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* [gcc r13-8498] tree-optimization/91838 - fix FAIL of g++.dg/opt/pr91838.C
@ 2024-03-26 14:58 Andre Simoes Dias Vieira
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From: Andre Simoes Dias Vieira @ 2024-03-26 14:58 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:c6e171ff827f8ff1bd160babac0dd24933972664
commit r13-8498-gc6e171ff827f8ff1bd160babac0dd24933972664
Author: Richard Biener <rguenther@suse.de>
Date: Thu Jul 27 13:08:32 2023 +0200
tree-optimization/91838 - fix FAIL of g++.dg/opt/pr91838.C
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.
(cherry picked from commit d1c072a1c3411a6fe29900750b38210af8451eeb)
Diff:
---
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 f011204c5be..36f1832a05d 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 ec603f9d043..21843d7870b 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"
/* Forward declarations of the private auto-generated matchers.
They expect valueized operands in canonical order and do not
diff --git a/gcc/match.pd b/gcc/match.pd
index 908959de3e7..6812853df67 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -997,6 +997,16 @@ 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)
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