CbC/CbC_gcc: gcc/tree-call-cdce.c comparison

comparison gcc/tree-call-cdce.c @ 0:a06113de4d67

first commit

author	kent <kent@cr.ie.u-ryukyu.ac.jp>
date	Fri, 17 Jul 2009 14:47:48 +0900
parents
children	77e2b8dfacca

comparison

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--1:000000000000
+:a06113de4d67
+/* Conditional Dead Call Elimination pass for the GNU compiler.
+Copyright (C) 2008
+Free Software Foundation, Inc.
+Contributed by Xinliang David Li <davidxl@google.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/>.  */
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "ggc.h"
+/* These RTL headers are needed for basic-block.h.  */
+#include "rtl.h"
+#include "tm_p.h"
+#include "hard-reg-set.h"
+#include "obstack.h"
+#include "basic-block.h"
+#include "tree.h"
+#include "diagnostic.h"
+#include "tree-flow.h"
+#include "gimple.h"
+#include "tree-dump.h"
+#include "tree-pass.h"
+#include "timevar.h"
+#include "flags.h"
+/* Conditional dead call elimination
+Some builtin functions can set errno on error conditions, but they
+are otherwise pure.  If the result of a call to such a function is
+not used, the compiler can still not eliminate the call without
+powerful interprocedural analysis to prove that the errno is not
+checked.  However, if the conditions under which the error occurs
+are known, the compiler can conditionally dead code eliminate the
+calls by shrink-wrapping the semi-dead calls into the error condition:
+built_in_call (args)
+==>
+if (error_cond (args))
+built_in_call (args)
+An actual simple example is :
+log (x);   // Mostly dead call
+==>
+if (x < 0)
+log (x);
+With this change, call to log (x) is effectively eliminated, as
+in majority of the cases, log won't be called with x out of
+range.  The branch is totally predictable, so the branch cost
+is low.
+Note that library functions are not supposed to clear errno to zero without
+error.  See IEEE Std 1003.1, section 2.3 Error Numbers, and section 7.5:3 of
+ISO/IEC 9899 (C99).
+The condition wrapping the builtin call is conservatively set to avoid too
+aggressive (wrong) shrink wrapping.  The optimization is called conditional
+dead call elimination because the call is eliminated under the condition
+that the input arguments would not lead to domain or range error (for
+instance when x <= 0 for a log (x) call), however the chances that the error
+condition is hit is very low (those builtin calls which are conditionally
+dead are usually part of the C++ abstraction penalty exposed after
+inlining).  */
+/* A structure for representing input domain of
+a function argument in integer.  If the lower
+bound is -inf, has_lb is set to false.  If the
+upper bound is +inf, has_ub is false.
+is_lb_inclusive and is_ub_inclusive are flags
+to indicate if lb and ub value are inclusive
+respectively.  */
+typedef struct input_domain
+{
+int lb;
+int ub;
+bool has_lb;
+bool has_ub;
+bool is_lb_inclusive;
+bool is_ub_inclusive;
+} inp_domain;
+/* A helper function to construct and return an input
+domain object.  LB is the lower bound, HAS_LB is
+a boolean flag indicating if the lower bound exists,
+and LB_INCLUSIVE is a boolean flag indicating if the
+lower bound is inclusive or not.  UB, HAS_UB, and
+UB_INCLUSIVE have the same meaning, but for upper
+bound of the domain.  */
+static inp_domain
+get_domain (int lb, bool has_lb, bool lb_inclusive,
+int ub, bool has_ub, bool ub_inclusive)
+{
+inp_domain domain;
+domain.lb = lb;
+domain.has_lb = has_lb;
+domain.is_lb_inclusive = lb_inclusive;
+domain.ub = ub;
+domain.has_ub = has_ub;
+domain.is_ub_inclusive = ub_inclusive;
+return domain;
+}
+/* A helper function to check the target format for the
+argument type. In this implementation, only IEEE formats
+are supported.  ARG is the call argument to be checked.
+Returns true if the format is supported.  To support other
+target formats,  function get_no_error_domain needs to be
+enhanced to have range bounds properly computed. Since
+the check is cheap (very small number of candidates
+to be checked), the result is not cached for each float type.  */
+static bool
+check_target_format (tree arg)
+{
+tree type;
+enum machine_mode mode;
+const struct real_format *rfmt;
+type = TREE_TYPE (arg);
+mode = TYPE_MODE (type);
+rfmt = REAL_MODE_FORMAT (mode);
+if ((mode == SFmode
+&& (rfmt == &ieee_single_format || rfmt == &mips_single_format
+	   || rfmt == &motorola_single_format))
+|| (mode == DFmode
+	  && (rfmt == &ieee_double_format || rfmt == &mips_double_format
+	      || rfmt == &motorola_double_format))
+/* For long double, we can not really check XFmode
+which is only defined on intel platforms.
+Candidate pre-selection using builtin function
+code guarantees that we are checking formats
+for long double modes: double, quad, and extended.  */
+|| (mode != SFmode && mode != DFmode
+&& (rfmt == &ieee_quad_format
+	      || rfmt == &mips_quad_format
+	      || rfmt == &ieee_extended_motorola_format
+|| rfmt == &ieee_extended_intel_96_format
+|| rfmt == &ieee_extended_intel_128_format
+|| rfmt == &ieee_extended_intel_96_round_53_format)))
+return true;
+return false;
+}
+/* A helper function to help select calls to pow that are suitable for
+conditional DCE transformation.  It looks for pow calls that can be
+guided with simple conditions.  Such calls either have constant base
+values or base values converted from integers.  Returns true if
+the pow call POW_CALL is a candidate.  */
+/* The maximum integer bit size for base argument of a pow call
+that is suitable for shrink-wrapping transformation.  */
+#define MAX_BASE_INT_BIT_SIZE 32
+static bool
+check_pow (gimple pow_call)
+{
+tree base, expn;
+enum tree_code bc, ec;
+if (gimple_call_num_args (pow_call) != 2)
+return false;
+base = gimple_call_arg (pow_call, 0);
+expn = gimple_call_arg (pow_call, 1);
+if (!check_target_format (expn))
+return false;
+bc = TREE_CODE (base);
+ec = TREE_CODE (expn);
+/* Folding candidates are not interesting.
+Can actually assert that it is already folded.  */
+if (ec == REAL_CST && bc == REAL_CST)
+return false;
+if (bc == REAL_CST)
+{
+/* Only handle a fixed range of constant.  */
+REAL_VALUE_TYPE mv;
+REAL_VALUE_TYPE bcv = TREE_REAL_CST (base);
+if (REAL_VALUES_EQUAL (bcv, dconst1))
+return false;
+if (REAL_VALUES_LESS (bcv, dconst1))
+return false;
+real_from_integer (&mv, TYPE_MODE (TREE_TYPE (base)), 256, 0, 1);
+if (REAL_VALUES_LESS (mv, bcv))
+return false;
+return true;
+}
+else if (bc == SSA_NAME)
+{
+tree base_val0, base_var, type;
+gimple base_def;
+int bit_sz;
+/* Only handles cases where base value is converted
+from integer values.  */
+base_def = SSA_NAME_DEF_STMT (base);
+if (gimple_code (base_def) != GIMPLE_ASSIGN)
+return false;
+if (gimple_assign_rhs_code (base_def) != FLOAT_EXPR)
+return false;
+base_val0 = gimple_assign_rhs1 (base_def);
+base_var = SSA_NAME_VAR (base_val0);
+if (!DECL_P  (base_var))
+return false;
+type = TREE_TYPE (base_var);
+if (TREE_CODE (type) != INTEGER_TYPE)
+return false;
+bit_sz = TYPE_PRECISION (type);
+/* If the type of the base is too wide,
+the resulting shrink wrapping condition
+	 will be too conservative.  */
+if (bit_sz > MAX_BASE_INT_BIT_SIZE)
+return false;
+return true;
+}
+else
+return false;
+}
+/* A helper function to help select candidate function calls that are
+suitable for conditional DCE.  Candidate functions must have single
+valid input domain in this implementation except for pow (see check_pow).
+Returns true if the function call is a candidate.  */
+static bool
+check_builtin_call (gimple bcall)
+{
+tree arg;
+arg = gimple_call_arg (bcall, 0);
+return check_target_format (arg);
+}
+/* A helper function to determine if a builtin function call is a
+candidate for conditional DCE.  Returns true if the builtin call
+is a candidate.  */
+static bool
+is_call_dce_candidate (gimple call)
+{
+tree fn;
+enum built_in_function fnc;
+/* Only potentially dead calls are considered.  */
+if (gimple_call_lhs (call))
+return false;
+fn = gimple_call_fndecl (call);
+if (!fn
+|| !DECL_BUILT_IN (fn)
+|| (DECL_BUILT_IN_CLASS (fn) != BUILT_IN_NORMAL))
+return false;
+fnc = DECL_FUNCTION_CODE (fn);
+switch (fnc)
+{
+/* Trig functions.  */
+CASE_FLT_FN (BUILT_IN_ACOS):
+CASE_FLT_FN (BUILT_IN_ASIN):
+/* Hyperbolic functions.  */
+CASE_FLT_FN (BUILT_IN_ACOSH):
+CASE_FLT_FN (BUILT_IN_ATANH):
+CASE_FLT_FN (BUILT_IN_COSH):
+CASE_FLT_FN (BUILT_IN_SINH):
+/* Log functions.  */
+CASE_FLT_FN (BUILT_IN_LOG):
+CASE_FLT_FN (BUILT_IN_LOG2):
+CASE_FLT_FN (BUILT_IN_LOG10):
+CASE_FLT_FN (BUILT_IN_LOG1P):
+/* Exp functions.  */
+CASE_FLT_FN (BUILT_IN_EXP):
+CASE_FLT_FN (BUILT_IN_EXP2):
+CASE_FLT_FN (BUILT_IN_EXP10):
+CASE_FLT_FN (BUILT_IN_EXPM1):
+CASE_FLT_FN (BUILT_IN_POW10):
+/* Sqrt.  */
+CASE_FLT_FN (BUILT_IN_SQRT):
+return check_builtin_call (call);
+/* Special one: two argument pow.  */
+case BUILT_IN_POW:
+return check_pow (call);
+default:
+break;
+}
+return false;
+}
+/* A helper function to generate gimple statements for
+one bound comparison.  ARG is the call argument to
+be compared with the bound, LBUB is the bound value
+in integer, TCODE is the tree_code of the comparison,
+TEMP_NAME1/TEMP_NAME2 are names of the temporaries,
+CONDS is a vector holding the produced GIMPLE statements,
+and NCONDS points to the variable holding the number
+of logical comparisons.  CONDS is either empty or
+a list ended with a null tree.  */
+static void
+gen_one_condition (tree arg, int lbub,
+enum tree_code tcode,
+const char *temp_name1,
+		   const char *temp_name2,
+VEC (gimple, heap) *conds,
+unsigned *nconds)
+{
+tree lbub_real_cst, lbub_cst, float_type;
+tree temp, tempn, tempc, tempcn;
+gimple stmt1, stmt2, stmt3;
+float_type = TREE_TYPE (arg);
+lbub_cst = build_int_cst (integer_type_node, lbub);
+lbub_real_cst = build_real_from_int_cst (float_type, lbub_cst);
+temp = create_tmp_var (float_type, temp_name1);
+stmt1 = gimple_build_assign (temp, arg);
+tempn = make_ssa_name (temp, stmt1);
+gimple_assign_set_lhs (stmt1, tempn);
+tempc = create_tmp_var (boolean_type_node, temp_name2);
+stmt2 = gimple_build_assign (tempc,
+fold_build2 (tcode,
+					    boolean_type_node,
+					    tempn, lbub_real_cst));
+tempcn = make_ssa_name (tempc, stmt2);
+gimple_assign_set_lhs (stmt2, tempcn);
+stmt3 = gimple_build_cond_from_tree (tempcn, NULL_TREE, NULL_TREE);
+VEC_quick_push (gimple, conds, stmt1);
+VEC_quick_push (gimple, conds, stmt2);
+VEC_quick_push (gimple, conds, stmt3);
+(*nconds)++;
+}
+/* A helper function to generate GIMPLE statements for
+out of input domain check.  ARG is the call argument
+to be runtime checked, DOMAIN holds the valid domain
+for the given function, CONDS points to the vector
+holding the result GIMPLE statements.  *NCONDS is
+the number of logical comparisons.  This function
+produces no more than two logical comparisons, one
+for lower bound check, one for upper bound check.  */
+static void
+gen_conditions_for_domain (tree arg, inp_domain domain,
+VEC (gimple, heap) *conds,
+unsigned *nconds)
+{
+if (domain.has_lb)
+gen_one_condition (arg, domain.lb,
+(domain.is_lb_inclusive
+? LT_EXPR : LE_EXPR),
+"DCE_COND_LB", "DCE_COND_LB_TEST",
+conds, nconds);
+if (domain.has_ub)
+{
+/* Now push a separator.  */
+if (domain.has_lb)
+VEC_quick_push (gimple, conds, NULL);
+gen_one_condition (arg, domain.ub,
+(domain.is_ub_inclusive
+? GT_EXPR : GE_EXPR),
+"DCE_COND_UB", "DCE_COND_UB_TEST",
+conds, nconds);
+}
+}
+/* A helper function to generate condition
+code for the y argument in call pow (some_const, y).
+See candidate selection in check_pow.  Since the
+candidates' base values have a limited range,
+the guarded code generated for y are simple:
+if (y > max_y)
+pow (const, y);
+Note max_y can be computed separately for each
+const base, but in this implementation, we
+choose to compute it using the max base
+in the allowed range for the purpose of
+simplicity.  BASE is the constant base value,
+EXPN is the expression for the exponent argument,
+*CONDS is the vector to hold resulting statements,
+and *NCONDS is the number of logical conditions.  */
+static void
+gen_conditions_for_pow_cst_base (tree base, tree expn,
+VEC (gimple, heap) *conds,
+unsigned *nconds)
+{
+inp_domain exp_domain;
+/* Validate the range of the base constant to make
+sure it is consistent with check_pow.  */
+REAL_VALUE_TYPE mv;
+REAL_VALUE_TYPE bcv = TREE_REAL_CST (base);
+gcc_assert (!REAL_VALUES_EQUAL (bcv, dconst1)
+&& !REAL_VALUES_LESS (bcv, dconst1));
+real_from_integer (&mv, TYPE_MODE (TREE_TYPE (base)), 256, 0, 1);
+gcc_assert (!REAL_VALUES_LESS (mv, bcv));
+exp_domain = get_domain (0, false, false,
+127, true, false);
+gen_conditions_for_domain (expn, exp_domain,
+conds, nconds);
+}
+/* Generate error condition code for pow calls with
+non constant base values.  The candidates selected
+have their base argument value converted from
+integer (see check_pow) value (1, 2, 4 bytes), and
+the max exp value is computed based on the size
+of the integer type (i.e. max possible base value).
+The resulting input domain for exp argument is thus
+conservative (smaller than the max value allowed by
+the runtime value of the base).  BASE is the integer
+base value, EXPN is the expression for the exponent
+argument, *CONDS is the vector to hold resulting
+statements, and *NCONDS is the number of logical
+conditions.  */
+static void
+gen_conditions_for_pow_int_base (tree base, tree expn,
+VEC (gimple, heap) *conds,
+unsigned *nconds)
+{
+gimple base_def;
+tree base_nm, base_val0;
+tree base_var, int_type;
+tree temp, tempn;
+tree cst0;
+gimple stmt1, stmt2;
+int bit_sz, max_exp;
+inp_domain exp_domain;
+base_def = SSA_NAME_DEF_STMT (base);
+base_nm = gimple_assign_lhs (base_def);
+base_val0 = gimple_assign_rhs1 (base_def);
+base_var = SSA_NAME_VAR (base_val0);
+int_type = TREE_TYPE (base_var);
+bit_sz = TYPE_PRECISION (int_type);
+gcc_assert (bit_sz > 0
+&& bit_sz <= MAX_BASE_INT_BIT_SIZE);
+/* Determine the max exp argument value according to
+the size of the base integer.  The max exp value
+is conservatively estimated assuming IEEE754 double
+precision format.  */
+if (bit_sz == 8)
+max_exp = 128;
+else if (bit_sz == 16)
+max_exp = 64;
+else
+{
+gcc_assert (bit_sz == MAX_BASE_INT_BIT_SIZE);
+max_exp = 32;
+}
+/* For pow ((double)x, y), generate the following conditions:
+cond 1:
+temp1 = x;
+if (temp1 <= 0)
+cond 2:
+temp2 = y;
+if (temp2 > max_exp_real_cst)  */
+/* Generate condition in reverse order -- first
+the condition for the exp argument.  */
+exp_domain = get_domain (0, false, false,
+max_exp, true, true);
+gen_conditions_for_domain (expn, exp_domain,
+conds, nconds);
+/* Now generate condition for the base argument.
+Note it does not use the helper function
+gen_conditions_for_domain because the base
+type is integer.  */
+/* Push a separator.  */
+VEC_quick_push (gimple, conds, NULL);
+temp = create_tmp_var (int_type, "DCE_COND1");
+cst0 = build_int_cst (int_type, 0);
+stmt1 = gimple_build_assign (temp, base_val0);
+tempn = make_ssa_name (temp, stmt1);
+gimple_assign_set_lhs (stmt1, tempn);
+stmt2 = gimple_build_cond (LE_EXPR, tempn, cst0, NULL_TREE, NULL_TREE);
+VEC_quick_push (gimple, conds, stmt1);
+VEC_quick_push (gimple, conds, stmt2);
+(*nconds)++;
+}
+/* Method to generate conditional statements for guarding conditionally
+dead calls to pow.  One or more statements can be generated for
+each logical condition.  Statement groups of different conditions
+are separated by a NULL tree and they are stored in the VEC
+conds.  The number of logical conditions are stored in *nconds.
+See C99 standard, 7.12.7.4:2, for description of pow (x, y).
+The precise condition for domain errors are complex.  In this
+implementation, a simplified (but conservative) valid domain
+for x and y are used: x is positive to avoid dom errors, while
+y is smaller than a upper bound (depending on x) to avoid range
+errors.  Runtime code is generated to check x (if not constant)
+and y against the valid domain.  If it is out, jump to the call,
+otherwise the call is bypassed.  POW_CALL is the call statement,
+*CONDS is a vector holding the resulting condition statements,
+and *NCONDS is the number of logical conditions.  */
+static void
+gen_conditions_for_pow (gimple pow_call, VEC (gimple, heap) *conds,
+unsigned *nconds)
+{
+tree base, expn;
+enum tree_code bc, ec;
+#ifdef ENABLE_CHECKING
+gcc_assert (check_pow (pow_call));
+#endif
+*nconds = 0;
+base = gimple_call_arg (pow_call, 0);
+expn = gimple_call_arg (pow_call, 1);
+bc = TREE_CODE (base);
+ec = TREE_CODE (expn);
+if (bc == REAL_CST)
+gen_conditions_for_pow_cst_base (base, expn, conds, nconds);
+else if (bc == SSA_NAME)
+gen_conditions_for_pow_int_base (base, expn, conds, nconds);
+else
+gcc_unreachable ();
+}
+/* A helper routine to help computing the valid input domain
+for a builtin function.  See C99 7.12.7 for details.  In this
+implementation, we only handle single region domain.  The
+resulting region can be conservative (smaller) than the actual
+one and rounded to integers.  Some of the bounds are documented
+in the standard, while other limit constants are computed
+assuming IEEE floating point format (for SF and DF modes).
+Since IEEE only sets minimum requirements for long double format,
+different long double formats exist under different implementations
+(e.g, 64 bit double precision (DF), 80 bit double-extended
+precision (XF), and 128 bit quad precision (QF) ).  For simplicity,
+in this implementation, the computed bounds for long double assume
+64 bit format (DF), and are therefore conservative.  Another
+assumption is that single precision float type is always SF mode,
+and double type is DF mode.  This function is quite
+implementation specific, so it may not be suitable to be part of
+builtins.c.  This needs to be revisited later to see if it can
+be leveraged in x87 assembly expansion.  */
+static inp_domain
+get_no_error_domain (enum built_in_function fnc)
+{
+switch (fnc)
+{
+/* Trig functions: return [-1, +1]  */
+CASE_FLT_FN (BUILT_IN_ACOS):
+CASE_FLT_FN (BUILT_IN_ASIN):
+return get_domain (-1, true, true,
+1, true, true);
+/* Hyperbolic functions.  */
+CASE_FLT_FN (BUILT_IN_ACOSH):
+/* acosh: [1, +inf)  */
+return get_domain (1, true, true,
+1, false, false);
+CASE_FLT_FN (BUILT_IN_ATANH):
+/* atanh: (-1, +1)  */
+return get_domain (-1, true, false,
+1, true, false);
+case BUILT_IN_COSHF:
+case BUILT_IN_SINHF:
+/* coshf: (-89, +89)  */
+return get_domain (-89, true, false,
+89, true, false);
+case BUILT_IN_COSH:
+case BUILT_IN_SINH:
+case BUILT_IN_COSHL:
+case BUILT_IN_SINHL:
+/* cosh: (-710, +710)  */
+return get_domain (-710, true, false,
+710, true, false);
+/* Log functions: (0, +inf)  */
+CASE_FLT_FN (BUILT_IN_LOG):
+CASE_FLT_FN (BUILT_IN_LOG2):
+CASE_FLT_FN (BUILT_IN_LOG10):
+return get_domain (0, true, false,
+0, false, false);
+CASE_FLT_FN (BUILT_IN_LOG1P):
+return get_domain (-1, true, false,
+0, false, false);
+/* Exp functions.  */
+case BUILT_IN_EXPF:
+case BUILT_IN_EXPM1F:
+/* expf: (-inf, 88)  */
+return get_domain (-1, false, false,
+88, true, false);
+case BUILT_IN_EXP:
+case BUILT_IN_EXPM1:
+case BUILT_IN_EXPL:
+case BUILT_IN_EXPM1L:
+/* exp: (-inf, 709)  */
+return get_domain (-1, false, false,
+709, true, false);
+case BUILT_IN_EXP2F:
+/* exp2f: (-inf, 128)  */
+return get_domain (-1, false, false,
+128, true, false);
+case BUILT_IN_EXP2:
+case BUILT_IN_EXP2L:
+/* exp2: (-inf, 1024)  */
+return get_domain (-1, false, false,
+1024, true, false);
+case BUILT_IN_EXP10F:
+case BUILT_IN_POW10F:
+/* exp10f: (-inf, 38)  */
+return get_domain (-1, false, false,
+38, true, false);
+case BUILT_IN_EXP10:
+case BUILT_IN_POW10:
+case BUILT_IN_EXP10L:
+case BUILT_IN_POW10L:
+/* exp10: (-inf, 308)  */
+return get_domain (-1, false, false,
+308, true, false);
+/* sqrt: [0, +inf)  */
+CASE_FLT_FN (BUILT_IN_SQRT):
+return get_domain (0, true, true,
+0, false, false);
+default:
+gcc_unreachable ();
+}
+gcc_unreachable ();
+}
+/* The function to generate shrink wrap conditions for a partially
+dead builtin call whose return value is not used anywhere,
+but has to be kept live due to potential error condition.
+BI_CALL is the builtin call, CONDS is the vector of statements
+for condition code, NCODES is the pointer to the number of
+logical conditions.  Statements belonging to different logical
+condition are separated by NULL tree in the vector.  */
+static void
+gen_shrink_wrap_conditions (gimple bi_call, VEC (gimple, heap) *conds,
+unsigned int *nconds)
+{
+gimple call;
+tree fn;
+enum built_in_function fnc;
+gcc_assert (nconds && conds);
+gcc_assert (VEC_length (gimple, conds) == 0);
+gcc_assert (is_gimple_call (bi_call));
+call = bi_call;
+fn = gimple_call_fndecl (call);
+gcc_assert (fn && DECL_BUILT_IN (fn));
+fnc = DECL_FUNCTION_CODE (fn);
+*nconds = 0;
+if (fnc == BUILT_IN_POW)
+gen_conditions_for_pow (call, conds, nconds);
+else
+{
+tree arg;
+inp_domain domain = get_no_error_domain (fnc);
+*nconds = 0;
+arg = gimple_call_arg (bi_call, 0);
+gen_conditions_for_domain (arg, domain, conds, nconds);
+}
+return;
+}
+/* Probability of the branch (to the call) is taken.  */
+#define ERR_PROB 0.01
+/* The function to shrink wrap a partially dead builtin call
+whose return value is not used anywhere, but has to be kept
+live due to potential error condition.  Returns true if the
+transformation actually happens.  */
+static bool
+shrink_wrap_one_built_in_call (gimple bi_call)
+{
+gimple_stmt_iterator bi_call_bsi;
+basic_block bi_call_bb, join_tgt_bb, guard_bb, guard_bb0;
+edge join_tgt_in_edge_from_call, join_tgt_in_edge_fall_thru;
+edge bi_call_in_edge0, guard_bb_in_edge;
+VEC (gimple, heap) *conds;
+unsigned tn_cond_stmts, nconds;
+unsigned ci;
+gimple cond_expr = NULL;
+gimple cond_expr_start;
+tree bi_call_label_decl;
+gimple bi_call_label;
+conds = VEC_alloc (gimple, heap, 12);
+gen_shrink_wrap_conditions (bi_call, conds, &nconds);
+/* This can happen if the condition generator decides
+it is not beneficial to do the transformation.  Just
+return false and do not do any transformation for
+the call.  */
+if (nconds == 0)
+return false;
+bi_call_bb = gimple_bb (bi_call);
+/* Now find the join target bb -- split
+bi_call_bb if needed.  */
+bi_call_bsi = gsi_for_stmt (bi_call);
+join_tgt_in_edge_from_call = split_block (bi_call_bb, bi_call);
+bi_call_bsi = gsi_for_stmt (bi_call);
+join_tgt_bb = join_tgt_in_edge_from_call->dest;
+/* Now it is time to insert the first conditional expression
+into bi_call_bb and split this bb so that bi_call is
+shrink-wrapped.  */
+tn_cond_stmts = VEC_length (gimple, conds);
+cond_expr = NULL;
+cond_expr_start = VEC_index (gimple, conds, 0);
+for (ci = 0; ci < tn_cond_stmts; ci++)
+{
+gimple c = VEC_index (gimple, conds, ci);
+gcc_assert (c || ci != 0);
+if (!c)
+break;
+gsi_insert_before (&bi_call_bsi, c, GSI_SAME_STMT);
+cond_expr = c;
+}
+nconds--;
+ci++;
+gcc_assert (cond_expr && gimple_code (cond_expr) == GIMPLE_COND);
+/* Now the label.  */
+bi_call_label_decl = create_artificial_label ();
+bi_call_label = gimple_build_label (bi_call_label_decl);
+gsi_insert_before (&bi_call_bsi, bi_call_label, GSI_SAME_STMT);
+bi_call_in_edge0 = split_block (bi_call_bb, cond_expr);
+bi_call_in_edge0->flags &= ~EDGE_FALLTHRU;
+bi_call_in_edge0->flags |= EDGE_TRUE_VALUE;
+guard_bb0 = bi_call_bb;
+bi_call_bb = bi_call_in_edge0->dest;
+join_tgt_in_edge_fall_thru = make_edge (guard_bb0, join_tgt_bb,
+EDGE_FALSE_VALUE);
+bi_call_in_edge0->probability = REG_BR_PROB_BASE * ERR_PROB;
+join_tgt_in_edge_fall_thru->probability =
+REG_BR_PROB_BASE - bi_call_in_edge0->probability;
+/* Code generation for the rest of the conditions  */
+guard_bb = guard_bb0;
+while (nconds > 0)
+{
+unsigned ci0;
+edge bi_call_in_edge;
+gimple_stmt_iterator guard_bsi = gsi_for_stmt (cond_expr_start);
+ci0 = ci;
+cond_expr_start = VEC_index (gimple, conds, ci0);
+for (; ci < tn_cond_stmts; ci++)
+{
+gimple c = VEC_index (gimple, conds, ci);
+gcc_assert (c || ci != ci0);
+if (!c)
+break;
+gsi_insert_before (&guard_bsi, c, GSI_SAME_STMT);
+cond_expr = c;
+}
+nconds--;
+ci++;
+gcc_assert (cond_expr && gimple_code (cond_expr) == GIMPLE_COND);
+guard_bb_in_edge = split_block (guard_bb, cond_expr);
+guard_bb_in_edge->flags &= ~EDGE_FALLTHRU;
+guard_bb_in_edge->flags |= EDGE_FALSE_VALUE;
+bi_call_in_edge = make_edge (guard_bb, bi_call_bb, EDGE_TRUE_VALUE);
+bi_call_in_edge->probability = REG_BR_PROB_BASE * ERR_PROB;
+guard_bb_in_edge->probability =
+REG_BR_PROB_BASE - bi_call_in_edge->probability;
+}
+VEC_free (gimple, heap, conds);
+if (dump_file && (dump_flags & TDF_DETAILS))
+{
+location_t loc;
+loc = gimple_location (bi_call);
+fprintf (dump_file,
+"%s:%d: note: function call is shrink-wrapped"
+" into error conditions.\n",
+LOCATION_FILE (loc), LOCATION_LINE (loc));
+}
+return true;
+}
+/* The top level function for conditional dead code shrink
+wrapping transformation.  */
+static bool
+shrink_wrap_conditional_dead_built_in_calls (VEC (gimple, heap) *calls)
+{
+bool changed = false;
+unsigned i = 0;
+unsigned n = VEC_length (gimple, calls);
+if (n == 0)
+return false;
+for (; i < n ; i++)
+{
+gimple bi_call = VEC_index (gimple, calls, i);
+changed |= shrink_wrap_one_built_in_call (bi_call);
+}
+return changed;
+}
+/* Pass entry points.  */
+static unsigned int
+tree_call_cdce (void)
+{
+basic_block bb;
+gimple_stmt_iterator i;
+bool something_changed = false;
+VEC (gimple, heap) *cond_dead_built_in_calls = NULL;
+FOR_EACH_BB (bb)
+{
+/* Collect dead call candidates.  */
+for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
+{
+	  gimple stmt = gsi_stmt (i);
+if (is_gimple_call (stmt)
+&& is_call_dce_candidate (stmt))
+{
+if (dump_file && (dump_flags & TDF_DETAILS))
+{
+fprintf (dump_file, "Found conditional dead call: ");
+print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
+fprintf (dump_file, "\n");
+}
+	      if (cond_dead_built_in_calls == NULL)
+		cond_dead_built_in_calls = VEC_alloc (gimple, heap, 64);
+	      VEC_safe_push (gimple, heap, cond_dead_built_in_calls, stmt);
+}
+	}
+}
+if (cond_dead_built_in_calls == NULL)
+return 0;
+something_changed
+= shrink_wrap_conditional_dead_built_in_calls (cond_dead_built_in_calls);
+VEC_free (gimple, heap, cond_dead_built_in_calls);
+if (something_changed)
+{
+free_dominance_info (CDI_DOMINATORS);
+free_dominance_info (CDI_POST_DOMINATORS);
+return (TODO_update_ssa | TODO_cleanup_cfg | TODO_ggc_collect
+| TODO_remove_unused_locals);
+}
+else
+return 0;
+}
+static bool
+gate_call_cdce (void)
+{
+/* The limit constants used in the implementation
+assume IEEE floating point format.  Other formats
+can be supported in the future if needed.  */
+return flag_tree_builtin_call_dce != 0 && optimize_function_for_speed_p (cfun);
+}
+struct gimple_opt_pass pass_call_cdce =
+{
+{
+GIMPLE_PASS,
+"cdce",                               /* name */
+gate_call_cdce,                       /* gate */
+tree_call_cdce,                       /* execute */
+NULL,                                 /* sub */
+NULL,                                 /* next */
+0,                                    /* static_pass_number */
+TV_TREE_CALL_CDCE,                    /* tv_id */
+PROP_cfg | PROP_ssa,                  /* properties_required */
+0,                                    /* properties_provided */
+0,                                    /* properties_destroyed */
+0,                                    /* todo_flags_start */
+TODO_dump_func | TODO_verify_ssa      /* todo_flags_finish */
+}
+};

Mercurial > hg > CbC > CbC_gcc

comparison gcc/tree-call-cdce.c @ 0:a06113de4d67