------- Comment #2 from hjl dot tools at gmail dot com 2009-12-07 18:39 -------
(In reply to comment #1)
> For what it's worth, gcc 3.4.6 generates a clear on the output register, and
> therefore complies with the written ABI.
>
That is true. However, gcc 3.4.6 does:
[...@gnu-26 pr42324]$ cat b1.c
_Bool myfunction(char val);
int
foo (char v)
{
return myfunction (v);
}
[...@gnu-26 pr42324]$ gcc -O2 -S b1.c
[...@gnu-26 pr42324]$ cat b1.s
.file "b1.c"
.text
.p2align 4,,15
.globl foo
.type foo, @function
foo:
.LFB2:
subq $8, %rsp
.LCFI0:
movsbl %dil,%edi
call myfunction
addq $8, %rsp
movzbl %al, %eax
ret
It assumes that _Bool is returned in AL. Gcc 3.4.6 generates:
[...@gnu-26 pr42324]$ cat b2.c
void foo (char, char, char, char, char, char, char, _Bool);
void
myfunction(char val)
{
foo (val, val, val, val, val, val, val, val);
}
[...@gnu-26 pr42324]$ gcc -O2 -S b2.c
[...@gnu-26 pr42324]$ cat b2.s
.file "b2.c"
.text
.p2align 4,,15
.globl myfunction
.type myfunction, @function
myfunction:
.LFB2:
movsbl %dil,%r10d
subq $24, %rsp
.LCFI0:
xorl %eax, %eax
testb %dil, %dil
movl %r10d, %r9d
movl %r10d, %r8d
setne %al
movl %r10d, %ecx
movl %r10d, %edx
movl %r10d, %esi
movl %r10d, %edi
movl %eax, 8(%rsp)
movl %r10d, (%rsp)
call foo
addq $24, %rsp
ret
The upper 32bits of _Bool on stack aren't zeroed.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42324
