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: unassig...@gcc.gnu.org
ReportedBy: hjl.to...@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
