On 22 January 2007 08:19, Yitzchak Scott-Thoennes wrote:
>
> Some people prefer (expr) ? 1 : 0, which looks a lot worse to me than
> !!(expr).
>
Compiles to the exact same thing at -O0 and at -O2, as it happens...
/tmp $ gcc -x c -S -o - -
int foo (int argc)
{
return (argc == 23) ? 1 : 0;
}
int bar (int argc)
{
return !!(argc == 23);
}
.file ""
.text
.globl _foo
.def _foo; .scl 2; .type 32; .endef
_foo:
pushl %ebp
movl %esp, %ebp
cmpl $23, 8(%ebp)
sete %al
movzbl %al, %eax
popl %ebp
ret
.globl _bar
.def _bar; .scl 2; .type 32; .endef
_bar:
pushl %ebp
movl %esp, %ebp
cmpl $23, 8(%ebp)
sete %al
movzbl %al, %eax
popl %ebp
ret
@_______. .
( /"\
||--||(___)
'" '"'---'
/tmp $ gcc -O0 -x c -S -o - -
int foo (int argc)
{
return (argc == 23) ? 1 : 0;
}
int bar (int argc)
{
return !!(argc == 23);
}
.file ""
.text
.globl _foo
.def _foo; .scl 2; .type 32; .endef
_foo:
pushl %ebp
movl %esp, %ebp
cmpl $23, 8(%ebp)
sete %al
movzbl %al, %eax
popl %ebp
ret
.globl _bar
.def _bar; .scl 2; .type 32; .endef
_bar:
pushl %ebp
movl %esp, %ebp
cmpl $23, 8(%ebp)
sete %al
movzbl %al, %eax
popl %ebp
ret
@_______. .
( /"\
||--||(___)
'" '"'---'
/tmp $ gcc -O2 -x c -S -o - -
int foo (int argc)
{
return (argc == 23) ? 1 : 0;
}
int bar (int argc)
{
return !!(argc == 23);
}
.file ""
.text
.p2align 4,,15
.globl _foo
.def _foo; .scl 2; .type 32; .endef
_foo:
pushl %ebp
xorl %eax, %eax
movl %esp, %ebp
cmpl $23, 8(%ebp)
popl %ebp
sete %al
ret
.p2align 4,,15
.globl _bar
.def _bar; .scl 2; .type 32; .endef
_bar:
pushl %ebp
xorl %eax, %eax
movl %esp, %ebp
cmpl $23, 8(%ebp)
popl %ebp
sete %al
ret
@_______. .
( /"\
||--||(___)
'" '"'---'
/tmp $
... so no reason not to choose whichever you like the best.
cheers,
DaveK
--
Can't think of a witty .sigline today....
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