* [PATCH] tree-optimization/91838 - fix FAIL of g++.dg/opt/pr91838.C @ 2023-07-27 12:00 Richard Biener 0 siblings, 0 replies; 4+ messages in thread From: Richard Biener @ 2023-07-27 12:00 UTC (permalink / raw) To: gcc-patches; +Cc: Jakub Jelinek The following fixes the lack of simplification of a vector shift by an out-of-bounds shift value. For scalars this is done both by CCP and VRP but vectors are not handled there. This results in PR91838 differences in outcome dependent on whether a vector shift ISA is available and thus vector lowering does or does not expose scalar shifts here. The following adds a match.pd pattern to catch uniform out-of-bound shifts, simplifying them to zero when not sanitizing shift amounts. Bootstrapped and tested on x86_64-unknown-linux-gnu. OK? Thanks, Richard. PR tree-optimization/91838 * match.pd (([rl]shift @0 out-of-bounds) -> zero): New pattern. --- gcc/match.pd | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/gcc/match.pd b/gcc/match.pd index a443dc48634..eace7d635e7 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -1059,6 +1059,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) && tree_nop_conversion_p (type, TREE_TYPE (@1))) (lshift @0 @2))) +/* Shifts by precision or greater result in zero. */ +(for shift (lshift rshift) + (simplify + (shift @0 uniform_integer_cst_p@1) + (if (!(flag_sanitize & SANITIZE_SHIFT_EXPONENT) + /* Use a signed compare to leave negative shift counts alone. */ + && wi::ges_p (wi::to_wide (uniform_integer_cst_p (@1)), + element_precision (type))) + { build_zero_cst (type); }))) + /* Shifts by constants distribute over several binary operations, hence (X << C) + (Y << C) can be simplified to (X + Y) << C. */ (for op (plus minus) -- 2.35.3 ^ permalink raw reply [flat|nested] 4+ messages in thread
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* Re: [PATCH] tree-optimization/91838 - fix FAIL of g++.dg/opt/pr91838.C [not found] <81140.123072708005901359@us-mta-160.us.mimecast.lan> @ 2023-07-27 12:30 ` Jakub Jelinek 2023-07-27 13:07 ` Richard Biener 0 siblings, 1 reply; 4+ messages in thread From: Jakub Jelinek @ 2023-07-27 12:30 UTC (permalink / raw) To: Richard Biener; +Cc: gcc-patches On Thu, Jul 27, 2023 at 12:00:56PM +0000, Richard Biener wrote: > The following fixes the lack of simplification of a vector shift > by an out-of-bounds shift value. For scalars this is done both > by CCP and VRP but vectors are not handled there. This results > in PR91838 differences in outcome dependent on whether a vector > shift ISA is available and thus vector lowering does or does not > expose scalar shifts here. > > The following adds a match.pd pattern to catch uniform out-of-bound > shifts, simplifying them to zero when not sanitizing shift amounts. > > Bootstrapped and tested on x86_64-unknown-linux-gnu. > > OK? > > Thanks, > Richard. > > PR tree-optimization/91838 > * match.pd (([rl]shift @0 out-of-bounds) -> zero): New pattern. The !(flag_sanitize & SANITIZE_SHIFT_EXPONENT) should be !sanitize_flags_p (SANITIZE_SHIFT_EXPONENT) or maybe even GIMPLE || !sanitize_flags_p (SANITIZE_SHIFT_EXPONENT) because the shift ubsan instrumentation is done on GENERIC, so it can be optimized on GIMPLE even with ubsan. Otherwise LGTM. Jakub ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] tree-optimization/91838 - fix FAIL of g++.dg/opt/pr91838.C 2023-07-27 12:30 ` Jakub Jelinek @ 2023-07-27 13:07 ` Richard Biener 2023-07-27 13:09 ` Jakub Jelinek 0 siblings, 1 reply; 4+ messages in thread From: Richard Biener @ 2023-07-27 13:07 UTC (permalink / raw) To: Jakub Jelinek; +Cc: gcc-patches On Thu, 27 Jul 2023, Jakub Jelinek wrote: > On Thu, Jul 27, 2023 at 12:00:56PM +0000, Richard Biener wrote: > > The following fixes the lack of simplification of a vector shift > > by an out-of-bounds shift value. For scalars this is done both > > by CCP and VRP but vectors are not handled there. This results > > in PR91838 differences in outcome dependent on whether a vector > > shift ISA is available and thus vector lowering does or does not > > expose scalar shifts here. > > > > The following adds a match.pd pattern to catch uniform out-of-bound > > shifts, simplifying them to zero when not sanitizing shift amounts. > > > > Bootstrapped and tested on x86_64-unknown-linux-gnu. > > > > OK? > > > > Thanks, > > Richard. > > > > PR tree-optimization/91838 > > * match.pd (([rl]shift @0 out-of-bounds) -> zero): New pattern. > > The !(flag_sanitize & SANITIZE_SHIFT_EXPONENT) > should be !sanitize_flags_p (SANITIZE_SHIFT_EXPONENT) > or maybe even > GIMPLE || !sanitize_flags_p (SANITIZE_SHIFT_EXPONENT) > because the shift ubsan instrumentation is done on GENERIC, so it can be > optimized on GIMPLE even with ubsan. > > Otherwise LGTM. So like the following, will push after re-testing succeeded. Thanks, Richard. From c6d348acdc2143fc4c2849e33075a3975fe29b26 Mon Sep 17 00:00:00 2001 From: Richard Biener <rguenther@suse.de> Date: Thu, 27 Jul 2023 13:08:32 +0200 Subject: [PATCH] tree-optimization/91838 - fix FAIL of g++.dg/opt/pr91838.C To: gcc-patches@gcc.gnu.org The following fixes the lack of simplification of a vector shift by an out-of-bounds shift value. For scalars this is done both by CCP and VRP but vectors are not handled there. This results in PR91838 differences in outcome dependent on whether a vector shift ISA is available and thus vector lowering does or does not expose scalar shifts here. The following adds a match.pd pattern to catch uniform out-of-bound shifts, simplifying them to zero when not sanitizing shift amounts. PR tree-optimization/91838 * gimple-match-head.cc: Include attribs.h and asan.h. * generic-match-head.cc: Likewise. * match.pd (([rl]shift @0 out-of-bounds) -> zero): New pattern. --- gcc/generic-match-head.cc | 2 ++ gcc/gimple-match-head.cc | 2 ++ gcc/match.pd | 10 ++++++++++ 3 files changed, 14 insertions(+) diff --git a/gcc/generic-match-head.cc b/gcc/generic-match-head.cc index b4b5bc88f4b..a71c0727b0b 100644 --- a/gcc/generic-match-head.cc +++ b/gcc/generic-match-head.cc @@ -41,6 +41,8 @@ along with GCC; see the file COPYING3. If not see #include "tree-eh.h" #include "langhooks.h" #include "tree-pass.h" +#include "attribs.h" +#include "asan.h" /* Routine to determine if the types T1 and T2 are effectively the same for GENERIC. If T1 or T2 is not a type, the test diff --git a/gcc/gimple-match-head.cc b/gcc/gimple-match-head.cc index d795066e53e..5d6d26d009b 100644 --- a/gcc/gimple-match-head.cc +++ b/gcc/gimple-match-head.cc @@ -47,6 +47,8 @@ along with GCC; see the file COPYING3. If not see #include "tm.h" #include "gimple-range.h" #include "langhooks.h" +#include "attribs.h" +#include "asan.h" tree do_valueize (tree, tree (*)(tree), bool &); tree do_valueize (tree (*)(tree), tree); diff --git a/gcc/match.pd b/gcc/match.pd index a443dc48634..fcb1a735507 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -1059,6 +1059,16 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) && tree_nop_conversion_p (type, TREE_TYPE (@1))) (lshift @0 @2))) +/* Shifts by precision or greater result in zero. */ +(for shift (lshift rshift) + (simplify + (shift @0 uniform_integer_cst_p@1) + (if ((GIMPLE || !sanitize_flags_p (SANITIZE_SHIFT_EXPONENT)) + /* Use a signed compare to leave negative shift counts alone. */ + && wi::ges_p (wi::to_wide (uniform_integer_cst_p (@1)), + element_precision (type))) + { build_zero_cst (type); }))) + /* Shifts by constants distribute over several binary operations, hence (X << C) + (Y << C) can be simplified to (X + Y) << C. */ (for op (plus minus) -- 2.35.3 k ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] tree-optimization/91838 - fix FAIL of g++.dg/opt/pr91838.C 2023-07-27 13:07 ` Richard Biener @ 2023-07-27 13:09 ` Jakub Jelinek 0 siblings, 0 replies; 4+ messages in thread From: Jakub Jelinek @ 2023-07-27 13:09 UTC (permalink / raw) To: Richard Biener; +Cc: gcc-patches On Thu, Jul 27, 2023 at 01:07:58PM +0000, Richard Biener wrote: > On Thu, 27 Jul 2023, Jakub Jelinek wrote: > > > On Thu, Jul 27, 2023 at 12:00:56PM +0000, Richard Biener wrote: > > > The following fixes the lack of simplification of a vector shift > > > by an out-of-bounds shift value. For scalars this is done both > > > by CCP and VRP but vectors are not handled there. This results > > > in PR91838 differences in outcome dependent on whether a vector > > > shift ISA is available and thus vector lowering does or does not > > > expose scalar shifts here. > > > > > > The following adds a match.pd pattern to catch uniform out-of-bound > > > shifts, simplifying them to zero when not sanitizing shift amounts. > > > > > > Bootstrapped and tested on x86_64-unknown-linux-gnu. > > > > > > OK? > > > > > > Thanks, > > > Richard. > > > > > > PR tree-optimization/91838 > > > * match.pd (([rl]shift @0 out-of-bounds) -> zero): New pattern. > > > > The !(flag_sanitize & SANITIZE_SHIFT_EXPONENT) > > should be !sanitize_flags_p (SANITIZE_SHIFT_EXPONENT) > > or maybe even > > GIMPLE || !sanitize_flags_p (SANITIZE_SHIFT_EXPONENT) > > because the shift ubsan instrumentation is done on GENERIC, so it can be > > optimized on GIMPLE even with ubsan. > > > > Otherwise LGTM. > > So like the following, will push after re-testing succeeded. Yes, thanks. Jakub ^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-07-27 12:00 [PATCH] tree-optimization/91838 - fix FAIL of g++.dg/opt/pr91838.C Richard Biener
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