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* [Bug c/35926] New: Pushing / Poping ebx without using it. @ 2008-04-13 17:49 ppelissi at caramail dot com 2008-04-13 17:50 ` [Bug c/35926] " ppelissi at caramail dot com ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: ppelissi at caramail dot com @ 2008-04-13 17:49 UTC (permalink / raw) To: gcc-bugs The following code produces a push and pop of ebx without using it inside: typedef struct toto_s *toto_t; toto_t add (toto_t a, toto_t b) { int64_t tmp = (int64_t)(intptr_t)a + ((int64_t)(intptr_t)b&~1L); return (toto_t)(intptr_t) tmp; } Here is the output of the compiler: gcc version 4.3.0 (GCC) COLLECT_GCC_OPTIONS='-v' '-O3' '-S' '-fomit-frame-pointer' '-save-temps' '-mtune=generic' /usr/local/libexec/gcc/i686-pc-linux-gnu/4.3.0/cc1 -E -quiet -v immediate.c -mtune=generic -fomit-frame-pointer -O3 -fpch-preprocess -o immediate.i ignoring nonexistent directory "/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.0/../../../../i686-pc-linux-gnu/include" #include "..." search starts here: #include <...> search starts here: /usr/local/include /usr/local/lib/gcc/i686-pc-linux-gnu/4.3.0/include /usr/local/lib/gcc/i686-pc-linux-gnu/4.3.0/include-fixed /usr/include End of search list. COLLECT_GCC_OPTIONS='-v' '-O3' '-S' '-fomit-frame-pointer' '-save-temps' '-mtune=generic' /usr/local/libexec/gcc/i686-pc-linux-gnu/4.3.0/cc1 -fpreprocessed immediate.i -quiet -dumpbase immediate.c -mtune=generic -auxbase immediate -O3 -version -fomit-frame-pointer -o immediate.s GNU C (GCC) version 4.3.0 (i686-pc-linux-gnu) compiled by GNU C version 4.3.0, GMP version 4.2.2, MPFR version 2.3.1. warning: GMP header version 4.2.2 differs from library version 4.1.4. GGC heuristics: --param ggc-min-expand=98 --param ggc-min-heapsize=128998 Compiler executable checksum: 6f004a95f08b214d06bfab9d0128e657 COMPILER_PATH=/usr/local/libexec/gcc/i686-pc-linux-gnu/4.3.0/:/usr/local/libexec/gcc/i686-pc-linux-gnu/4.3.0/:/usr/local/libexec/gcc/i686-pc-linux-gnu/:/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.0/:/usr/local/lib/gcc/i686-pc-linux-gnu/ LIBRARY_PATH=/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.0/:/usr/local/lib/gcc/i686-pc-linux-gnu/4.3.0/../../../:/lib/:/usr/lib/ COLLECT_GCC_OPTIONS='-v' '-O3' '-S' '-fomit-frame-pointer' '-save-temps' '-mtune=generic' [pphd@localhost to-do]$ cat immediate.s .file "immediate.c" .text .p2align 4,,15 .globl add .type add, @function add: pushl %ebx movl 12(%esp), %eax movl 8(%esp), %ecx popl %ebx andl $-2, %eax addl %ecx, %eax ret .size add, .-add .ident "GCC: (GNU) 4.3.0" .section .note.GNU-stack,"",@progbits I can reproduce this problem for GCC 4.1.2 and GCC 4.2.2 too. -- Summary: Pushing / Poping ebx without using it. Product: gcc Version: 4.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: ppelissi at caramail dot com GCC build triplet: i686-pc-linux-gnu GCC host triplet: i686-pc-linux-gnu GCC target triplet: i686-pc-linux-gnu http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35926 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c/35926] Pushing / Poping ebx without using it. 2008-04-13 17:49 [Bug c/35926] New: Pushing / Poping ebx without using it ppelissi at caramail dot com @ 2008-04-13 17:50 ` ppelissi at caramail dot com 2008-04-14 9:19 ` [Bug target/35926] " rguenth at gcc dot gnu dot org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: ppelissi at caramail dot com @ 2008-04-13 17:50 UTC (permalink / raw) To: gcc-bugs ------- Comment #1 from ppelissi at caramail dot com 2008-04-13 17:49 ------- Created an attachment (id=15473) --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15473&action=view) preprocessed sources -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35926 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug target/35926] Pushing / Poping ebx without using it. 2008-04-13 17:49 [Bug c/35926] New: Pushing / Poping ebx without using it ppelissi at caramail dot com 2008-04-13 17:50 ` [Bug c/35926] " ppelissi at caramail dot com @ 2008-04-14 9:19 ` rguenth at gcc dot gnu dot org 2008-04-14 11:13 ` ubizjak at gmail dot com 2008-12-28 7:00 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: rguenth at gcc dot gnu dot org @ 2008-04-14 9:19 UTC (permalink / raw) To: gcc-bugs ------- Comment #2 from rguenth at gcc dot gnu dot org 2008-04-14 09:18 ------- This is setting up the frame pointer which is needed for unwinding/debugging on some targets. You can use -fomit-frame-pointer to avoid this. -- rguenth at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution| |INVALID http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35926 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug target/35926] Pushing / Poping ebx without using it. 2008-04-13 17:49 [Bug c/35926] New: Pushing / Poping ebx without using it ppelissi at caramail dot com 2008-04-13 17:50 ` [Bug c/35926] " ppelissi at caramail dot com 2008-04-14 9:19 ` [Bug target/35926] " rguenth at gcc dot gnu dot org @ 2008-04-14 11:13 ` ubizjak at gmail dot com 2008-12-28 7:00 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: ubizjak at gmail dot com @ 2008-04-14 11:13 UTC (permalink / raw) To: gcc-bugs ------- Comment #3 from ubizjak at gmail dot com 2008-04-14 11:12 ------- (In reply to comment #2) > This is setting up the frame pointer which is needed for unwinding/debugging > on some targets. You can use -fomit-frame-pointer to avoid this. No, -fomit-frame-pointer uses %ebp. %ebx is marked as used due to long long value in %ecx/%ebx. For some reason, %ebx is still marked as live when function prologue and epilogue are constructed. -- ubizjak at gmail dot com changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |UNCONFIRMED Resolution|INVALID | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35926 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug target/35926] Pushing / Poping ebx without using it. 2008-04-13 17:49 [Bug c/35926] New: Pushing / Poping ebx without using it ppelissi at caramail dot com ` (2 preceding siblings ...) 2008-04-14 11:13 ` ubizjak at gmail dot com @ 2008-12-28 7:00 ` pinskia at gcc dot gnu dot org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu dot org @ 2008-12-28 7:00 UTC (permalink / raw) To: gcc-bugs ------- Comment #4 from pinskia at gcc dot gnu dot org 2008-12-28 06:57 ------- Confirmed, still happens even after IRA. ebx is still being marked as being used even though the RA does not use it. -- pinskia at gcc dot gnu dot org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Ever Confirmed|0 |1 GCC build triplet|i686-pc-linux-gnu | GCC host triplet|i686-pc-linux-gnu | GCC target triplet|i686-pc-linux-gnu |i?86-*-* Keywords| |missed-optimization, ra Last reconfirmed|0000-00-00 00:00:00 |2008-12-28 06:57:47 date| | http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35926 ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2008-12-28 7:00 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2008-04-13 17:49 [Bug c/35926] New: Pushing / Poping ebx without using it ppelissi at caramail dot com 2008-04-13 17:50 ` [Bug c/35926] " ppelissi at caramail dot com 2008-04-14 9:19 ` [Bug target/35926] " rguenth at gcc dot gnu dot org 2008-04-14 11:13 ` ubizjak at gmail dot com 2008-12-28 7:00 ` pinskia at gcc dot gnu dot org
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