[Bug target/49101] New: [x32] Extra instruction in compare

[hjl.tools at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49101

           Summary: [x32] Extra instruction in compare
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hjl.tools@gmail.com


[hjl@gnu-6 ilp32-41]$ cat foo.c
extern void abort (void);
typedef __SIZE_TYPE__ size_t;
extern size_t strcspn (const char *, const char *);
extern char *strcpy (char *, const char *);

int
main (void)
{
  char *s1 = "hello world";
  char dst[64], *d2;

  strcpy (dst, s1);
  d2 = dst;
  if (strcspn (++d2+5, "") != 5)
    abort();

  return 0;
}
[hjl@gnu-6 ilp32-41]$ make foo.s
/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/ -mx32 -S -o foo.s -mx32 -O 
 foo.c
[hjl@gnu-6 ilp32-41]$ cat foo.s
    .file    "foo.c"
    .text
    .globl    main
    .type    main, @function
main:
.LFB0:
    .cfi_startproc
    subq    $72, %rsp
    .cfi_def_cfa_offset 80
    movl    $1819043176, (%rsp)
    movl    $1870078063, 4(%rsp)
    movl    $6581362, 8(%rsp)
    leaq    6(%rsp), %rdi
    movl    $0, %eax
    movq    $-1, %rcx
    repnz scasb
    notq    %rcx
    cmpl    $6, %ecx
    je    .L2
    call    abort
.L2:
    movl    $0, %eax
    addq    $72, %rsp
    .cfi_def_cfa_offset 8
    ret
    .cfi_endproc
.LFE0:
    .size    main, .-main
    .ident    "GCC: (GNU) 4.7.0 20110521 (experimental)"
    .section    .note.GNU-stack,"",@progbits
[hjl@gnu-6 ilp32-41]$ /export/build/gnu/gcc-x32/build-x86_64-linux/gcc/xgcc
-B/export/build/gnu/gcc-x32/build-x86_64-linux/gcc/ -S -o 64.s -O foo.c
[hjl@gnu-6 ilp32-41]$ diff -up 64.s foo.s
--- 64.s    2011-05-21 06:16:11.260010306 -0700
+++ foo.s    2011-05-21 06:15:38.076996129 -0700
@@ -14,7 +14,8 @@ main:
     movl    $0, %eax
     movq    $-1, %rcx
     repnz scasb
-    cmpq    $-7, %rcx
+    notq    %rcx
+    cmpl    $6, %ecx
     je    .L2
     call    abort
 .L2:
[hjl@gnu-6 ilp32-41]$ 

X32 generates

    notq    %rcx
    cmpl    $6, %ecx

instead of

        cmpq    $-7, %rcx