning function calls, exceptions, etc.)
 -- in this case we can use the information whether the control induction
 variables can overflow or not in a more efficient way.
 The results (number of iterations and assumptions as described in
 comments at struct tree_niter_desc in tree-flow.h) are stored to NITER.
 Returns false if it fails to determine number of iterations, true if it
 was determined (possibly with some assumptions).  */
 {
 niter->niter = build_int_cst (unsigned_type_for (type), 0);
 niter->max = double_int_zero;
 return true;
 }
 /* OK, now we know we have a senseful loop.  Handle several cases, depending
 on what comparison operator is used.  */
 bound_difference (loop, iv1->base, iv0->base, &bnds);
 if (dump_file && (dump_flags & TDF_DETAILS))
 break;
 default:
 return false;
 }
 op0 = gimple_cond_lhs (stmt);
 op1 = gimple_cond_rhs (stmt);
 type = TREE_TYPE (op0);
 if (TREE_CODE (type) != INTEGER_TYPE
 && !POINTER_TYPE_P (type))
 return false;
 if (!simple_iv (loop, loop_containing_stmt (stmt), op0, &iv0, false))
 return false;
 if (!simple_iv (loop, loop_containing_stmt (stmt), op1, &iv1, false))
 return false;
 if (warn)
 {
 const char *wording;
 location_t loc = gimple_location (stmt);
 /* We can provide a more specific warning if one of the operator is
 	 constant and the other advances by +1 or -1.  */
 if (!integer_zerop (iv1.step)
 	  ? (integer_zerop (iv0.step)
 	     && (integer_onep (iv1.step) || integer_all_onesp (iv1.step)))
 wording =
 flag_unsafe_loop_optimizations
 ? N_("assuming that the loop is not infinite")
 : N_("cannot optimize possibly infinite loops");
 else
 	wording =
 	  flag_unsafe_loop_optimizations
 	  ? N_("assuming that the loop counter does not overflow")
 	  : N_("cannot optimize loop, the loop counter may overflow");
-if (LOCATION_LINE (loc) > 0)
+warning_at ((LOCATION_LINE (loc) > 0) ? loc : input_location,
-	warning (OPT_Wunsafe_loop_optimizations, "%H%s", &loc, gettext (wording));
+		  OPT_Wunsafe_loop_optimizations, "%s", gettext (wording));
-else
-	warning (OPT_Wunsafe_loop_optimizations, "%s", gettext (wording));
 }
 return flag_unsafe_loop_optimizations;
 }
 VEC_free (edge, heap, exits);
 return niter ? niter : chrec_dont_know;
 }
+/* Return true if loop is known to have bounded number of iterations.  */
+bool
+finite_loop_p (struct loop *loop)
+{
+unsigned i;
+VEC (edge, heap) *exits;
+edge ex;
+struct tree_niter_desc desc;
+bool finite = false;
+if (flag_unsafe_loop_optimizations)
+return true;
+if ((TREE_READONLY (current_function_decl)
+|| DECL_PURE_P (current_function_decl))
+&& !DECL_LOOPING_CONST_OR_PURE_P (current_function_decl))
+{
+if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "Found loop %i to be finite: it is within pure or const function.\n",
+		 loop->num);
+return true;
+}
+exits = get_loop_exit_edges (loop);
+for (i = 0; VEC_iterate (edge, exits, i, ex); i++)
+{
+if (!just_once_each_iteration_p (loop, ex->src))
+	continue;
+if (number_of_iterations_exit (loop, ex, &desc, false))
+{
+	  if (dump_file && (dump_flags & TDF_DETAILS))
+	    {
+	      fprintf (dump_file, "Found loop %i to be finite: iterating ", loop->num);
+	      print_generic_expr (dump_file, desc.niter, TDF_SLIM);
+	      fprintf (dump_file, " times\n");
+	    }
+	  finite = true;
+	  break;
+	}
+}
+VEC_free (edge, heap, exits);
+return finite;
+}
 /*
 Analysis of a number of iterations of a loop by a brute-force evaluation.
 */
 enum tree_code code;
 if (!bb
 || !flow_bb_inside_loop_p (loop, bb))
 return NULL;
 if (gimple_code (stmt) == GIMPLE_PHI)
 {
 if (bb == loop->header)
 	return stmt;
 if (gimple_code (stmt) != GIMPLE_ASSIGN)
 return NULL;
 code = gimple_assign_rhs_code (stmt);
 if (gimple_references_memory_p (stmt)
-/* Before alias information is computed, operand scanning marks
-	 statements that write memory volatile.  However, the statements
-	 that only read memory are not marked, thus gimple_references_memory_p
-	 returns false for them.  */
 || TREE_CODE_CLASS (code) == tcc_reference
-|| TREE_CODE_CLASS (code) == tcc_declaration
+|| (code == ADDR_EXPR
-|| SINGLE_SSA_DEF_OPERAND (stmt, SSA_OP_DEF) == NULL_DEF_OPERAND_P)
+	  && !is_gimple_min_invariant (gimple_assign_rhs1 (stmt))))
 return NULL;
 use = SINGLE_SSA_TREE_OPERAND (stmt, SSA_OP_USE);
-if (use == NULL_USE_OPERAND_P)
+if (use == NULL_TREE)
 return NULL;
 return chain_of_csts_start (loop, use);
 }
 * the derivation of X consists only from operations with constants
 * the initial value of the phi node is constant
 * the value of the phi node in the next iteration can be derived from the
 value in the current iteration by a chain of operations with constants.
 If such phi node exists, it is returned, otherwise NULL is returned.  */
 static gimple
 get_base_for (struct loop *loop, tree x)
 {
 return NULL;
 return phi;
 }
 /* Given an expression X, then
 * if X is NULL_TREE, we return the constant BASE.
 * otherwise X is a SSA name, whose value in the considered loop is derived
 by a chain of operations with constant from a result of a phi node in
 the header of the loop.  Then we return value of X when the value of the
 result of this phi node is given by the constant BASE.  */
 VEC (edge, heap) *exits = get_loop_exit_edges (loop);
 edge ex;
 tree niter = NULL_TREE, aniter;
 *exit = NULL;
+/* Loops with multiple exits are expensive to handle and less important.  */
+if (!flag_expensive_optimizations
+&& VEC_length (edge, exits) > 1)
+return chrec_dont_know;
 for (i = 0; VEC_iterate (edge, exits, i, ex); i++)
 {
 if (!just_once_each_iteration_p (loop, ex->src))
 	continue;
 }
 /* Returns a constant upper bound on the value of expression VAL.  VAL
 is considered to be unsigned.  If its type is signed, its value must
 be nonnegative.  */
 static double_int
 derive_constant_upper_bound (tree val)
 {
 enum tree_code code;
 tree op0, op1;
 }
 /* Returns a constant upper bound on the value of expression OP0 CODE OP1,
 whose type is TYPE.  The expression is considered to be unsigned.  If
 its type is signed, its value must be nonnegative.  */
 static double_int
 derive_constant_upper_bound_ops (tree type, tree op0,
 				 enum tree_code code, tree op1)
 {
 tree subtype, maxt;
 if (gimple_code (stmt) != GIMPLE_ASSIGN
 	  || gimple_assign_lhs (stmt) != op0)
 	return max;
 return derive_constant_upper_bound_assign (stmt);
 default:
 return max;
 }
 }
 /* Records that every statement in LOOP is executed I_BOUND times.
 /* Returns true if REF is a reference to an array at the end of a dynamically
 allocated structure.  If this is the case, the array may be allocated larger
 than its upper bound implies.  */
-static bool
+bool
 array_at_struct_end_p (tree ref)
 {
 tree base = get_base_address (ref);
 tree parent, field;
 /* Unless the reference is through a pointer, the size of the array matches
 its declaration.  */
 if (!base || !INDIRECT_REF_P (base))
 return false;
 for (;handled_component_p (ref); ref = parent)
 {
 parent = TREE_OPERAND (ref, 0);
 if (TREE_CODE (ref) == COMPONENT_REF)
 || chrec_contains_symbols_defined_in_loop (init, loop->num))
 return true;
 low = array_ref_low_bound (base);
 high = array_ref_up_bound (base);
 /* The case of nonconstant bounds could be handled, but it would be
 complicated.  */
 if (TREE_CODE (low) != INTEGER_CST
 || !high
 || TREE_CODE (high) != INTEGER_CST)
 if (sign)
 next = fold_binary (PLUS_EXPR, type, low, step);
 else
 next = fold_binary (PLUS_EXPR, type, high, step);
 if (tree_int_cst_compare (low, next) <= 0
 && tree_int_cst_compare (next, high) <= 0)
 return true;
 record_nonwrapping_iv (loop, init, step, data->stmt, low, high, true, upper);
 unsigned i;
 basic_block *bbs;
 gimple_stmt_iterator bsi;
 basic_block bb;
 bool reliable;
 bbs = get_loop_body (loop);
 for (i = 0; i < loop->num_nodes; i++)
 {
 bb = bbs[i];
 record_estimate (loop, niter, niter_desc.max,
 		       last_stmt (ex->src),
 		       true, true, true);
 }
 VEC_free (edge, heap, exits);
 infer_loop_bounds_from_undefined (loop);
 /* If we have a measured profile, use it to estimate the number of
 iterations.  */
 if (loop->header->count != 0)
 NITER_BOUND.  If STMT is NULL, we must prove this bound for all
 statements in the loop.  */
 static bool
 n_of_executions_at_most (gimple stmt,
 			 struct nb_iter_bound *niter_bound,
 			 tree niter)
 {
 double_int bound = niter_bound->bound;
 tree nit_type = TREE_TYPE (niter), e;
 enum tree_code cmp;
 if (!double_int_fits_to_tree_p (nit_type, bound))
 return false;
 /* We know that NITER_BOUND->stmt is executed at most NITER_BOUND->bound + 1
 times.  This means that:
 -- if NITER_BOUND->is_exit is true, then everything before
 NITER_BOUND->stmt is executed at most NITER_BOUND->bound + 1
 	times, and everything after it at most NITER_BOUND->bound times.
 -- If NITER_BOUND->is_exit is false, then if we can prove that when STMT
 /* Return false only when the induction variable BASE + STEP * I is
 known to not overflow: i.e. when the number of iterations is small
 enough with respect to the step and initial condition in order to
 keep the evolution confined in TYPEs bounds.  Return true when the
 iv is known to overflow or when the property is not computable.
 USE_OVERFLOW_SEMANTICS is true if this function should assume that
 the rules for overflow of the given language apply (e.g., that signed
 arithmetics in C does not overflow).  */
 bool
 scev_probably_wraps_p (tree base, tree step,
 		       gimple at_stmt, struct loop *loop,
 		       bool use_overflow_semantics)
 {
 struct nb_iter_bound *bound;
 tree delta, step_abs;
 /* FIXME: We really need something like
 http://gcc.gnu.org/ml/gcc-patches/2005-06/msg02025.html.
 We used to test for the following situation that frequently appears
 during address arithmetics:
 D.1621_13 = (long unsigned intD.4) D.1620_12;
 D.1622_14 = D.1621_13 * 8;
 D.1623_15 = (doubleD.29 *) D.1622_14;
 And derived that the sequence corresponding to D_14

Mercurial > hg > CbC > CbC_gcc

comparison gcc/tree-ssa-loop-niter.c @ 55:77e2b8dfacca gcc-4.4.5