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* [gcc r11-8139] combine: Don't fold away side-effects in simplify_and_const_int_1 [PR99830]
@ 2021-04-12 23:01 Jakub Jelinek
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From: Jakub Jelinek @ 2021-04-12 23:01 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:9c1c8ad8339d551ac91a7af5614f29b9a687189a
commit r11-8139-g9c1c8ad8339d551ac91a7af5614f29b9a687189a
Author: Jakub Jelinek <jakub@redhat.com>
Date: Tue Apr 13 01:00:48 2021 +0200
combine: Don't fold away side-effects in simplify_and_const_int_1 [PR99830]
Here is an alternate patch for the PR99830 bug.
As discussed on IRC and in the PR, the reason why a (clobber:TI (const_int 0))
has been propagated into the debug insns is that it got optimized away
during simplification from the i3 instruction pattern.
And that happened because
simplify_and_const_int_1 (SImode, varop, 255)
with varop of
(ashift:SI (subreg:SI (and:TI (clobber:TI (const_int 0 [0]))
(const_int 255 [0xff])) 0)
(const_int 16 [0x10]))
was called and through nonzero_bits determined that (whatever << 16) & 255
is const0_rtx.
It is, but if there are side-effects in varop and such clobbers are
considered as such, we shouldn't optimize those away.
2021-04-13 Jakub Jelinek <jakub@redhat.com>
PR debug/99830
* combine.c (simplify_and_const_int_1): Don't optimize varop
away if it has side-effects.
* gcc.dg/pr99830.c: New test.
Diff:
---
gcc/combine.c | 2 +-
gcc/testsuite/gcc.dg/pr99830.c | 10 ++++++++++
2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/gcc/combine.c b/gcc/combine.c
index 3294575357b..dffa3b0390b 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -10153,7 +10153,7 @@ simplify_and_const_int_1 (scalar_int_mode mode, rtx varop,
constop &= nonzero;
/* If we don't have any bits left, return zero. */
- if (constop == 0)
+ if (constop == 0 && !side_effects_p (varop))
return const0_rtx;
/* If VAROP is a NEG of something known to be zero or 1 and CONSTOP is
diff --git a/gcc/testsuite/gcc.dg/pr99830.c b/gcc/testsuite/gcc.dg/pr99830.c
new file mode 100644
index 00000000000..75226f5c3a9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr99830.c
@@ -0,0 +1,10 @@
+/* PR debug/99830 */
+/* { dg-do compile { target int128 } } */
+/* { dg-options "-O2 -fno-expensive-optimizations -fno-split-wide-types -g" } */
+
+int foo (long a, __int128 b, short c, int d, unsigned e, __int128 f)
+{
+ __builtin_memmove (2 + (char *) &f, foo, 1);
+ c >>= (char) f;
+ return c;
+}
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