[Bug c/42612] New: [4.4/4.5] post-increment addressing not used

[jon at beniston dot com]

It seems post-increment addressing is not used as often as it could be,
resulting in sub-optimal code. Take this trivial test case:

char * func(char *p)
{
  *p++=0;
  *p++=0;
  *p++=0;
  return p;
}

On ARM, we end up with:

        mov     r2, #0  @ 6
        mov     r3, r0  @ 28
        strb    r2, [r3], #1
        strb    r2, [r0, #1]
        add     r0, r3, #2         
        strb    r2, [r3, #1]
        bx      lr      

The add instruction could be removed if all of the strb instructions used
post-increment addressing.

Problem seems to occur in both 4.4.0 and 4.5.0 latest svn. Also seems to effect
other targets that have post-increment addressing, not just ARM.


-- 
           Summary: [4.4/4.5] post-increment addressing not used
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: jon at beniston dot com
GCC target triplet: arm-elf and others


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42612