https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90094
Paul Eggert <eggert at cs dot ucla.edu> changed:
What |Removed |Added
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CC| |eggert at cs dot ucla.edu
--- Comment #3 from Paul Eggert <eggert at cs dot ucla.edu> ---
Slightly better is this equivalent:
unsigned f (long a)
{
return __builtin_sub_overflow (0, a, &a);
}
which gcc -O2 (or -Os) compiles into:
f: xor %eax, %eax
neg %rdi
seto %al
ret
which with GCC is one byte less machine code than the __builtin_sub_overflow(a,
1, &a) approach.
