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* [Bug middle-end/38126] suboptimal code for (a && b || !a && !b)
[not found] <bug-38126-4@http.gcc.gnu.org/bugzilla/>
@ 2012-02-01 22:38 ` pinskia at gcc dot gnu.org
2012-02-02 5:26 ` svfuerst at gmail dot com
` (4 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2012-02-01 22:38 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38126
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Status|UNCONFIRMED |NEW
Last reconfirmed| |2012-02-01
Ever Confirmed|0 |1
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> 2012-02-01 22:37:56 UTC ---
Confirmed.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/38126] suboptimal code for (a && b || !a && !b)
[not found] <bug-38126-4@http.gcc.gnu.org/bugzilla/>
2012-02-01 22:38 ` [Bug middle-end/38126] suboptimal code for (a && b || !a && !b) pinskia at gcc dot gnu.org
@ 2012-02-02 5:26 ` svfuerst at gmail dot com
2012-02-02 6:12 ` svfuerst at gmail dot com
` (3 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: svfuerst at gmail dot com @ 2012-02-02 5:26 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38126
Steven Fuerst <svfuerst at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |svfuerst at gmail dot com
--- Comment #3 from Steven Fuerst <svfuerst at gmail dot com> 2012-02-02 05:25:34 UTC ---
For the first pair of functions, this is even faster:
neg %rdi
sbb %eax, %eax
neg %rsi
adc $1, %eax
and $1, %eax
retq
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/38126] suboptimal code for (a && b || !a && !b)
[not found] <bug-38126-4@http.gcc.gnu.org/bugzilla/>
2012-02-01 22:38 ` [Bug middle-end/38126] suboptimal code for (a && b || !a && !b) pinskia at gcc dot gnu.org
2012-02-02 5:26 ` svfuerst at gmail dot com
@ 2012-02-02 6:12 ` svfuerst at gmail dot com
2021-06-03 2:48 ` pinskia at gcc dot gnu.org
` (2 subsequent siblings)
5 siblings, 0 replies; 8+ messages in thread
From: svfuerst at gmail dot com @ 2012-02-02 6:12 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38126
--- Comment #4 from Steven Fuerst <svfuerst at gmail dot com> 2012-02-02 06:11:27 UTC ---
Two more cases for simple boolean logic optimizations.
gcc-4.7 produces with -O3 for
int test_and(long long x, long long y)
{
return x && y;
}
test %rsi, %rsi
setne %dl
xor %eax, %eax
test %rdi, %rdi
setne %al
and %edx, %eax
retq
Whereas this is faster:
neg %rdi
sbb %rdi, %rdi
xor %eax, %eax
and %rsi, %rdi
setne %al
retq
Also
int test_other(long long x, long long y)
{
return !x && y; /* or !(x || !y) */
}
gives
test %rsi,%rsi
setne %dl
xor %eax,%eax
test %rdi,%rdi
sete %al
and %edx,%eax
retq
when
sub $1, %rsi
sbb %rsi, %rsi
xor %eax, %eax
or %rdi, %rsi
sete %al
retq
is faster.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/38126] suboptimal code for (a && b || !a && !b)
[not found] <bug-38126-4@http.gcc.gnu.org/bugzilla/>
` (2 preceding siblings ...)
2012-02-02 6:12 ` svfuerst at gmail dot com
@ 2021-06-03 2:48 ` pinskia at gcc dot gnu.org
2022-11-26 20:40 ` [Bug target/38126] " pinskia at gcc dot gnu.org
2022-12-19 20:57 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2021-06-03 2:48 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38126
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
For the original testcase with GCC 7, we get the same(similar enough) code gen
for both functions now.
foo:
.LFB0:
.cfi_startproc
testq %rdi, %rdi
setne %al
testq %rsi, %rsi
sete %dl
xorl %edx, %eax
movzbl %al, %eax
ret
bar:
.LFB1:
.cfi_startproc
testq %rdi, %rdi
sete %al
testq %rsi, %rsi
setne %dl
xorl %edx, %eax
movzbl %al, %eax
ret
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug target/38126] suboptimal code for (a && b || !a && !b)
[not found] <bug-38126-4@http.gcc.gnu.org/bugzilla/>
` (3 preceding siblings ...)
2021-06-03 2:48 ` pinskia at gcc dot gnu.org
@ 2022-11-26 20:40 ` pinskia at gcc dot gnu.org
2022-12-19 20:57 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-11-26 20:40 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38126
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target| |x86_64
Component|middle-end |target
Target Milestone|--- |13.0
--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #1)
> Code involving bool variables is similarly suboptimal:
The bool part was fixed for GCC 13 by r13-1779-g375668e0508fbe .
The rest is a target issue dealing with using sbb more.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug target/38126] suboptimal code for (a && b || !a && !b)
[not found] <bug-38126-4@http.gcc.gnu.org/bugzilla/>
` (4 preceding siblings ...)
2022-11-26 20:40 ` [Bug target/38126] " pinskia at gcc dot gnu.org
@ 2022-12-19 20:57 ` pinskia at gcc dot gnu.org
5 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu.org @ 2022-12-19 20:57 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38126
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|13.0 |---
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug c/38126] New: suboptimal code for (a && b || !a && !b)
@ 2008-11-15 0:07 sebor at roguewave dot com
2008-11-15 0:11 ` [Bug middle-end/38126] " pinskia at gcc dot gnu dot org
2009-09-12 23:33 ` msebor at gmail dot com
0 siblings, 2 replies; 8+ messages in thread
From: sebor at roguewave dot com @ 2008-11-15 0:07 UTC (permalink / raw)
To: gcc-bugs
I would expect gcc to generate comparable code for both functions below, or
perhaps even better code for foo() than for bar() since the code in foo() is
likely to be more common than the equivalent code in bar(). However, the code
produced for foo() is suboptimal in comparison to the code for bar(). In my
timings on x86 with gcc 4.3.0 at -O2, foo() appears to run about 5% slower than
bar().
$ cat t.c && gcc -S -O2 t.c && cat t.s
int foo (int *a, int *b) { return a && b || !a && !b; }
int bar (int *a, int *b) { return !!a == !!b; }
.file "t.c"
.text
.p2align 4,,15
.globl foo
.type foo, @function
foo:
.LFB2:
testq %rdi, %rdi
je .L2
testq %rsi, %rsi
movl $1, %eax
je .L2
rep
ret
.p2align 4,,10
.p2align 3
.L2:
testq %rdi, %rdi
sete %al
testq %rsi, %rsi
sete %dl
andl %edx, %eax
movzbl %al, %eax
ret
.LFE2:
.size foo, .-foo
.p2align 4,,15
.globl bar
.type bar, @function
bar:
.LFB3:
testq %rdi, %rdi
sete %al
testq %rsi, %rsi
setne %dl
xorl %edx, %eax
movzbl %al, %eax
ret
.LFE3:
.size bar, .-bar
.section .eh_frame,"a",@progbits
.Lframe1:
.long .LECIE1-.LSCIE1
.LSCIE1:
.long 0x0
.byte 0x1
.string "zR"
.uleb128 0x1
.sleb128 -8
.byte 0x10
.uleb128 0x1
.byte 0x3
.byte 0xc
.uleb128 0x7
.uleb128 0x8
.byte 0x90
.uleb128 0x1
.align 8
.LECIE1:
.LSFDE1:
.long .LEFDE1-.LASFDE1
.LASFDE1:
.long .LASFDE1-.Lframe1
.long .LFB2
.long .LFE2-.LFB2
.uleb128 0x0
.align 8
.LEFDE1:
.LSFDE3:
.long .LEFDE3-.LASFDE3
.LASFDE3:
.long .LASFDE3-.Lframe1
.long .LFB3
.long .LFE3-.LFB3
.uleb128 0x0
.align 8
.LEFDE3:
.ident "GCC: (GNU) 4.3.0 20080428 (Red Hat 4.3.0-8)"
.section .note.GNU-stack,"",@progbits
--
Summary: suboptimal code for (a && b || !a && !b)
Product: gcc
Version: 4.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: sebor at roguewave dot com
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38126
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/38126] suboptimal code for (a && b || !a && !b)
2008-11-15 0:07 [Bug c/38126] New: " sebor at roguewave dot com
@ 2008-11-15 0:11 ` pinskia at gcc dot gnu dot org
2009-09-12 23:33 ` msebor at gmail dot com
1 sibling, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2008-11-15 0:11 UTC (permalink / raw)
To: gcc-bugs
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
Component|c |middle-end
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38126
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug middle-end/38126] suboptimal code for (a && b || !a && !b)
2008-11-15 0:07 [Bug c/38126] New: " sebor at roguewave dot com
2008-11-15 0:11 ` [Bug middle-end/38126] " pinskia at gcc dot gnu dot org
@ 2009-09-12 23:33 ` msebor at gmail dot com
1 sibling, 0 replies; 8+ messages in thread
From: msebor at gmail dot com @ 2009-09-12 23:33 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from msebor at gmail dot com 2009-09-12 23:33 -------
Code involving bool variables is similarly suboptimal:
$ cat t.cpp && gcc -O2 -S t.cpp && cat t.s
bool foo (bool a, bool b) {
return a && b || !a && !b;
}
bool bar (bool a, bool b) {
return a == b;
}
.file "t.cpp"
.text
.p2align 4,,15
.globl _Z3foobb
.type _Z3foobb, @function
_Z3foobb:
.LFB0:
.cfi_startproc
.cfi_personality 0x3,__gxx_personality_v0
movl %esi, %edx
movl %esi, %eax
xorl $1, %edx
testb %dil, %dil
cmove %edx, %eax
ret
.cfi_endproc
.LFE0:
.size _Z3foobb, .-_Z3foobb
.p2align 4,,15
.globl _Z3barbb
.type _Z3barbb, @function
_Z3barbb:
.LFB1:
.cfi_startproc
.cfi_personality 0x3,__gxx_personality_v0
cmpb %dil, %sil
sete %al
ret
.cfi_endproc
.LFE1:
.size _Z3barbb, .-_Z3barbb
.ident "GCC: (GNU) 4.4.1 20090725 (Red Hat 4.4.1-2)"
.section .note.GNU-stack,"",@progbits
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38126
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-12-19 20:57 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
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[not found] <bug-38126-4@http.gcc.gnu.org/bugzilla/>
2012-02-01 22:38 ` [Bug middle-end/38126] suboptimal code for (a && b || !a && !b) pinskia at gcc dot gnu.org
2012-02-02 5:26 ` svfuerst at gmail dot com
2012-02-02 6:12 ` svfuerst at gmail dot com
2021-06-03 2:48 ` pinskia at gcc dot gnu.org
2022-11-26 20:40 ` [Bug target/38126] " pinskia at gcc dot gnu.org
2022-12-19 20:57 ` pinskia at gcc dot gnu.org
2008-11-15 0:07 [Bug c/38126] New: " sebor at roguewave dot com
2008-11-15 0:11 ` [Bug middle-end/38126] " pinskia at gcc dot gnu dot org
2009-09-12 23:33 ` msebor at gmail dot com
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