* [Bug middle-end/103431] [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts
2021-11-25 21:11 [Bug rtl-optimization/103431] New: [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts zsojka at seznam dot cz
@ 2021-11-25 21:31 ` pinskia at gcc dot gnu.org
2021-11-26 7:23 ` rguenth at gcc dot gnu.org
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From: pinskia at gcc dot gnu.org @ 2021-11-25 21:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103431
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Component|rtl-optimization |middle-end
Last reconfirmed| |2021-11-25
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Confirmed.
reduced testcase (removing the globals):
typedef unsigned __int128 B;
__attribute__((noipa))
void f(unsigned short a)
{
B b = 5;
int size = (sizeof(b)*8)-1;
a /= 0xfffffffd;
B b1 = (b << (a & size) | b >> (-(a & size) & size));
if (b1 != 5)
__builtin_abort ();
}
int
main (void)
{
f(0);
}
----- CUT ---
The gimple level does not change. In GCC 11 and the trunk, we have:
_1 = (unsigned intD.9) a_8(D);
_2 = _1 / 4294967293;
a_9 = (short unsigned intD.18) _2;
_13 = a_9 & 127;
_3 = (intD.6) _13;
b1_10 = 5 r<< _3;
if (b1_10 != 5)
It looks like the expansion from gimple to RTL of the rotate is different
between the two versions.
^ permalink raw reply [flat|nested] 10+ messages in thread* [Bug middle-end/103431] [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts
2021-11-25 21:11 [Bug rtl-optimization/103431] New: [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts zsojka at seznam dot cz
2021-11-25 21:31 ` [Bug middle-end/103431] " pinskia at gcc dot gnu.org
@ 2021-11-26 7:23 ` rguenth at gcc dot gnu.org
2021-11-26 9:38 ` [Bug middle-end/103431] [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts since r12-4853-g2a83259f837e5cbd marxin at gcc dot gnu.org
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From: rguenth at gcc dot gnu.org @ 2021-11-26 7:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103431
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Priority|P3 |P1
Keywords| |needs-bisection
Target Milestone|--- |12.0
^ permalink raw reply [flat|nested] 10+ messages in thread* [Bug middle-end/103431] [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts since r12-4853-g2a83259f837e5cbd
2021-11-25 21:11 [Bug rtl-optimization/103431] New: [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts zsojka at seznam dot cz
2021-11-25 21:31 ` [Bug middle-end/103431] " pinskia at gcc dot gnu.org
2021-11-26 7:23 ` rguenth at gcc dot gnu.org
@ 2021-11-26 9:38 ` marxin at gcc dot gnu.org
2021-11-26 10:21 ` jakub at gcc dot gnu.org
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From: marxin at gcc dot gnu.org @ 2021-11-26 9:38 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103431
--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r12-4853-g2a83259f837e5cbd .
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2021-11-25 21:11 [Bug rtl-optimization/103431] New: [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts zsojka at seznam dot cz
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2021-11-26 9:38 ` [Bug middle-end/103431] [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts since r12-4853-g2a83259f837e5cbd marxin at gcc dot gnu.org
@ 2021-11-26 10:21 ` jakub at gcc dot gnu.org
2021-11-26 11:40 ` jakub at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-11-26 10:21 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103431
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I'll have a look.
^ permalink raw reply [flat|nested] 10+ messages in thread* [Bug middle-end/103431] [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts since r12-4853-g2a83259f837e5cbd
2021-11-25 21:11 [Bug rtl-optimization/103431] New: [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts zsojka at seznam dot cz
` (3 preceding siblings ...)
2021-11-26 10:21 ` jakub at gcc dot gnu.org
@ 2021-11-26 11:40 ` jakub at gcc dot gnu.org
2021-11-26 13:34 ` jakub at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-11-26 11:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103431
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org
Status|NEW |ASSIGNED
--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The bug is in the x86*_shld and x86*_shrd patterns.
[(set (match_operand:SI 0 "nonimmediate_operand" "+r*m")
(ior:SI (ashift:SI (match_dup 0)
(match_operand:QI 2 "nonmemory_operand" "Ic"))
(lshiftrt:SI (match_operand:SI 1 "register_operand" "r")
(minus:QI (const_int 32) (match_dup 2)))))
(clobber (reg:CC FLAGS_REG))]
doesn't correctly describe what the instructions do if operands[2] is zero,
because 32 - 0 is an out of bounds shift.
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2021-11-25 21:11 [Bug rtl-optimization/103431] New: [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts zsojka at seznam dot cz
` (4 preceding siblings ...)
2021-11-26 11:40 ` jakub at gcc dot gnu.org
@ 2021-11-26 13:34 ` jakub at gcc dot gnu.org
2021-11-26 15:39 ` jakub at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-11-26 13:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103431
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 51881
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51881&action=edit
gcc12-pr103431-wip.patch
I've tried this, but that is actually incorrect too.
Because for operands[1], what we actually want for operands[2] of 0 is not
shift by 0, but actually not or the operand in.
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2021-11-25 21:11 [Bug rtl-optimization/103431] New: [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts zsojka at seznam dot cz
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2021-11-26 13:34 ` jakub at gcc dot gnu.org
@ 2021-11-26 15:39 ` jakub at gcc dot gnu.org
2021-11-27 12:02 ` cvs-commit at gcc dot gnu.org
2021-11-27 12:03 ` jakub at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-11-26 15:39 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103431
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Attachment #51881|0 |1
is obsolete| |
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 51883
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51883&action=edit
gcc12-pr103431.patch
This patch seems to work though. Untested so far.
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2021-11-25 21:11 [Bug rtl-optimization/103431] New: [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts zsojka at seznam dot cz
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2021-11-26 15:39 ` jakub at gcc dot gnu.org
@ 2021-11-27 12:02 ` cvs-commit at gcc dot gnu.org
2021-11-27 12:03 ` jakub at gcc dot gnu.org
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From: cvs-commit at gcc dot gnu.org @ 2021-11-27 12:02 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103431
--- Comment #7 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:
https://gcc.gnu.org/g:f7e4f57f1c7883721b6f5ad48953e10ebfb5a756
commit r12-5558-gf7e4f57f1c7883721b6f5ad48953e10ebfb5a756
Author: Jakub Jelinek <jakub@redhat.com>
Date: Sat Nov 27 13:02:06 2021 +0100
x86: Fix up x86_{,64_}sh{l,r}d patterns [PR103431]
The following testcase is miscompiled because the x86_{,64_}sh{l,r}d
patterns don't properly describe what the instructions do. One thing
is left out, in particular that there is initial count &= 63 for
sh{l,r}dq and initial count &= 31 for sh{l,r}d{l,w}. And another thing
not described properly, in particular the behavior when count (after the
masking) is 0. The pattern says it is e.g.
res = (op0 << op2) | (op1 >> (64 - op2))
but that triggers UB on op1 >> 64. For op2 0 we actually want
res = (op0 << op2) | 0
When constants are propagated to these patterns during RTL optimizations,
both such problems trigger wrong-code issues.
This patch represents the patterns as e.g.
res = (op0 << (op2 & 63)) | (unsigned long long) ((uint128_t) op1 >> (64 -
(op2 & 63)))
so there is both the initial masking and op2 == 0 behavior results in
zero being ored.
The patch introduces alternate patterns for constant op2 where
simplify-rtx.c will fold those expressions into simple numbers,
and define_insn_and_split pre-reload splitter for how the patterns
looked before into the new form, so that it can pattern match during
combine even computations that assumed the shift amount will be in
the range of 1 .. bitsize-1.
2021-11-27 Jakub Jelinek <jakub@redhat.com>
PR middle-end/103431
* config/i386/i386.md (x86_64_shld, x86_shld, x86_64_shrd,
x86_shrd):
Change insn pattern to accurately describe the instructions.
(*x86_64_shld_1, *x86_shld_1, *x86_64_shrd_1, *x86_shrd_1): New
define_insn patterns.
(*x86_64_shld_2, *x86_shld_2, *x86_64_shrd_2, *x86_shrd_2): New
define_insn_and_split patterns.
(*ashl<dwi>3_doubleword_mask, *ashl<dwi>3_doubleword_mask_1,
*<insn><dwi>3_doubleword_mask, *<insn><dwi>3_doubleword_mask_1,
ix86_rotl<dwi>3_doubleword, ix86_rotr<dwi>3_doubleword): Adjust
splitters for x86_{,64_}sh{l,r}d pattern changes.
* gcc.dg/pr103431.c: New test.
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2021-11-25 21:11 [Bug rtl-optimization/103431] New: [12 Regression] wrong code with -O -fno-tree-bit-ccp -fno-tree-dominator-opts zsojka at seznam dot cz
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2021-11-27 12:02 ` cvs-commit at gcc dot gnu.org
@ 2021-11-27 12:03 ` jakub at gcc dot gnu.org
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From: jakub at gcc dot gnu.org @ 2021-11-27 12:03 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103431
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #8 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed.
^ permalink raw reply [flat|nested] 10+ messages in thread