966 lines
30 KiB
C
966 lines
30 KiB
C
/* Conditional Dead Call Elimination pass for the GNU compiler.
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Copyright (C) 2008-2014 Free Software Foundation, Inc.
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Contributed by Xinliang David Li <davidxl@google.com>
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 3, or (at your option) any
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later version.
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GCC is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#include "config.h"
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#include "system.h"
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#include "coretypes.h"
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#include "tm.h"
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#include "basic-block.h"
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#include "tree.h"
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#include "stor-layout.h"
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#include "gimple-pretty-print.h"
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#include "tree-ssa-alias.h"
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#include "internal-fn.h"
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#include "gimple-expr.h"
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#include "is-a.h"
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#include "gimple.h"
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#include "gimple-iterator.h"
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#include "gimple-ssa.h"
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#include "tree-cfg.h"
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#include "stringpool.h"
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#include "tree-ssanames.h"
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#include "tree-into-ssa.h"
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#include "tree-pass.h"
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#include "flags.h"
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/* Conditional dead call elimination
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Some builtin functions can set errno on error conditions, but they
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are otherwise pure. If the result of a call to such a function is
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not used, the compiler can still not eliminate the call without
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powerful interprocedural analysis to prove that the errno is not
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checked. However, if the conditions under which the error occurs
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are known, the compiler can conditionally dead code eliminate the
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calls by shrink-wrapping the semi-dead calls into the error condition:
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built_in_call (args)
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==>
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if (error_cond (args))
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built_in_call (args)
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An actual simple example is :
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log (x); // Mostly dead call
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==>
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if (x < 0)
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log (x);
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With this change, call to log (x) is effectively eliminated, as
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in majority of the cases, log won't be called with x out of
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range. The branch is totally predictable, so the branch cost
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is low.
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Note that library functions are not supposed to clear errno to zero without
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error. See IEEE Std 1003.1, section 2.3 Error Numbers, and section 7.5:3 of
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ISO/IEC 9899 (C99).
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The condition wrapping the builtin call is conservatively set to avoid too
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aggressive (wrong) shrink wrapping. The optimization is called conditional
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dead call elimination because the call is eliminated under the condition
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that the input arguments would not lead to domain or range error (for
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instance when x <= 0 for a log (x) call), however the chances that the error
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condition is hit is very low (those builtin calls which are conditionally
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dead are usually part of the C++ abstraction penalty exposed after
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inlining). */
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/* A structure for representing input domain of
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a function argument in integer. If the lower
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bound is -inf, has_lb is set to false. If the
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upper bound is +inf, has_ub is false.
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is_lb_inclusive and is_ub_inclusive are flags
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to indicate if lb and ub value are inclusive
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respectively. */
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typedef struct input_domain
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{
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int lb;
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int ub;
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bool has_lb;
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bool has_ub;
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bool is_lb_inclusive;
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bool is_ub_inclusive;
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} inp_domain;
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/* A helper function to construct and return an input
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domain object. LB is the lower bound, HAS_LB is
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a boolean flag indicating if the lower bound exists,
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and LB_INCLUSIVE is a boolean flag indicating if the
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lower bound is inclusive or not. UB, HAS_UB, and
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UB_INCLUSIVE have the same meaning, but for upper
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bound of the domain. */
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static inp_domain
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get_domain (int lb, bool has_lb, bool lb_inclusive,
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int ub, bool has_ub, bool ub_inclusive)
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{
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inp_domain domain;
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domain.lb = lb;
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domain.has_lb = has_lb;
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domain.is_lb_inclusive = lb_inclusive;
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domain.ub = ub;
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domain.has_ub = has_ub;
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domain.is_ub_inclusive = ub_inclusive;
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return domain;
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}
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/* A helper function to check the target format for the
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argument type. In this implementation, only IEEE formats
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are supported. ARG is the call argument to be checked.
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Returns true if the format is supported. To support other
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target formats, function get_no_error_domain needs to be
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enhanced to have range bounds properly computed. Since
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the check is cheap (very small number of candidates
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to be checked), the result is not cached for each float type. */
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static bool
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check_target_format (tree arg)
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{
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tree type;
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enum machine_mode mode;
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const struct real_format *rfmt;
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type = TREE_TYPE (arg);
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mode = TYPE_MODE (type);
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rfmt = REAL_MODE_FORMAT (mode);
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if ((mode == SFmode
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&& (rfmt == &ieee_single_format || rfmt == &mips_single_format
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|| rfmt == &motorola_single_format))
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|| (mode == DFmode
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&& (rfmt == &ieee_double_format || rfmt == &mips_double_format
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|| rfmt == &motorola_double_format))
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/* For long double, we can not really check XFmode
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which is only defined on intel platforms.
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Candidate pre-selection using builtin function
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code guarantees that we are checking formats
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for long double modes: double, quad, and extended. */
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|| (mode != SFmode && mode != DFmode
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&& (rfmt == &ieee_quad_format
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|| rfmt == &mips_quad_format
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|| rfmt == &ieee_extended_motorola_format
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|| rfmt == &ieee_extended_intel_96_format
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|| rfmt == &ieee_extended_intel_128_format
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|| rfmt == &ieee_extended_intel_96_round_53_format)))
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return true;
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return false;
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}
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/* A helper function to help select calls to pow that are suitable for
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conditional DCE transformation. It looks for pow calls that can be
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guided with simple conditions. Such calls either have constant base
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values or base values converted from integers. Returns true if
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the pow call POW_CALL is a candidate. */
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/* The maximum integer bit size for base argument of a pow call
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that is suitable for shrink-wrapping transformation. */
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#define MAX_BASE_INT_BIT_SIZE 32
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static bool
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check_pow (gimple pow_call)
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{
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tree base, expn;
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enum tree_code bc, ec;
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if (gimple_call_num_args (pow_call) != 2)
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return false;
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base = gimple_call_arg (pow_call, 0);
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expn = gimple_call_arg (pow_call, 1);
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if (!check_target_format (expn))
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return false;
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bc = TREE_CODE (base);
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ec = TREE_CODE (expn);
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/* Folding candidates are not interesting.
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Can actually assert that it is already folded. */
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if (ec == REAL_CST && bc == REAL_CST)
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return false;
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if (bc == REAL_CST)
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{
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/* Only handle a fixed range of constant. */
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REAL_VALUE_TYPE mv;
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REAL_VALUE_TYPE bcv = TREE_REAL_CST (base);
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if (REAL_VALUES_EQUAL (bcv, dconst1))
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return false;
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if (REAL_VALUES_LESS (bcv, dconst1))
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return false;
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real_from_integer (&mv, TYPE_MODE (TREE_TYPE (base)), 256, 0, 1);
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if (REAL_VALUES_LESS (mv, bcv))
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return false;
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return true;
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}
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else if (bc == SSA_NAME)
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{
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tree base_val0, type;
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gimple base_def;
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int bit_sz;
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/* Only handles cases where base value is converted
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from integer values. */
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base_def = SSA_NAME_DEF_STMT (base);
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if (gimple_code (base_def) != GIMPLE_ASSIGN)
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return false;
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if (gimple_assign_rhs_code (base_def) != FLOAT_EXPR)
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return false;
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base_val0 = gimple_assign_rhs1 (base_def);
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type = TREE_TYPE (base_val0);
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if (TREE_CODE (type) != INTEGER_TYPE)
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return false;
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bit_sz = TYPE_PRECISION (type);
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/* If the type of the base is too wide,
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the resulting shrink wrapping condition
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will be too conservative. */
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if (bit_sz > MAX_BASE_INT_BIT_SIZE)
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return false;
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return true;
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}
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else
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return false;
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}
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/* A helper function to help select candidate function calls that are
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suitable for conditional DCE. Candidate functions must have single
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valid input domain in this implementation except for pow (see check_pow).
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Returns true if the function call is a candidate. */
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static bool
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check_builtin_call (gimple bcall)
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{
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tree arg;
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arg = gimple_call_arg (bcall, 0);
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return check_target_format (arg);
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}
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/* A helper function to determine if a builtin function call is a
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candidate for conditional DCE. Returns true if the builtin call
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is a candidate. */
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static bool
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is_call_dce_candidate (gimple call)
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{
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tree fn;
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enum built_in_function fnc;
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/* Only potentially dead calls are considered. */
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if (gimple_call_lhs (call))
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return false;
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fn = gimple_call_fndecl (call);
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if (!fn
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|| !DECL_BUILT_IN (fn)
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|| (DECL_BUILT_IN_CLASS (fn) != BUILT_IN_NORMAL))
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return false;
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fnc = DECL_FUNCTION_CODE (fn);
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switch (fnc)
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{
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/* Trig functions. */
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CASE_FLT_FN (BUILT_IN_ACOS):
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CASE_FLT_FN (BUILT_IN_ASIN):
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/* Hyperbolic functions. */
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CASE_FLT_FN (BUILT_IN_ACOSH):
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CASE_FLT_FN (BUILT_IN_ATANH):
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CASE_FLT_FN (BUILT_IN_COSH):
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CASE_FLT_FN (BUILT_IN_SINH):
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/* Log functions. */
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CASE_FLT_FN (BUILT_IN_LOG):
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CASE_FLT_FN (BUILT_IN_LOG2):
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CASE_FLT_FN (BUILT_IN_LOG10):
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CASE_FLT_FN (BUILT_IN_LOG1P):
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/* Exp functions. */
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CASE_FLT_FN (BUILT_IN_EXP):
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CASE_FLT_FN (BUILT_IN_EXP2):
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CASE_FLT_FN (BUILT_IN_EXP10):
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CASE_FLT_FN (BUILT_IN_EXPM1):
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CASE_FLT_FN (BUILT_IN_POW10):
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/* Sqrt. */
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CASE_FLT_FN (BUILT_IN_SQRT):
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return check_builtin_call (call);
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/* Special one: two argument pow. */
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case BUILT_IN_POW:
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return check_pow (call);
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default:
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break;
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}
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return false;
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}
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/* A helper function to generate gimple statements for
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one bound comparison. ARG is the call argument to
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be compared with the bound, LBUB is the bound value
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in integer, TCODE is the tree_code of the comparison,
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TEMP_NAME1/TEMP_NAME2 are names of the temporaries,
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CONDS is a vector holding the produced GIMPLE statements,
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and NCONDS points to the variable holding the number
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of logical comparisons. CONDS is either empty or
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a list ended with a null tree. */
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static void
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gen_one_condition (tree arg, int lbub,
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enum tree_code tcode,
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const char *temp_name1,
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const char *temp_name2,
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vec<gimple> conds,
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unsigned *nconds)
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{
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tree lbub_real_cst, lbub_cst, float_type;
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tree temp, tempn, tempc, tempcn;
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gimple stmt1, stmt2, stmt3;
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float_type = TREE_TYPE (arg);
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lbub_cst = build_int_cst (integer_type_node, lbub);
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lbub_real_cst = build_real_from_int_cst (float_type, lbub_cst);
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||
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temp = create_tmp_var (float_type, temp_name1);
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stmt1 = gimple_build_assign (temp, arg);
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tempn = make_ssa_name (temp, stmt1);
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gimple_assign_set_lhs (stmt1, tempn);
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||
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tempc = create_tmp_var (boolean_type_node, temp_name2);
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stmt2 = gimple_build_assign (tempc,
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fold_build2 (tcode,
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boolean_type_node,
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tempn, lbub_real_cst));
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tempcn = make_ssa_name (tempc, stmt2);
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gimple_assign_set_lhs (stmt2, tempcn);
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||
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stmt3 = gimple_build_cond_from_tree (tempcn, NULL_TREE, NULL_TREE);
|
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conds.quick_push (stmt1);
|
||
conds.quick_push (stmt2);
|
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conds.quick_push (stmt3);
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(*nconds)++;
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||
}
|
||
|
||
/* A helper function to generate GIMPLE statements for
|
||
out of input domain check. ARG is the call argument
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||
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,
|
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vec<gimple> conds,
|
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unsigned *nconds)
|
||
{
|
||
if (domain.has_lb)
|
||
gen_one_condition (arg, domain.lb,
|
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(domain.is_lb_inclusive
|
||
? LT_EXPR : LE_EXPR),
|
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"DCE_COND_LB", "DCE_COND_LB_TEST",
|
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conds, nconds);
|
||
|
||
if (domain.has_ub)
|
||
{
|
||
/* Now push a separator. */
|
||
if (domain.has_lb)
|
||
conds.quick_push (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> 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> conds,
|
||
unsigned *nconds)
|
||
{
|
||
gimple base_def;
|
||
tree base_val0;
|
||
tree 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_val0 = gimple_assign_rhs1 (base_def);
|
||
int_type = TREE_TYPE (base_val0);
|
||
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. */
|
||
conds.quick_push (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);
|
||
|
||
conds.quick_push (stmt1);
|
||
conds.quick_push (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> conds,
|
||
unsigned *nconds)
|
||
{
|
||
tree base, expn;
|
||
enum tree_code bc;
|
||
|
||
gcc_checking_assert (check_pow (pow_call));
|
||
|
||
*nconds = 0;
|
||
|
||
base = gimple_call_arg (pow_call, 0);
|
||
expn = gimple_call_arg (pow_call, 1);
|
||
|
||
bc = TREE_CODE (base);
|
||
|
||
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> conds,
|
||
unsigned int *nconds)
|
||
{
|
||
gimple call;
|
||
tree fn;
|
||
enum built_in_function fnc;
|
||
|
||
gcc_assert (nconds && conds.exists ());
|
||
gcc_assert (conds.length () == 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;
|
||
unsigned tn_cond_stmts, nconds;
|
||
unsigned ci;
|
||
gimple cond_expr = NULL;
|
||
gimple cond_expr_start;
|
||
tree bi_call_label_decl;
|
||
gimple bi_call_label;
|
||
|
||
auto_vec<gimple, 12> conds;
|
||
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. */
|
||
if (stmt_ends_bb_p (bi_call))
|
||
{
|
||
/* If the call must be the last in the bb, don't split the block,
|
||
it could e.g. have EH edges. */
|
||
join_tgt_in_edge_from_call = find_fallthru_edge (bi_call_bb->succs);
|
||
if (join_tgt_in_edge_from_call == NULL)
|
||
return false;
|
||
}
|
||
else
|
||
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 = conds.length ();
|
||
cond_expr = NULL;
|
||
cond_expr_start = conds[0];
|
||
for (ci = 0; ci < tn_cond_stmts; ci++)
|
||
{
|
||
gimple c = 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 (gimple_location (bi_call));
|
||
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;
|
||
bi_call_in_edge0->count =
|
||
apply_probability (guard_bb0->count,
|
||
bi_call_in_edge0->probability);
|
||
join_tgt_in_edge_fall_thru->probability =
|
||
inverse_probability (bi_call_in_edge0->probability);
|
||
join_tgt_in_edge_fall_thru->count =
|
||
guard_bb0->count - bi_call_in_edge0->count;
|
||
|
||
/* 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 = conds[ci0];
|
||
for (; ci < tn_cond_stmts; ci++)
|
||
{
|
||
gimple c = 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;
|
||
bi_call_in_edge->count =
|
||
apply_probability (guard_bb->count,
|
||
bi_call_in_edge->probability);
|
||
guard_bb_in_edge->probability =
|
||
inverse_probability (bi_call_in_edge->probability);
|
||
guard_bb_in_edge->count = guard_bb->count - bi_call_in_edge->count;
|
||
}
|
||
|
||
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> calls)
|
||
{
|
||
bool changed = false;
|
||
unsigned i = 0;
|
||
|
||
unsigned n = calls.length ();
|
||
if (n == 0)
|
||
return false;
|
||
|
||
for (; i < n ; i++)
|
||
{
|
||
gimple bi_call = 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;
|
||
auto_vec<gimple> cond_dead_built_in_calls;
|
||
FOR_EACH_BB_FN (bb, cfun)
|
||
{
|
||
/* 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.exists ())
|
||
cond_dead_built_in_calls.create (64);
|
||
cond_dead_built_in_calls.safe_push (stmt);
|
||
}
|
||
}
|
||
}
|
||
|
||
if (!cond_dead_built_in_calls.exists ())
|
||
return 0;
|
||
|
||
something_changed
|
||
= shrink_wrap_conditional_dead_built_in_calls (cond_dead_built_in_calls);
|
||
|
||
if (something_changed)
|
||
{
|
||
free_dominance_info (CDI_DOMINATORS);
|
||
free_dominance_info (CDI_POST_DOMINATORS);
|
||
/* As we introduced new control-flow we need to insert PHI-nodes
|
||
for the call-clobbers of the remaining call. */
|
||
mark_virtual_operands_for_renaming (cfun);
|
||
return TODO_update_ssa;
|
||
}
|
||
|
||
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);
|
||
}
|
||
|
||
namespace {
|
||
|
||
const pass_data pass_data_call_cdce =
|
||
{
|
||
GIMPLE_PASS, /* type */
|
||
"cdce", /* name */
|
||
OPTGROUP_NONE, /* optinfo_flags */
|
||
true, /* has_gate */
|
||
true, /* has_execute */
|
||
TV_TREE_CALL_CDCE, /* tv_id */
|
||
( PROP_cfg | PROP_ssa ), /* properties_required */
|
||
0, /* properties_provided */
|
||
0, /* properties_destroyed */
|
||
0, /* todo_flags_start */
|
||
TODO_verify_ssa, /* todo_flags_finish */
|
||
};
|
||
|
||
class pass_call_cdce : public gimple_opt_pass
|
||
{
|
||
public:
|
||
pass_call_cdce (gcc::context *ctxt)
|
||
: gimple_opt_pass (pass_data_call_cdce, ctxt)
|
||
{}
|
||
|
||
/* opt_pass methods: */
|
||
bool gate () { return gate_call_cdce (); }
|
||
unsigned int execute () { return tree_call_cdce (); }
|
||
|
||
}; // class pass_call_cdce
|
||
|
||
} // anon namespace
|
||
|
||
gimple_opt_pass *
|
||
make_pass_call_cdce (gcc::context *ctxt)
|
||
{
|
||
return new pass_call_cdce (ctxt);
|
||
}
|