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* [Bug tree-optimization/105834] New: Dead Code Elimination Regression at -O2 (trunk vs. 12.1.0)
@ 2022-06-03 13:25 theodort at inf dot ethz.ch
  2022-06-13 12:36 ` [Bug tree-optimization/105834] [13 Regression] " rguenth at gcc dot gnu.org
                   ` (9 more replies)
  0 siblings, 10 replies; 11+ messages in thread
From: theodort at inf dot ethz.ch @ 2022-06-03 13:25 UTC (permalink / raw)
  To: gcc-bugs

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105834

            Bug ID: 105834
           Summary: Dead Code Elimination Regression at -O2 (trunk vs.
                    12.1.0)
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: theodort at inf dot ethz.ch
  Target Milestone: ---

cat case.c
static int a, b;

void foo();

int main() {
    for (int c = 0; c < 2; c = c + (unsigned)3)
        if (a)
            for (;;)
                if (c > 0)
                    b = 0;
    if (b)
        foo();
}

`gcc-1982fe2692b6c3b7f969ffc4edac59f9d4359e91 (trunk) -O2` can not eliminate
`foo` but `gcc-releases/gcc-12.1.0 -O2` can.

`gcc-1982fe2692b6c3b7f969ffc4edac59f9d4359e91 (trunk) -O2 -S -o /dev/stdout
case.c`
--------- OUTPUT ---------
main:
.LFB0:
        .cfi_startproc
        movl    b(%rip), %ecx
        testl   %ecx, %ecx
        jne     .L8
        xorl    %eax, %eax
        ret
.L8:
        pushq   %rax
        .cfi_def_cfa_offset 16
        xorl    %eax, %eax
        call    foo
        xorl    %eax, %eax
        popq    %rdx
        .cfi_def_cfa_offset 8
        ret
---------- END OUTPUT ---------


`gcc-releases/gcc-12.1.0 -O2 -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB0:
        .cfi_startproc
        xorl    %eax, %eax
        ret
---------- END OUTPUT ---------


Bisects to:
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=98e475a8f58ca3ba6e9bd5c9276efce4236f5d26

^ permalink raw reply	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2024-05-21  9:11 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-06-03 13:25 [Bug tree-optimization/105834] New: Dead Code Elimination Regression at -O2 (trunk vs. 12.1.0) theodort at inf dot ethz.ch
2022-06-13 12:36 ` [Bug tree-optimization/105834] [13 Regression] " rguenth at gcc dot gnu.org
2023-02-21 14:23 ` rguenth at gcc dot gnu.org
2023-02-21 22:25 ` pinskia at gcc dot gnu.org
2023-04-08 14:43 ` law at gcc dot gnu.org
2023-04-26  6:56 ` [Bug tree-optimization/105834] [13/14 " rguenth at gcc dot gnu.org
2023-07-13 20:26 ` pinskia at gcc dot gnu.org
2023-07-27  9:23 ` rguenth at gcc dot gnu.org
2023-11-05 22:05 ` tkoenig at gcc dot gnu.org
2023-11-07  8:26 ` [Bug tree-optimization/105834] [13 " rguenth at gcc dot gnu.org
2024-05-21  9:11 ` jakub at gcc dot gnu.org

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