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* [Bug middle-end/41396] New: missed space optimization related to basic block reorder
@ 2009-09-18 7:56 carrot at google dot com
2009-09-18 7:57 ` [Bug middle-end/41396] " pinskia at gcc dot gnu dot org
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: carrot at google dot com @ 2009-09-18 7:56 UTC (permalink / raw)
To: gcc-bugs
Compile the attached source code with options -march=armv5te -mthumb -Os, I got
push {r4, lr}
ldr r4, [r0, #8]
ldr r3, [r0, #4]
b .L2
.L7:
ldr r2, [r3, #8]
ldr r1, [r2]
ldr r2, [r3]
add r2, r1, r2
ldr r1, [r3, #4]
ldr r1, [r1]
sub r2, r2, r1
ldr r1, [r3, #12]
cmp r1, #1
beq .L4
cmp r1, #2
bne .L3
b .L12 // C
.L4: // ---------BEGIN BLOCK B
ldr r1, [r0]
neg r1, r1
cmp r2, r1
bge .L3
b .L9 // ----------END BLOCK B
.L12: // ---------------BEGIN BLOCK A-------
ldr r1, [r0]
cmp r2, r1
bgt .L9
.L3:
add r3, r3, #16
.L2:
cmp r3, r4
bcc .L7
mov r0, #0
b .L6 // -----------------END BLOCK A---------
.L9:
mov r0, #1
.L6:
@ sp needed for prologue
pop {r4, pc}
If we change the order of block A and block B, we can remove 2 branch
instructions, inst C and another inst at the end of block B.
Need new basic block reorder algorithm for code size optimization?
--
Summary: missed space optimization related to basic block reorder
Product: gcc
Version: 4.5.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
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=41396
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/41396] missed space optimization related to basic block reorder
2009-09-18 7:56 [Bug middle-end/41396] New: missed space optimization related to basic block reorder carrot at google dot com
2009-09-18 7:57 ` [Bug middle-end/41396] " pinskia at gcc dot gnu dot org
@ 2009-09-18 7:57 ` carrot at google dot com
2009-09-18 8:44 ` rguenth at gcc dot gnu dot org
2009-09-20 21:07 ` pinskia at gcc dot gnu dot org
3 siblings, 0 replies; 5+ messages in thread
From: carrot at google dot com @ 2009-09-18 7:57 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from carrot at google dot com 2009-09-18 07:57 -------
Created an attachment (id=18602)
--> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=18602&action=view)
test case
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41396
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/41396] missed space optimization related to basic block reorder
2009-09-18 7:56 [Bug middle-end/41396] New: missed space optimization related to basic block reorder carrot at google dot com
@ 2009-09-18 7:57 ` pinskia at gcc dot gnu dot org
2009-09-18 7:57 ` carrot at google dot com
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2009-09-18 7:57 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from pinskia at gcc dot gnu dot org 2009-09-18 07:57 -------
yes, currently at -Os basic block reordering is disabled :).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41396
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/41396] missed space optimization related to basic block reorder
2009-09-18 7:56 [Bug middle-end/41396] New: missed space optimization related to basic block reorder carrot at google dot com
2009-09-18 7:57 ` [Bug middle-end/41396] " pinskia at gcc dot gnu dot org
2009-09-18 7:57 ` carrot at google dot com
@ 2009-09-18 8:44 ` rguenth at gcc dot gnu dot org
2009-09-20 21:07 ` pinskia at gcc dot gnu dot org
3 siblings, 0 replies; 5+ messages in thread
From: rguenth at gcc dot gnu dot org @ 2009-09-18 8:44 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from rguenth at gcc dot gnu dot org 2009-09-18 08:44 -------
So, confirmed.
--
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 |2009-09-18 08:44:20
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41396
^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug middle-end/41396] missed space optimization related to basic block reorder
2009-09-18 7:56 [Bug middle-end/41396] New: missed space optimization related to basic block reorder carrot at google dot com
` (2 preceding siblings ...)
2009-09-18 8:44 ` rguenth at gcc dot gnu dot org
@ 2009-09-20 21:07 ` pinskia at gcc dot gnu dot org
3 siblings, 0 replies; 5+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2009-09-20 21:07 UTC (permalink / raw)
To: gcc-bugs
--
pinskia at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
Severity|normal |enhancement
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41396
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2009-09-20 21:07 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2009-09-18 7:56 [Bug middle-end/41396] New: missed space optimization related to basic block reorder carrot at google dot com
2009-09-18 7:57 ` [Bug middle-end/41396] " pinskia at gcc dot gnu dot org
2009-09-18 7:57 ` carrot at google dot com
2009-09-18 8:44 ` rguenth at gcc dot gnu dot org
2009-09-20 21:07 ` pinskia at gcc dot gnu dot org
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