https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118958
Jonathan Wakely <redi at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |missed-optimization
Status|WAITING |NEW
--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
using uint8_t = unsigned char;
template<typename T>
constexpr const T&
min(const T& a, const T& b)
{
if (b < a)
return b;
return a;
}
uint8_t func1(uint8_t num)
{
return bool(num);
}
uint8_t func2(uint8_t num)
{
return num < uint8_t(1u) ? uint8_t(0u) : uint8_t(1u);
}
uint8_t func3(uint8_t num)
{
return min(uint8_t(1u), num);
}
uint8_t func4(uint8_t num)
{
return min(num, uint8_t(1u));
}
Clang gives the same code for all four functions, but GCC compiles func4
differently:
func1(unsigned char):
test dil, dil
setne al
ret
func2(unsigned char):
test dil, dil
setne al
ret
func3(unsigned char):
test dil, dil
setne al
ret
func4(unsigned char):
cmp dil, 0
mov eax, 1
cmovbe eax, edi
ret
