From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 2140) id 4CAC03858C74; Thu, 27 Apr 2023 05:59:31 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 4CAC03858C74 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1682575171; bh=8i2KNpV6LtezacGP4z/BCSSE2yyiyUNfwvPkIelLo5A=; h=From:To:Subject:Date:From; b=E9k0bJbzRcqhd14llImARR/C9QurxANg/nq/RSWHR/uB39Nv6WTDtMNGojv20b2M9 mCGdJYlRvsUd0E2KV+XlxZ/idYPvJzdxtVymeNLiEX4uTZFMQc+gV6ndeMIUD6jCg4 /maH+uiqOvuTAmKhpy2wrSlDVwlqkFkWKJavl0QQ= Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: Alexandre Oliva To: gcc-cvs@gcc.gnu.org Subject: [gcc(refs/users/aoliva/heads/testme)] harden-conditionals: detach values before compares X-Act-Checkin: gcc X-Git-Author: Alexandre Oliva X-Git-Refname: refs/users/aoliva/heads/testme X-Git-Oldrev: 95d4c0d2e6318aef88ba0bc607dfc1ec6b7a612f X-Git-Newrev: 4938d296e8735c9b8d2dc151236fe302b4c2b546 Message-Id: <20230427055931.4CAC03858C74@sourceware.org> Date: Thu, 27 Apr 2023 05:59:31 +0000 (GMT) List-Id: https://gcc.gnu.org/g:4938d296e8735c9b8d2dc151236fe302b4c2b546 commit 4938d296e8735c9b8d2dc151236fe302b4c2b546 Author: Alexandre Oliva Date: Thu Apr 27 02:43:48 2023 -0300 harden-conditionals: detach values before compares The optimization barriers inserted after compares enable GCC to derive information about the values from e.g. the taken paths, or the absence of exceptions. Move them before the original compares, so that the reversed compares test copies of the original operands, without further optimizations. for gcc/ChangeLog * gimple-harden-conditionals.cc (insert_edge_check_and_trap): Move detach value calls... (pass_harden_conditional_branches::execute): ... here. (pass_harden_compares::execute): Detach values before compares. for gcc/testsuite/ChangeLog * c-c++-common/torture/harden-cond-comp.c: New. TN: W420-020 Diff: --- gcc/gimple-harden-conditionals.cc | 25 +++++++++++++--------- .../c-c++-common/torture/harden-cond-comp.c | 24 +++++++++++++++++++++ 2 files changed, 39 insertions(+), 10 deletions(-) diff --git a/gcc/gimple-harden-conditionals.cc b/gcc/gimple-harden-conditionals.cc index 78b8d5692d7..2e5a42e9e71 100644 --- a/gcc/gimple-harden-conditionals.cc +++ b/gcc/gimple-harden-conditionals.cc @@ -276,8 +276,8 @@ insert_check_and_trap (location_t loc, gimple_stmt_iterator *gsip, } /* Split edge E, and insert_check_and_trap (see above) in the - newly-created block, using detached copies of LHS's and RHS's - values (see detach_value above) for the COP compare. */ + newly-created block, using already-detached copies of LHS's and + RHS's values (see detach_value above) for the COP compare. */ static inline void insert_edge_check_and_trap (location_t loc, edge e, @@ -301,10 +301,6 @@ insert_edge_check_and_trap (location_t loc, edge e, gimple_stmt_iterator gsik = gsi_after_labels (chk); - bool same_p = (lhs == rhs); - lhs = detach_value (loc, &gsik, lhs); - rhs = same_p ? lhs : detach_value (loc, &gsik, rhs); - insert_check_and_trap (loc, &gsik, flags, cop, lhs, rhs); } @@ -366,6 +362,12 @@ pass_harden_conditional_branches::execute (function *fun) /* ??? Can we do better? */ continue; + /* Detach the values before the compares. If we do so later, + the compiler may use values inferred from the compares. */ + bool same_p = (lhs == rhs); + lhs = detach_value (loc, &gsi, lhs); + rhs = same_p ? lhs : detach_value (loc, &gsi, rhs); + insert_edge_check_and_trap (loc, EDGE_SUCC (bb, 0), cop, lhs, rhs); insert_edge_check_and_trap (loc, EDGE_SUCC (bb, 1), cop, lhs, rhs); } @@ -508,6 +510,13 @@ pass_harden_compares::execute (function *fun) tree rhs = copy_ssa_name (lhs); + /* Detach the values before the compares, so that the + compiler infers nothing from them, not even from a + throwing compare that didn't throw. */ + bool same_p = (op1 == op2); + op1 = detach_value (loc, &gsi, op1); + op2 = same_p ? op1 : detach_value (loc, &gsi, op2); + gimple_stmt_iterator gsi_split = gsi; /* Don't separate the original assignment from debug stmts that might be associated with it, and arrange to split the @@ -529,10 +538,6 @@ pass_harden_compares::execute (function *fun) gimple_bb (asgn)->index, nbb->index); } - bool same_p = (op1 == op2); - op1 = detach_value (loc, &gsi_split, op1); - op2 = same_p ? op1 : detach_value (loc, &gsi_split, op2); - gassign *asgnck = gimple_build_assign (rhs, cop, op1, op2); gimple_set_location (asgnck, loc); gsi_insert_before (&gsi_split, asgnck, GSI_SAME_STMT); diff --git a/gcc/testsuite/c-c++-common/torture/harden-cond-comp.c b/gcc/testsuite/c-c++-common/torture/harden-cond-comp.c new file mode 100644 index 00000000000..5aad890a1d3 --- /dev/null +++ b/gcc/testsuite/c-c++-common/torture/harden-cond-comp.c @@ -0,0 +1,24 @@ +/* { dg-do compile } */ +/* { dg-options "-fharden-conditional-branches -fharden-compares -fdump-tree-hardcbr -fdump-tree-hardcmp -ffat-lto-objects" } */ + +int f(int i, int j) { + if (i == 0) + return j != 0; + else + return i * j != 0; +} + +/* { dg-final { scan-tree-dump-times "Splitting edge" 2 "hardcbr" } } */ +/* { dg-final { scan-tree-dump-times "Adding reversed compare" 2 "hardcbr" } } */ +/* { dg-final { scan-tree-dump-times "__builtin_trap" 2 "hardcbr" } } */ + +/* { dg-final { scan-tree-dump-times "Splitting block" 2 "hardcmp" } } */ +/* { dg-final { scan-tree-dump-times "Adding reversed compare" 2 "hardcmp" } } */ +/* { dg-final { scan-tree-dump-times "__builtin_trap" 4 "hardcmp" } } */ + +/* Check that the optimization barrier is placed before the original compare. */ +/* { dg-final { scan-tree-dump-times {__asm__[(]"" : "=g" _[0-9]* : "0" i_[0-9]*[(]D[)][)][;][\n][ ]*if [(]i_[0-9]*[(]D[)] == 0[)]} 1 "hardcbr" } } */ +/* { dg-final { scan-tree-dump-times {if [(]_[0-9]* != 0[)]} 2 "hardcbr" } } */ + +/* { dg-final { scan-tree-dump-times {__asm__[(]"" : "=g" _[0-9]* : "0" j_[0-9]*[(]D[)][)][;][\n][ ]*_[0-9]* = j_[0-9]*[(]D[)] != 0;[\n] *_[0-9]* = _[0-9]* == 0} 1 "hardcmp" } } */ +/* { dg-final { scan-tree-dump-times {__asm__[(]"" : "=g" _[0-9]* : "0" _[0-9]*[)][;][\n][ ]*_[0-9]* = _[0-9]* != 0;[\n] *_[0-9]* = _[0-9]* == 0} 1 "hardcmp" } } */