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From: "christian.prochaska@genode-labs.com" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/66090] New: Wrong loop code generation with -O2 on ARM Date: Sun, 10 May 2015 02:28:00 -0000 [thread overview] Message-ID: <bug-66090-4@http.gcc.gnu.org/bugzilla/> (raw) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66090 Bug ID: 66090 Summary: Wrong loop code generation with -O2 on ARM Product: gcc Version: 4.9.2 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: christian.prochaska@genode-labs.com Target Milestone: --- test.c: void func() { unsigned int i; unsigned int *ptr = (unsigned int*)0xfffff000; for (i = 0; i < 1024; i++) *(ptr++) = 0; } Compiled with GCC 4.9.2 from the Xubuntu 15.04 repository: arm-linux-gnueabihf-gcc-4.9 -marm -c -O2 test.c Generated code: 00000000 <func>: func(): 0: e3a03a0f mov r3, #61440 ; 0xf000 4: e3a02000 mov r2, #0 8: e34f3fff movt r3, #65535 ; 0xffff c: e4832004 str r2, [r3], #4 10: eafffffd b c <func+0xc> There is no check of the loop exit condition. When compiling with -O1, it is there: 00000000 <func>: func(): 0: e3a03a0f mov r3, #61440 ; 0xf000 4: e34f3fff movt r3, #65535 ; 0xffff 8: e3a02000 mov r2, #0 c: e4832004 str r2, [r3], #4 10: e3530000 cmp r3, #0 14: 1afffffc bne c <func+0xc> 18: e12fff1e bx lr The problem does not occur with GCC 4.8.4.
next reply other threads:[~2015-05-10 2:28 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2015-05-10 2:28 christian.prochaska@genode-labs.com [this message] 2015-05-10 11:09 ` [Bug c/66090] " kugan at gcc dot gnu.org 2015-05-10 21:43 ` pinskia at gcc dot gnu.org 2015-05-12 19:46 ` rearnsha at gcc dot gnu.org 2015-05-13 8:54 ` rguenth at gcc dot gnu.org 2015-05-13 8:54 ` rguenth at gcc dot gnu.org 2015-05-13 15:20 ` joseph at codesourcery dot com 2015-06-02 9:02 ` wad at infinet dot ru 2015-06-02 9:07 ` ktkachov at gcc dot gnu.org 2015-06-02 9:13 ` pinskia at gcc dot gnu.org 2015-06-02 9:45 ` wad at infinet dot ru 2015-06-22 18:01 ` mpolacek at gcc dot gnu.org
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