>> and don't really object, I'm just curious.
> I guess it's just a matter of taste. I have been known to do it both
> ways. Have you checked to see which generates smaller object code?
Identical object code for both...
(I also tried it with a few other options, including -march=native (which
uses cmov), -O2, reversing the order of the arguments to min(), etc.)
== min.c ==
#include <string.h>
/* Copied from include/linux/kernel.h */
#define min(x, y) ({ \
typeof(x) _min1 = (x); \
typeof(y) _min2 = (y); \
(void) (&_min1 == &_min2); \
_min1 < _min2 ? _min1 : _min2; })
size_t foo(char const *s)
{
size_t len = strlen(s);
if (len > 126)
len = 126;
return len;
}
size_t bar(char const *s)
{
return min(strlen(s), (size_t)126);
}
=== min.s (gcc-4.3 -Os -fomit-frame-pointer) ===
.file "min.c"
.text
.globl bar
.type bar, @function
bar:
pushl %edi
xorl %eax, %eax
subl $4, %esp
orl $-1, %ecx
movl 12(%esp), %edi
repnz scasb
notl %ecx
leal -1(%ecx), %eax
cmpl $126, %eax
jbe .L2
movl $126, %eax
.L2:
popl %edx
popl %edi
ret
.size bar, .-bar
.globl foo
.type foo, @function
foo:
pushl %edi
xorl %eax, %eax
subl $4, %esp
orl $-1, %ecx
movl 12(%esp), %edi
repnz scasb
notl %ecx
leal -1(%ecx), %eax
cmpl $126, %eax
jbe .L5
movl $126, %eax
.L5:
popl %ecx
popl %edi
ret
.size foo, .-foo
.ident "GCC: (Debian 4.3.4-1) 4.3.4"
.section .note.GNU-stack,"",@progbits
=== min.s (gcc-4.4 -Os -fomit-frame-pointer) ===
.file "min.c"
.text
.globl bar
.type bar, @function
bar:
pushl %edi
movl 8(%esp), %edi
xorl %eax, %eax
orl $-1, %ecx
repnz scasb
notl %ecx
leal -1(%ecx), %eax
cmpl $126, %eax
jbe .L2
movl $126, %eax
.L2:
popl %edi
ret
.size bar, .-bar
.globl foo
.type foo, @function
foo:
pushl %edi
movl 8(%esp), %edi
xorl %eax, %eax
orl $-1, %ecx
repnz scasb
notl %ecx
leal -1(%ecx), %eax
cmpl $126, %eax
jbe .L6
movl $126, %eax
.L6:
popl %edi
ret
.size foo, .-foo
.ident "GCC: (Debian 4.4.1-2) 4.4.1"
.section .note.GNU-stack,"",@progbits
=== END ===
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