[Bug c/34064] New: ARM: missed optimization (conditional store)

[sam at rfc1149 dot net]

The following code

void f(unsigned *_bss_start, unsigned *_bss_end)
{
  unsigned *p;

  for (p = _bss_start; p < _bss_end; p++)
    *p = 0;
}

when compiled with

  arm-elf-gcc -S -o - -fomit-frame-pointer -mcpu=arm7tdmi-s -Os t.c

produces (GCC 4.3.0 20071107)

f:
        mov     r3, #0
        b       .L2
.L3:
        str     r3, [r0], #4
.L2:
        cmp     r0, r1
        bcc     .L3
        bx      lr

It could be further optimized for both space and speed by emitting

f:
        mov     r3, #0
.L1:
        cmp     r0, r1
        strcc   r3, [r0], #4
        bcc     .L1
        bx      lr


-- 
           Summary: ARM: missed optimization (conditional store)
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sam at rfc1149 dot net
 GCC build triplet: arm-elf


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34064