[Bug middle-end/30026] New: useless stack movement

[acahalan at gmail dot com]

There is no reason to be moving %esp in this function.

$ cat cc.c
typedef unsigned long size_t;
extern void *memcpy (void *__restrict, const void *__restrict, size_t);
char *foo1(char*buf){
  short tmp2;
  int tmp4;
  *buf++ = 42;
  tmp2=0xfeed;
  memcpy(buf,&tmp2,2);
  buf += 2;
  tmp4 = 0x12345678;
  memcpy(buf,&tmp4,4);
  buf += 4;
  tmp4 = 0x12345678;
  memcpy(buf,&tmp4,4);
  buf += 4;
  return buf;
}
$ gcc -m32 -fomit-frame-pointer -mregparm=3 -O2 -S cc.c
$ cat cc.s
        .file   "cc.c"
        .text
        .p2align 4,,15
.globl foo1
        .type   foo1, @function
foo1:
        subl    $16, %esp
        movb    $42, (%eax)
        movw    $-275, 1(%eax)
        movl    $305419896, 3(%eax)
        movl    $305419896, 7(%eax)
        addl    $11, %eax
        addl    $16, %esp
        ret
        .size   foo1, .-foo1
        .ident  "GCC: (GNU) 4.1.1 20060828 (Red Hat 4.1.1-20)"
        .section        .note.GNU-stack,"",@progbits
$


-- 
           Summary: useless stack movement
           Product: gcc
           Version: 4.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: acahalan at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30026