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From: "zsojka at seznam dot cz" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/53705] New: wrong code with custom flags - stores to memory are lost Date: Sun, 17 Jun 2012 12:20:00 -0000 [thread overview] Message-ID: <bug-53705-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53705 Bug #: 53705 Summary: wrong code with custom flags - stores to memory are lost Classification: Unclassified Product: gcc Version: 4.8.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: rtl-optimization AssignedTo: unassigned@gcc.gnu.org ReportedBy: zsojka@seznam.cz Created attachment 27640 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27640 reduced testcase (from testsuite/gcc.c-torture/execute/loop-2e.c) GCC 4.3-4.8 fails, while with GCC 4.2, the code is reduced just to return 0. I am not sure if this should be marked as a regression. Compiler output: $ gcc -O2 -fno-omit-frame-pointer -fpeel-loops -fsched2-use-superblocks -fno-tree-loop-optimize -fno-web --param=max-completely-peel-times=256 testcase.c $ ./a.out Aborted Looking at the assembly: ... sub rsp, 320 #, mov rdx, QWORD PTR p[rip] # p.0, p lea rcx, [rbp-320] # q, ... mov QWORD PTR [rcx+240], rdi # *q_19, tmp73 lea rax, [rdx+144] # tmp73, lea rsi, [rdx+148] # tmp73, lea rdi, [rdx+152] # tmp73, lea rdx, [rdx+156] # tmp73, cmp QWORD PTR [rbp-8], rdx # q, tmp73 mov QWORD PTR [rcx+280], rax # *q_19, tmp73 mov QWORD PTR [rcx+248], r8 # *q_19, tmp73 mov QWORD PTR [rcx+256], r9 # *q_19, tmp73 mov QWORD PTR [rcx+264], r10 # *q_19, tmp73 mov QWORD PTR [rcx+272], r11 # *q_19, tmp73 mov QWORD PTR [rcx+288], rsi # *q_19, tmp73 mov QWORD PTR [rcx+296], rdi # *q_19, tmp73 mov QWORD PTR [rcx+304], rdx # *q_19, tmp73 jne .L46 #, ... It seems the dependency between storing to *q++ (esp. q[39]) in foo() and verifying it in main() is lost. Furthermore, it seems q[39] ([rcx+312]) is not stored to at all.
next reply other threads:[~2012-06-17 12:20 UTC|newest] Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-06-17 12:20 zsojka at seznam dot cz [this message] 2012-06-17 15:21 ` [Bug rtl-optimization/53705] " matz at gcc dot gnu.org 2012-06-17 15:36 ` matz at gcc dot gnu.org 2012-06-17 17:43 ` pinskia at gcc dot gnu.org 2013-07-30 13:37 ` amylaar at gcc dot gnu.org
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