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* [Bug target/42879] New: Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2
@ 2010-01-27 0:31 carrot at google dot com
2010-01-27 10:25 ` [Bug target/42879] " rguenth at gcc dot gnu dot org
` (4 more replies)
0 siblings, 5 replies; 6+ messages in thread
From: carrot at google dot com @ 2010-01-27 0:31 UTC (permalink / raw)
To: gcc-bugs
Compile the following c++ code with options -march=armv7-a -mthumb -Os
struct A
{
bool v:1;
};
bool bar();
bool foo(struct A* p)
{
if (p->v)
return true;
return bar();
}
Gcc generates
_Z3fooP1A:
push {r3, lr}
.save {r3, lr}
.LCFI0:
ldrb r3, [r0, #0] @ zero_extendqisi2
tst r3, #1
bne .L3
bl _Z3barv
b .L2
.L3:
movs r0, #1
.L2:
pop {r3, pc}
The "tst r3, #1" is a 32 bit instruction, it can be replaced by a 16 bit
instruction "lsl r3, r3, 31" while still retain the original semantics.
--
Summary: Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: carrot at google dot com
GCC build triplet: i686-linux
GCC host triplet: i686-linux
GCC target triplet: arm-eabi
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42879
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/42879] Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2
2010-01-27 0:31 [Bug target/42879] New: Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2 carrot at google dot com
@ 2010-01-27 10:25 ` rguenth at gcc dot gnu dot org
2010-01-29 23:32 ` ramana at gcc dot gnu dot org
` (3 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2010-01-27 10:25 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from rguenth at gcc dot gnu dot org 2010-01-27 10:25 -------
Could be done in a peephole if there's a scratch available for the destination.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Last reconfirmed|0000-00-00 00:00:00 |2010-01-27 10:25:46
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42879
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/42879] Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2
2010-01-27 0:31 [Bug target/42879] New: Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2 carrot at google dot com
2010-01-27 10:25 ` [Bug target/42879] " rguenth at gcc dot gnu dot org
@ 2010-01-29 23:32 ` ramana at gcc dot gnu dot org
2010-03-19 18:42 ` steven at gcc dot gnu dot org
` (2 subsequent siblings)
4 siblings, 0 replies; 6+ messages in thread
From: ramana at gcc dot gnu dot org @ 2010-01-29 23:32 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from ramana at gcc dot gnu dot org 2010-01-29 23:32 -------
(In reply to comment #1)
> Could be done in a peephole if there's a scratch available for the destination.
>
We already do this for Thumb1 don't we ? Turning on *tlobits_cbranch and the
appropriate bit in arm.c should be enough but GAS doesn't want to assemble lsl
r2,r3, #1 as a 16 bit instruction yet.
cheers
Ramana
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42879
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/42879] Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2
2010-01-27 0:31 [Bug target/42879] New: Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2 carrot at google dot com
2010-01-27 10:25 ` [Bug target/42879] " rguenth at gcc dot gnu dot org
2010-01-29 23:32 ` ramana at gcc dot gnu dot org
@ 2010-03-19 18:42 ` steven at gcc dot gnu dot org
2010-04-24 11:53 ` carrot at google dot com
2010-05-11 3:22 ` carrot at google dot com
4 siblings, 0 replies; 6+ messages in thread
From: steven at gcc dot gnu dot org @ 2010-03-19 18:42 UTC (permalink / raw)
To: gcc-bugs
--
steven at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
OtherBugsDependingO| |16996
nThis| |
Severity|normal |enhancement
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42879
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/42879] Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2
2010-01-27 0:31 [Bug target/42879] New: Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2 carrot at google dot com
` (2 preceding siblings ...)
2010-03-19 18:42 ` steven at gcc dot gnu dot org
@ 2010-04-24 11:53 ` carrot at google dot com
2010-05-11 3:22 ` carrot at google dot com
4 siblings, 0 replies; 6+ messages in thread
From: carrot at google dot com @ 2010-04-24 11:53 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from carrot at google dot com 2010-04-24 11:53 -------
lsls r2,r3, #1 can be assembled to 16 bit.
lsl r2,r3, #1 is 32 bit because only 32 bit encoding can ignore condition
code.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42879
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug target/42879] Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2
2010-01-27 0:31 [Bug target/42879] New: Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2 carrot at google dot com
` (3 preceding siblings ...)
2010-04-24 11:53 ` carrot at google dot com
@ 2010-05-11 3:22 ` carrot at google dot com
4 siblings, 0 replies; 6+ messages in thread
From: carrot at google dot com @ 2010-05-11 3:22 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from carrot at google dot com 2010-05-11 03:21 -------
Fixed by http://gcc.gnu.org/ml/gcc-cvs/2010-05/msg00263.html.
--
carrot at google dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution| |FIXED
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42879
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2010-05-11 3:22 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-01-27 0:31 [Bug target/42879] New: Replace "tst r3, 1" with "lsl r3, r3, 31" in thumb2 carrot at google dot com
2010-01-27 10:25 ` [Bug target/42879] " rguenth at gcc dot gnu dot org
2010-01-29 23:32 ` ramana at gcc dot gnu dot org
2010-03-19 18:42 ` steven at gcc dot gnu dot org
2010-04-24 11:53 ` carrot at google dot com
2010-05-11 3:22 ` carrot at google dot com
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