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* [Bug tree-optimization/64718] New: Bad 16-bit bswap replacement
@ 2015-01-21 17:42 aaz@q-fu.com
2015-01-21 19:18 ` [Bug tree-optimization/64718] " hjl.tools at gmail dot com
` (6 more replies)
0 siblings, 7 replies; 8+ messages in thread
From: aaz@q-fu.com @ 2015-01-21 17:42 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64718
Bug ID: 64718
Summary: Bad 16-bit bswap replacement
Product: gcc
Version: 5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: aaz@q-fu.com
Target: i686-pc-linux-gnu
This code is reduced from htons((int)port) on FreeBSD.
The expression gets replaced with a rotation in a 32-bit register
instead of a 16-bit register, so the upper byte is lost.
int swap(int x) {
return (unsigned short)((unsigned short)x << 8 | (unsigned short)x >> 8);
}
gcc -O2 -S swap.c
swap:
movl 4(%esp), %eax
roll $8, %eax # should be %ax
movzwl %ax, %eax
ret
Complete program:
#include <stdio.h>
int swap(int x) {
return (unsigned short)((unsigned short)x << 8 | (unsigned short)x >> 8);
}
int a = 0x1234;
int main() {
int b = 0x1234;
printf("%x -> %x\n", a, swap(a));
printf("%x -> %x\n", b, swap(b));
}
gcc -O2 swap.c && ./a.out
1234 -> 3400
1234 -> 3412
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/64718] Bad 16-bit bswap replacement
2015-01-21 17:42 [Bug tree-optimization/64718] New: Bad 16-bit bswap replacement aaz@q-fu.com
@ 2015-01-21 19:18 ` hjl.tools at gmail dot com
2015-01-21 19:47 ` hjl.tools at gmail dot com
` (5 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: hjl.tools at gmail dot com @ 2015-01-21 19:18 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64718
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Last reconfirmed| |2015-01-21
Target Milestone|--- |5.0
Ever confirmed|0 |1
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/64718] Bad 16-bit bswap replacement
2015-01-21 17:42 [Bug tree-optimization/64718] New: Bad 16-bit bswap replacement aaz@q-fu.com
2015-01-21 19:18 ` [Bug tree-optimization/64718] " hjl.tools at gmail dot com
@ 2015-01-21 19:47 ` hjl.tools at gmail dot com
2015-01-21 19:48 ` hjl.tools at gmail dot com
` (4 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: hjl.tools at gmail dot com @ 2015-01-21 19:47 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64718
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |thomas.preudhomme at arm dot com
--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
It is caused by r219256.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/64718] Bad 16-bit bswap replacement
2015-01-21 17:42 [Bug tree-optimization/64718] New: Bad 16-bit bswap replacement aaz@q-fu.com
2015-01-21 19:18 ` [Bug tree-optimization/64718] " hjl.tools at gmail dot com
2015-01-21 19:47 ` hjl.tools at gmail dot com
@ 2015-01-21 19:48 ` hjl.tools at gmail dot com
2015-01-21 19:51 ` hjl.tools at gmail dot com
` (3 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: hjl.tools at gmail dot com @ 2015-01-21 19:48 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64718
--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
A run-time testcase:
[hjl@gnu-mic-2 gcc-regression]$ cat pr64718.c
int
__attribute__ ((noinline, noclone))
swap(int x)
{
return (unsigned short)((unsigned short)x << 8 | (unsigned short)x >> 8);
}
int a = 0x1234;
int
main()
{
int b = 0x1234;
if (swap (a) != 0x3412)
__builtin_abort ();
if (swap (b) != 0x3412)
__builtin_abort ();
return 0;
}
[hjl@gnu-mic-2 gcc-regression]$
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/64718] Bad 16-bit bswap replacement
2015-01-21 17:42 [Bug tree-optimization/64718] New: Bad 16-bit bswap replacement aaz@q-fu.com
` (2 preceding siblings ...)
2015-01-21 19:48 ` hjl.tools at gmail dot com
@ 2015-01-21 19:51 ` hjl.tools at gmail dot com
2015-01-22 5:56 ` thopre01 at gcc dot gnu.org
` (2 subsequent siblings)
6 siblings, 0 replies; 8+ messages in thread
From: hjl.tools at gmail dot com @ 2015-01-21 19:51 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64718
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target|i686-pc-linux-gnu |x86
Priority|P3 |P1
--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> ---
Also happens on x86-64.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/64718] Bad 16-bit bswap replacement
2015-01-21 17:42 [Bug tree-optimization/64718] New: Bad 16-bit bswap replacement aaz@q-fu.com
` (3 preceding siblings ...)
2015-01-21 19:51 ` hjl.tools at gmail dot com
@ 2015-01-22 5:56 ` thopre01 at gcc dot gnu.org
2015-01-28 10:20 ` thopre01 at gcc dot gnu.org
2015-02-05 10:09 ` [Bug tree-optimization/64718] [5 Regression] " jakub at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2015-01-22 5:56 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64718
thopre01 at gcc dot gnu.org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
--- Comment #4 from thopre01 at gcc dot gnu.org ---
The problem comes from:
bswap_type = TREE_TYPE (src); in bswap_replace when dealing with 16-bit bswap.
I got a fix for that and testing is underway. Thanks for the testcase.
Best regards.
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/64718] Bad 16-bit bswap replacement
2015-01-21 17:42 [Bug tree-optimization/64718] New: Bad 16-bit bswap replacement aaz@q-fu.com
` (4 preceding siblings ...)
2015-01-22 5:56 ` thopre01 at gcc dot gnu.org
@ 2015-01-28 10:20 ` thopre01 at gcc dot gnu.org
2015-02-05 10:09 ` [Bug tree-optimization/64718] [5 Regression] " jakub at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: thopre01 at gcc dot gnu.org @ 2015-01-28 10:20 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64718
--- Comment #5 from Thomas Preud'homme <thopre01 at gcc dot gnu.org> ---
Author: thopre01
Date: Wed Jan 28 10:20:19 2015
New Revision: 220203
URL: https://gcc.gnu.org/viewcvs?rev=220203&root=gcc&view=rev
Log:
2015-01-28 Thomas Preud'homme <thomas.preudhomme@arm.com>
gcc/
PR tree-optimization/64718
* tree-ssa-math-opts.c (pass_optimize_bswap::execute): Make bswap_type
be a 16bit unsigned integer when n->range is 16.
(bswap_replace): Convert src to that type if necessary for all bswap
sizes. Fix rotation right notation in nearby comment. Use bswap_type
set in pass_optimize_bswap::execute ().
gcc/testsuite/
PR tree-optimization/64718
* gcc.c-torture/execute/pr64718.c: New test.
Added:
trunk/gcc/testsuite/gcc.c-torture/execute/pr64718.c
Modified:
trunk/gcc/ChangeLog
trunk/gcc/testsuite/ChangeLog
trunk/gcc/tree-ssa-math-opts.c
^ permalink raw reply [flat|nested] 8+ messages in thread
* [Bug tree-optimization/64718] [5 Regression] Bad 16-bit bswap replacement
2015-01-21 17:42 [Bug tree-optimization/64718] New: Bad 16-bit bswap replacement aaz@q-fu.com
` (5 preceding siblings ...)
2015-01-28 10:20 ` thopre01 at gcc dot gnu.org
@ 2015-02-05 10:09 ` jakub at gcc dot gnu.org
6 siblings, 0 replies; 8+ messages in thread
From: jakub at gcc dot gnu.org @ 2015-02-05 10:09 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64718
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
CC| |jakub at gcc dot gnu.org
Resolution|--- |FIXED
Summary|Bad 16-bit bswap |[5 Regression] Bad 16-bit
|replacement |bswap replacement
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed.
^ permalink raw reply [flat|nested] 8+ messages in thread
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2015-01-21 17:42 [Bug tree-optimization/64718] New: Bad 16-bit bswap replacement aaz@q-fu.com
2015-01-21 19:18 ` [Bug tree-optimization/64718] " hjl.tools at gmail dot com
2015-01-21 19:47 ` hjl.tools at gmail dot com
2015-01-21 19:48 ` hjl.tools at gmail dot com
2015-01-21 19:51 ` hjl.tools at gmail dot com
2015-01-22 5:56 ` thopre01 at gcc dot gnu.org
2015-01-28 10:20 ` thopre01 at gcc dot gnu.org
2015-02-05 10:09 ` [Bug tree-optimization/64718] [5 Regression] " jakub at gcc dot gnu.org
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