https://gcc.gnu.org/g:1ddd9f9e53bd649d3d236f7941106d8cc46e7358
commit r12-10293-g1ddd9f9e53bd649d3d236f7941106d8cc46e7358
Author: Richard Biener <rguent...@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 749587eae5e..b6ba81c9c29 100644
--- a/gcc/generic-match-head.cc
+++ b/gcc/generic-match-head.cc
@@ -39,6 +39,8 @@ along with GCC; see the file COPYING3. If not see
#include "dbgcnt.h"
#include "tm.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 1c74d38088f..2fd27fcbacc 100644
--- a/gcc/gimple-match-head.cc
+++ b/gcc/gimple-match-head.cc
@@ -45,6 +45,8 @@ along with GCC; see the file COPYING3. If not see
#include "dbgcnt.h"
#include "tm.h"
#include "gimple-range.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 a9aae484b2b..843b939fc34 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -904,6 +904,16 @@ 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); })))
+
/* Fold (1 << (C - x)) where C = precision(type) - 1
into ((1 << C) >> x). */
(simplify
