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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] " carrot at google dot com ` (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 ` carrot at google dot com 2009-09-18 7:57 ` pinskia at gcc dot gnu dot org ` (2 subsequent siblings) 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 ` [Bug middle-end/41396] " carrot at google dot com @ 2009-09-18 7:57 ` pinskia at gcc dot gnu dot org 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 @ 2009-09-18 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] " carrot at google dot com 2009-09-18 7:57 ` pinskia at gcc dot gnu dot org @ 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] " carrot at google dot com 2009-09-18 7:57 ` pinskia at gcc dot gnu dot org 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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