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From: "mikulas at artax dot karlin dot mff dot cuni dot cz" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug regression/40667] New: Performance regression: stack frames are generated even with -fomit-frame-pointer Date: Tue, 07 Jul 2009 02:25:00 -0000 [thread overview] Message-ID: <bug-40667-1600@http.gcc.gnu.org/bugzilla/> (raw) This is performance regression from 4.3 (which was better). On i386, when -O2 -fomit-frame-pointer -mpreferred-stack-boundary=2 is used, and function operates with long long values, stack frame is generated, although it doesn't have to be. Example: int f(long long x); int g(long long x) { f(x); return 0; } Generated code: .text .p2align 4,,15 .globl g .type g, @function g: pushl %ebp movl %esp, %ebp subl $8, %esp movl 8(%ebp), %eax movl 12(%ebp), %edx movl %eax, (%esp) movl %edx, 4(%esp) call f xorl %eax, %eax leave ret .size g, .-g Gcc 4.3 didn't generate stack frame in this case. On i386, spurious stack frame is especially bad because there are few registers and one register is lost for the stack frame. One my program doing heavy 64-bit math shows almost 1% code size increase because of these unneeded frames. -- Summary: Performance regression: stack frames are generated even with -fomit-frame-pointer Product: gcc Version: 4.4.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: regression AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: mikulas at artax dot karlin dot mff dot cuni dot cz 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=40667
next reply other threads:[~2009-07-07 2:25 UTC|newest] Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top 2009-07-07 2:25 mikulas at artax dot karlin dot mff dot cuni dot cz [this message] 2009-07-07 9:07 ` [Bug regression/40667] " rguenth at gcc dot gnu dot org 2009-07-07 14:41 ` hjl dot tools at gmail dot com 2009-07-07 16:48 ` mikulas at artax dot karlin dot mff dot cuni dot cz 2009-07-09 9:05 ` [Bug rtl-optimization/40667] [4.4/4.5 Regression] " ubizjak at gmail dot com 2009-07-09 9:20 ` ubizjak at gmail dot com 2009-07-09 11:45 ` jakub at gcc dot gnu dot org 2009-07-09 12:05 ` jakub at gcc dot gnu dot org 2009-07-09 12:56 ` jakub at gcc dot gnu dot org 2009-07-09 13:25 ` jakub at gcc dot gnu dot org 2009-07-09 13:58 ` hjl dot tools at gmail dot com 2009-07-09 15:49 ` rguenth at gcc dot gnu dot org 2009-07-09 16:24 ` jakub at gcc dot gnu dot org 2009-07-09 16:35 ` hjl dot tools at gmail dot com 2009-07-11 17:40 ` jakub at gcc dot gnu dot org 2009-07-11 19:06 ` jakub at gcc dot gnu dot org 2009-07-11 19:07 ` jakub at gcc dot gnu dot org 2009-07-23 11:13 ` mikulas at artax dot karlin dot mff dot cuni dot cz 2009-07-23 11:18 ` mikulas at artax dot karlin dot mff dot cuni dot cz 2009-07-23 11:36 ` jakub at gcc dot gnu dot org 2009-07-23 12:17 ` mikulas at artax dot karlin dot mff dot cuni dot cz 2009-07-23 12:34 ` jakub at gcc dot gnu dot org 2009-07-23 13:28 ` mikulas at artax dot karlin dot mff dot cuni dot cz 2009-08-08 10:41 ` mikulas at artax dot karlin dot mff dot cuni dot cz 2009-08-08 11:45 ` hjl dot tools at gmail dot com 2009-08-08 14:15 ` mikulas at artax dot karlin dot mff dot cuni dot cz 2009-08-11 21:01 ` mikulas at artax dot karlin dot mff dot cuni dot cz 2010-02-15 4:23 ` [Bug target/40667] " pinskia at gcc dot gnu dot org 2010-02-15 10:34 ` mikulas at artax dot karlin dot mff dot cuni dot cz 2010-06-29 21:17 ` [Bug target/40667] [4.4/4.5/4.6 " pinskia at gcc dot gnu dot org
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