[Bug target/40956] New: GCSE opportunity in if statement

[carrot at google dot com]

Compile the following function with options -Os -mthumb -march=armv5te
-frename-registers

int foo(int p, int* q)
{
  if (p!=9)
    *q = 0;
  else
    *(q+1) = 0;
  return 3;
}

GCC generates:

        push    {lr}
        cmp     r0, #9         // D
        beq     .L2
        mov     r3, #0         // A
        str     r3, [r1]
        b       .L3
.L2:
        mov     r0, #0         // B
        str     r0, [r1, #4]   // C
.L3:
        mov     r0, #3
        pop     {pc}

If we replace r0 with r3 in instructions B and C, then A and B will be same. So
we can move the same instruction before the instruction D and reduce 1
instruction.

Is it a gcse opportunity?


-- 
           Summary: GCSE opportunity in if statement
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: carrot at google dot com
 GCC build triplet: i686-linux
  GCC host triplet: i686-linux
GCC target triplet: arm-eabi


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40956