From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1666) id DA1763AA9400; Mon, 12 Dec 2022 11:20:57 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org DA1763AA9400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1670844057; bh=aK7lTKT+VnmeXnSDa2KZXbBHN6jfObzzlt1S9VFImH0=; h=From:To:Subject:Date:From; b=bqegT+dw+op2a6zD5ibAA7/IwGDeZJM7Ebe0o9Cmm+O/lbvmnSETB9YcxjU4keqs2 VWkEjT43W9XAlm8Ko0h35ew1/qrtlge7o90259SQyQNN7rE/w582Z5xiIysAqIy+Hz ncJk91tFGe+8vdVPywJRHc/nP3n1DnnZI+93Gz1g= MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Richard Biener To: gcc-cvs@gcc.gnu.org Subject: [gcc r12-8977] tree-optimization/107833 - invariant motion of uninit uses X-Act-Checkin: gcc X-Git-Author: Richard Biener X-Git-Refname: refs/heads/releases/gcc-12 X-Git-Oldrev: 232305bd0c8dd37b17b815864e730aa630714606 X-Git-Newrev: 812847a9d12c0b65695cbe1a23959b69a7e62355 Message-Id: <20221212112057.DA1763AA9400@sourceware.org> Date: Mon, 12 Dec 2022 11:20:57 +0000 (GMT) List-Id: https://gcc.gnu.org/g:812847a9d12c0b65695cbe1a23959b69a7e62355 commit r12-8977-g812847a9d12c0b65695cbe1a23959b69a7e62355 Author: Richard Biener Date: Fri Dec 2 14:52:20 2022 +0100 tree-optimization/107833 - invariant motion of uninit uses The following fixes a wrong-code bug caused by loop invariant motion hoisting an expression using an uninitialized value outside of its controlling condition causing IVOPTs to use that to rewrite a defined value. PR107839 is a similar case involving a bogus uninit diagnostic. PR tree-optimization/107833 PR tree-optimization/107839 * cfghooks.cc: Include tree.h. * tree-ssa-loop-im.cc (movement_possibility): Wrap and make stmts using any ssa_name_maybe_undef_p operand to preserve execution. (loop_invariant_motion_in_fun): Call mark_ssa_maybe_undefs to init maybe-undefined status. * tree-ssa-loop-ivopts.cc (ssa_name_maybe_undef_p, ssa_name_set_maybe_undef, ssa_name_any_use_dominates_bb_p, mark_ssa_maybe_undefs): Move ... * tree-ssa.cc: ... here. * tree-ssa.h (ssa_name_any_use_dominates_bb_p, mark_ssa_maybe_undefs): Declare. (ssa_name_maybe_undef_p, ssa_name_set_maybe_undef): Define. * gcc.dg/torture/pr107833.c: New testcase. * gcc.dg/uninit-pr107839.c: Likewise. (cherry picked from commit 44c8402d35160515b3c09fd2bc239587e0c32a2b) Diff: --- gcc/cfghooks.cc | 1 + gcc/testsuite/gcc.dg/torture/pr107833.c | 33 ++++++++++ gcc/testsuite/gcc.dg/uninit-pr107839.c | 13 ++++ gcc/tree-ssa-loop-im.cc | 24 ++++++- gcc/tree-ssa-loop-ivopts.cc | 111 -------------------------------- gcc/tree-ssa.cc | 93 ++++++++++++++++++++++++++ gcc/tree-ssa.h | 25 +++++++ 7 files changed, 187 insertions(+), 113 deletions(-) diff --git a/gcc/cfghooks.cc b/gcc/cfghooks.cc index e435891fac6..c0b7bdcd9b2 100644 --- a/gcc/cfghooks.cc +++ b/gcc/cfghooks.cc @@ -29,6 +29,7 @@ along with GCC; see the file COPYING3. If not see #include "diagnostic-core.h" #include "dumpfile.h" #include "cfganal.h" +#include "tree.h" #include "tree-ssa.h" #include "cfgloop.h" #include "sreal.h" diff --git a/gcc/testsuite/gcc.dg/torture/pr107833.c b/gcc/testsuite/gcc.dg/torture/pr107833.c new file mode 100644 index 00000000000..0edf7c328ba --- /dev/null +++ b/gcc/testsuite/gcc.dg/torture/pr107833.c @@ -0,0 +1,33 @@ +/* { dg-do run } */ + +int a, b[1] = { 0 }, c, *d = b, e, *f, g; + +__attribute__((noipa)) int +foo (const char *x) +{ + (void) x; + return 0; +} + +int +main () +{ + for (int h = 0; a < 2; a++) + { + int i; + for (g = 0; g < 2; g++) + if (a < h) + { + e = i % 2; + c = *f; + } + for (h = 0; h < 3; h++) + { + if (d) + break; + i--; + foo ("0"); + } + } + return 0; +} diff --git a/gcc/testsuite/gcc.dg/uninit-pr107839.c b/gcc/testsuite/gcc.dg/uninit-pr107839.c new file mode 100644 index 00000000000..c2edcfaee22 --- /dev/null +++ b/gcc/testsuite/gcc.dg/uninit-pr107839.c @@ -0,0 +1,13 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -Wuninitialized" } */ + +int f (int); +void g (int c) +{ + int v; + if (c) + v = f(0); + while (1) + if (c) + f(v + v); /* { dg-bogus "uninitialized" } */ +} diff --git a/gcc/tree-ssa-loop-im.cc b/gcc/tree-ssa-loop-im.cc index 6d9316eed1f..3926e5c14a4 100644 --- a/gcc/tree-ssa-loop-im.cc +++ b/gcc/tree-ssa-loop-im.cc @@ -46,6 +46,7 @@ along with GCC; see the file COPYING3. If not see #include "alias.h" #include "builtins.h" #include "tree-dfa.h" +#include "tree-ssa.h" #include "dbgcnt.h" /* TODO: Support for predicated code motion. I.e. @@ -331,8 +332,8 @@ enum move_pos because it may trap), return MOVE_PRESERVE_EXECUTION. Otherwise return MOVE_IMPOSSIBLE. */ -enum move_pos -movement_possibility (gimple *stmt) +static enum move_pos +movement_possibility_1 (gimple *stmt) { tree lhs; enum move_pos ret = MOVE_POSSIBLE; @@ -422,6 +423,23 @@ movement_possibility (gimple *stmt) return ret; } +static enum move_pos +movement_possibility (gimple *stmt) +{ + enum move_pos pos = movement_possibility_1 (stmt); + if (pos == MOVE_POSSIBLE) + { + use_operand_p use_p; + ssa_op_iter ssa_iter; + FOR_EACH_PHI_OR_STMT_USE (use_p, stmt, ssa_iter, SSA_OP_USE) + if (TREE_CODE (USE_FROM_PTR (use_p)) == SSA_NAME + && ssa_name_maybe_undef_p (USE_FROM_PTR (use_p))) + return MOVE_PRESERVE_EXECUTION; + } + return pos; +} + + /* Compare the profile count inequality of bb and loop's preheader, it is three-state as stated in profile-count.h, FALSE is returned if inequality cannot be decided. */ @@ -3524,6 +3542,8 @@ loop_invariant_motion_in_fun (function *fun, bool store_motion) tree_ssa_lim_initialize (store_motion); + mark_ssa_maybe_undefs (); + /* Gathers information about memory accesses in the loops. */ analyze_memory_references (store_motion); diff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc index 549168aebd6..a67f5d549e6 100644 --- a/gcc/tree-ssa-loop-ivopts.cc +++ b/gcc/tree-ssa-loop-ivopts.cc @@ -3071,117 +3071,6 @@ get_loop_invariant_expr (struct ivopts_data *data, tree inv_expr) return *slot; } -/* Return TRUE iff VAR is marked as maybe-undefined. See - mark_ssa_maybe_undefs. */ - -static inline bool -ssa_name_maybe_undef_p (tree var) -{ - gcc_checking_assert (TREE_CODE (var) == SSA_NAME); - return TREE_VISITED (var); -} - -/* Set (or clear, depending on VALUE) VAR's maybe-undefined mark. */ - -static inline void -ssa_name_set_maybe_undef (tree var, bool value = true) -{ - gcc_checking_assert (TREE_CODE (var) == SSA_NAME); - TREE_VISITED (var) = value; -} - -/* Return TRUE iff there are any non-PHI uses of VAR that dominate the - end of BB. If we return TRUE and BB is a loop header, then VAR we - be assumed to be defined within the loop, even if it is marked as - maybe-undefined. */ - -static inline bool -ssa_name_any_use_dominates_bb_p (tree var, basic_block bb) -{ - imm_use_iterator iter; - use_operand_p use_p; - FOR_EACH_IMM_USE_FAST (use_p, iter, var) - { - if (is_a (USE_STMT (use_p)) - || is_gimple_debug (USE_STMT (use_p))) - continue; - basic_block dombb = gimple_bb (USE_STMT (use_p)); - if (dominated_by_p (CDI_DOMINATORS, bb, dombb)) - return true; - } - - return false; -} - -/* Mark as maybe_undef any SSA_NAMEs that are unsuitable as ivopts - candidates for potentially involving undefined behavior. */ - -static void -mark_ssa_maybe_undefs (void) -{ - auto_vec queue; - - /* Scan all SSA_NAMEs, marking the definitely-undefined ones as - maybe-undefined and queuing them for propagation, while clearing - the mark on others. */ - unsigned int i; - tree var; - FOR_EACH_SSA_NAME (i, var, cfun) - { - if (SSA_NAME_IS_VIRTUAL_OPERAND (var) - || !ssa_undefined_value_p (var, false)) - ssa_name_set_maybe_undef (var, false); - else - { - ssa_name_set_maybe_undef (var); - queue.safe_push (var); - if (dump_file && (dump_flags & TDF_DETAILS)) - fprintf (dump_file, "marking _%i as maybe-undef\n", - SSA_NAME_VERSION (var)); - } - } - - /* Now propagate maybe-undefined from a DEF to any other PHI that - uses it, as long as there isn't any intervening use of DEF. */ - while (!queue.is_empty ()) - { - var = queue.pop (); - imm_use_iterator iter; - use_operand_p use_p; - FOR_EACH_IMM_USE_FAST (use_p, iter, var) - { - /* Any uses of VAR that aren't PHI args imply VAR must be - defined, otherwise undefined behavior would have been - definitely invoked. Only PHI args may hold - maybe-undefined values without invoking undefined - behavior for that reason alone. */ - if (!is_a (USE_STMT (use_p))) - continue; - gphi *phi = as_a (USE_STMT (use_p)); - - tree def = gimple_phi_result (phi); - if (ssa_name_maybe_undef_p (def)) - continue; - - /* Look for any uses of the maybe-unused SSA_NAME that - dominates the block that reaches the incoming block - corresponding to the PHI arg in which it is mentioned. - That means we can assume the SSA_NAME is defined in that - path, so we only mark a PHI result as maybe-undef if we - find an unused reaching SSA_NAME. */ - int idx = phi_arg_index_from_use (use_p); - basic_block bb = gimple_phi_arg_edge (phi, idx)->src; - if (ssa_name_any_use_dominates_bb_p (var, bb)) - continue; - - ssa_name_set_maybe_undef (def); - queue.safe_push (def); - if (dump_file && (dump_flags & TDF_DETAILS)) - fprintf (dump_file, "marking _%i as maybe-undef because of _%i\n", - SSA_NAME_VERSION (def), SSA_NAME_VERSION (var)); - } - } -} /* Return *TP if it is an SSA_NAME marked with TREE_VISITED, i.e., as unsuitable as ivopts candidates for potentially involving undefined diff --git a/gcc/tree-ssa.cc b/gcc/tree-ssa.cc index ab8b1c27ed4..d36d2273f9d 100644 --- a/gcc/tree-ssa.cc +++ b/gcc/tree-ssa.cc @@ -1400,6 +1400,99 @@ gimple_uses_undefined_value_p (gimple *stmt) } +/* Return TRUE iff there are any non-PHI uses of VAR that dominate the + end of BB. If we return TRUE and BB is a loop header, then VAR we + be assumed to be defined within the loop, even if it is marked as + maybe-undefined. */ + +bool +ssa_name_any_use_dominates_bb_p (tree var, basic_block bb) +{ + imm_use_iterator iter; + use_operand_p use_p; + FOR_EACH_IMM_USE_FAST (use_p, iter, var) + { + if (is_a (USE_STMT (use_p)) + || is_gimple_debug (USE_STMT (use_p))) + continue; + basic_block dombb = gimple_bb (USE_STMT (use_p)); + if (dominated_by_p (CDI_DOMINATORS, bb, dombb)) + return true; + } + + return false; +} + +/* Mark as maybe_undef any SSA_NAMEs that are unsuitable as ivopts + candidates for potentially involving undefined behavior. */ + +void +mark_ssa_maybe_undefs (void) +{ + auto_vec queue; + + /* Scan all SSA_NAMEs, marking the definitely-undefined ones as + maybe-undefined and queuing them for propagation, while clearing + the mark on others. */ + unsigned int i; + tree var; + FOR_EACH_SSA_NAME (i, var, cfun) + { + if (SSA_NAME_IS_VIRTUAL_OPERAND (var) + || !ssa_undefined_value_p (var, false)) + ssa_name_set_maybe_undef (var, false); + else + { + ssa_name_set_maybe_undef (var); + queue.safe_push (var); + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "marking _%i as maybe-undef\n", + SSA_NAME_VERSION (var)); + } + } + + /* Now propagate maybe-undefined from a DEF to any other PHI that + uses it, as long as there isn't any intervening use of DEF. */ + while (!queue.is_empty ()) + { + var = queue.pop (); + imm_use_iterator iter; + use_operand_p use_p; + FOR_EACH_IMM_USE_FAST (use_p, iter, var) + { + /* Any uses of VAR that aren't PHI args imply VAR must be + defined, otherwise undefined behavior would have been + definitely invoked. Only PHI args may hold + maybe-undefined values without invoking undefined + behavior for that reason alone. */ + if (!is_a (USE_STMT (use_p))) + continue; + gphi *phi = as_a (USE_STMT (use_p)); + + tree def = gimple_phi_result (phi); + if (ssa_name_maybe_undef_p (def)) + continue; + + /* Look for any uses of the maybe-unused SSA_NAME that + dominates the block that reaches the incoming block + corresponding to the PHI arg in which it is mentioned. + That means we can assume the SSA_NAME is defined in that + path, so we only mark a PHI result as maybe-undef if we + find an unused reaching SSA_NAME. */ + int idx = phi_arg_index_from_use (use_p); + basic_block bb = gimple_phi_arg_edge (phi, idx)->src; + if (ssa_name_any_use_dominates_bb_p (var, bb)) + continue; + + ssa_name_set_maybe_undef (def); + queue.safe_push (def); + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, "marking _%i as maybe-undef because of _%i\n", + SSA_NAME_VERSION (def), SSA_NAME_VERSION (var)); + } + } +} + /* If necessary, rewrite the base of the reference tree *TP from a MEM_REF to a plain or converted symbol. */ diff --git a/gcc/tree-ssa.h b/gcc/tree-ssa.h index 008535454a8..19c1eedc9f9 100644 --- a/gcc/tree-ssa.h +++ b/gcc/tree-ssa.h @@ -55,6 +55,31 @@ extern tree find_released_ssa_name (tree *, int *, void *); extern bool ssa_defined_default_def_p (tree t); extern bool ssa_undefined_value_p (tree, bool = true); extern bool gimple_uses_undefined_value_p (gimple *); + + +bool ssa_name_any_use_dominates_bb_p (tree var, basic_block bb); +extern void mark_ssa_maybe_undefs (void); + +/* Return TRUE iff VAR is marked as maybe-undefined. See + mark_ssa_maybe_undefs. */ + +static inline bool +ssa_name_maybe_undef_p (tree var) +{ + gcc_checking_assert (TREE_CODE (var) == SSA_NAME); + return TREE_VISITED (var); +} + +/* Set (or clear, depending on VALUE) VAR's maybe-undefined mark. */ + +static inline void +ssa_name_set_maybe_undef (tree var, bool value = true) +{ + gcc_checking_assert (TREE_CODE (var) == SSA_NAME); + TREE_VISITED (var) = value; +} + + extern void execute_update_addresses_taken (void); /* Given an edge_var_map V, return the PHI arg definition. */