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* [Bug rtl-optimization/51954] New: __int128_t negation can be optimized
@ 2012-01-23 1:43 svfuerst at gmail dot com
2012-01-23 4:00 ` [Bug rtl-optimization/51954] __int128_t (and long long on x86) " pinskia at gcc dot gnu.org
` (9 more replies)
0 siblings, 10 replies; 11+ messages in thread
From: svfuerst at gmail dot com @ 2012-01-23 1:43 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
Bug #: 51954
Summary: __int128_t negation can be optimized
Classification: Unclassified
Product: gcc
Version: 4.7.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: rtl-optimization
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: svfuerst@gmail.com
__int128_t neg(__int128_t x)
{
return -x;
}
Compiles into with -O3 :
mov %rdi, %rax
mov %rsi, %rdx
neg %rax
adc $0x0, %rdx
neg %rdx
retq
Note how the last three instructions before the return are dependent on each
other. This can be slightly improved with slightly more inter-instruction
parallelism:
mov %rdi, %rax
mov %rsi, %rdx
neg %rdx
neg %rax
sbb $0x0, %rdx
retq
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug rtl-optimization/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
@ 2012-01-23 4:00 ` pinskia at gcc dot gnu.org
2021-12-26 22:34 ` [Bug target/51954] " pinskia at gcc dot gnu.org
` (8 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: pinskia at gcc dot gnu.org @ 2012-01-23 4:00 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |x86_64-*-* i?86-*-*
Status|UNCONFIRMED |NEW
Keywords| |missed-optimization
Last reconfirmed| |2012-01-23
Ever Confirmed|0 |1
Summary|__int128_t negation can be |__int128_t (and long long
|optimized |on x86) negation can be
| |optimized
--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-01-23 02:44:13 UTC ---
Confirmed, 64bit long long has a similar improvement for x86:
movl 4(%esp), %eax
movl 8(%esp), %edx
negl %eax
adcl $0, %edx
negl %edx
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
2012-01-23 4:00 ` [Bug rtl-optimization/51954] __int128_t (and long long on x86) " pinskia at gcc dot gnu.org
@ 2021-12-26 22:34 ` pinskia at gcc dot gnu.org
2022-02-21 5:57 ` pinskia at gcc dot gnu.org
` (7 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-12-26 22:34 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
We get this now:
movq %rdi, %rax
movq %rsi, %rdx
negq %rax
adcq $0, %rdx
negq %rdx
ICC produces:
xorl %edx, %edx #3.10
xorl %eax, %eax #3.10
subq %rdi, %rax #3.10
sbbq %rsi, %rdx #3.10
ret #3.10
Which seems even better.
LLVM does produce:
movq %rdi, %rax
xorl %edx, %edx
negq %rax
sbbq %rsi, %rdx
Which basically combines the addcq and negq together and changes one mov into
an exor.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
2012-01-23 4:00 ` [Bug rtl-optimization/51954] __int128_t (and long long on x86) " pinskia at gcc dot gnu.org
2021-12-26 22:34 ` [Bug target/51954] " pinskia at gcc dot gnu.org
@ 2022-02-21 5:57 ` pinskia at gcc dot gnu.org
2022-02-21 6:29 ` crazylht at gmail dot com
` (6 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-02-21 5:57 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |gabravier at gmail dot com
--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 94806 has been marked as a duplicate of this bug. ***
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
` (2 preceding siblings ...)
2022-02-21 5:57 ` pinskia at gcc dot gnu.org
@ 2022-02-21 6:29 ` crazylht at gmail dot com
2022-02-21 6:49 ` crazylht at gmail dot com
` (5 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: crazylht at gmail dot com @ 2022-02-21 6:29 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
--- Comment #4 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to Andrew Pinski from comment #2)
> We get this now:
>
> movq %rdi, %rax
> movq %rsi, %rdx
> negq %rax
> adcq $0, %rdx
> negq %rdx
>
> ICC produces:
> xorl %edx, %edx #3.10
> xorl %eax, %eax #3.10
> subq %rdi, %rax #3.10
> sbbq %rsi, %rdx #3.10
> ret #3.10
>
> Which seems even better.
>
> LLVM does produce:
> movq %rdi, %rax
> xorl %edx, %edx
> negq %rax
> sbbq %rsi, %rdx
>
> Which basically combines the addcq and negq together and changes one mov
> into an exor.
Yes, neg rdx = (0 - rdx) = (0 - (rdx + CF)(last def)) = (sbb 0, rdx)
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
` (3 preceding siblings ...)
2022-02-21 6:29 ` crazylht at gmail dot com
@ 2022-02-21 6:49 ` crazylht at gmail dot com
2022-02-21 7:45 ` ubizjak at gmail dot com
` (4 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: crazylht at gmail dot com @ 2022-02-21 6:49 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
--- Comment #5 from Hongtao.liu <crazylht at gmail dot com> ---
>
> Yes, neg rdx = (0 - rdx) = (0 - (rdx + CF)(last def)) = (sbb 0, rdx)
And we need an extra register for it.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
` (4 preceding siblings ...)
2022-02-21 6:49 ` crazylht at gmail dot com
@ 2022-02-21 7:45 ` ubizjak at gmail dot com
2022-02-21 7:52 ` ubizjak at gmail dot com
` (3 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: ubizjak at gmail dot com @ 2022-02-21 7:45 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
--- Comment #6 from Uroš Bizjak <ubizjak at gmail dot com> ---
Created attachment 52481
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52481&action=edit
Proposed patch
+;; Convert:
+;; mov %esi, %edx
+;; negl %eax
+;; adcl $0, %edx
+;; negl %edx
+;; to:
+;; xorl %edx, %edx
+;; negl %eax
+;; sbbl %esi, %edx
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
` (5 preceding siblings ...)
2022-02-21 7:45 ` ubizjak at gmail dot com
@ 2022-02-21 7:52 ` ubizjak at gmail dot com
2022-02-21 7:57 ` ubizjak at gmail dot com
` (2 subsequent siblings)
9 siblings, 0 replies; 11+ messages in thread
From: ubizjak at gmail dot com @ 2022-02-21 7:52 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
--- Comment #7 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Hongtao.liu from comment #5)
> >
> > Yes, neg rdx = (0 - rdx) = (0 - (rdx + CF)(last def)) = (sbb 0, rdx)
>
> And we need an extra register for it.
The patch in Comment #6 does a conversion, but only when a move is also found.
I have tried to peephole2 with a new temporary, but an additional move to a
temporary besides clearing xor was needed in that case. So the following
testcae:
--cut here--
#ifdef __x86_64__
#define TYPE __int128
#else
#define TYPE long long
#endif
TYPE bar (TYPE x)
{
return -x;
}
--cut here--
when compiled with -O2 -m32 -mregparm=3 leaves unconverted the sequence:
negl %eax
adcl $0, %edx
negl %edx
but generates:
movl 4(%esp), %eax
xorl %edx, %edx
negl %eax
sbbl 8(%esp), %edx
without -mregparm.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
` (6 preceding siblings ...)
2022-02-21 7:52 ` ubizjak at gmail dot com
@ 2022-02-21 7:57 ` ubizjak at gmail dot com
2022-04-29 11:31 ` cvs-commit at gcc dot gnu.org
2022-04-29 11:33 ` ubizjak at gmail dot com
9 siblings, 0 replies; 11+ messages in thread
From: ubizjak at gmail dot com @ 2022-02-21 7:57 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
Uroš Bizjak <ubizjak at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Assignee|unassigned at gcc dot gnu.org |ubizjak at gmail dot com
Target Milestone|--- |13.0
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
` (7 preceding siblings ...)
2022-02-21 7:57 ` ubizjak at gmail dot com
@ 2022-04-29 11:31 ` cvs-commit at gcc dot gnu.org
2022-04-29 11:33 ` ubizjak at gmail dot com
9 siblings, 0 replies; 11+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2022-04-29 11:31 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Uros Bizjak <uros@gcc.gnu.org>:
https://gcc.gnu.org/g:59119253b3133b30114194a04171f9d353b5c7f7
commit r13-38-g59119253b3133b30114194a04171f9d353b5c7f7
Author: Uros Bizjak <ubizjak@gmail.com>
Date: Fri Apr 29 13:27:48 2022 +0200
i386: Optimize double-word negation [PR51954]
Introduce peephole2 pattern to convert from:
mov %esi, %edx
negl %eax
adcl $0, %edx
negl %edx
to:
xorl %edx, %edx
negl %eax
sbbl %esi, %edx
This conversion is profitable only when initial move is found. Otherwise,
additional move to a temporary together with clearing xor is needed.
2022-04-29 Uroš Bizjak <ubizjak@gmail.com>
gcc/ChangeLog:
PR target/51954
* config/i386/i386.md (adcl/neg -> sbb peephole): New peephole2.
gcc/testsuite/ChangeLog:
PR target/51954
* gcc.target/i386/pr51954.c: New test.
^ permalink raw reply [flat|nested] 11+ messages in thread
* [Bug target/51954] __int128_t (and long long on x86) negation can be optimized
2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
` (8 preceding siblings ...)
2022-04-29 11:31 ` cvs-commit at gcc dot gnu.org
@ 2022-04-29 11:33 ` ubizjak at gmail dot com
9 siblings, 0 replies; 11+ messages in thread
From: ubizjak at gmail dot com @ 2022-04-29 11:33 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51954
Uroš Bizjak <ubizjak at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #9 from Uroš Bizjak <ubizjak at gmail dot com> ---
Implemented for gcc-13.
^ permalink raw reply [flat|nested] 11+ messages in thread
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2012-01-23 1:43 [Bug rtl-optimization/51954] New: __int128_t negation can be optimized svfuerst at gmail dot com
2012-01-23 4:00 ` [Bug rtl-optimization/51954] __int128_t (and long long on x86) " pinskia at gcc dot gnu.org
2021-12-26 22:34 ` [Bug target/51954] " pinskia at gcc dot gnu.org
2022-02-21 5:57 ` pinskia at gcc dot gnu.org
2022-02-21 6:29 ` crazylht at gmail dot com
2022-02-21 6:49 ` crazylht at gmail dot com
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