Hi @ll,
when called with "-O3 -target i386", the compiler fails to
generate properly optimised code (as shown on the right side)
for two of the following (rather trivial) functions:
(see <https://godbolt.org/z/tiwJqX>\)
Especially notice the difference between the signed and unsigned
variants: the latter are properly optimised!
regards
Stefan Kanthak
--- sample3.c ---
__inline
long long Int32x32To64(long x, long y)
{
return (long long) x * y;
}
long Int32x32To64Div32(long a, long b, long c)
{
return Int32x32To64(a, b) / c;
}
Int32x32To64Div32: # @Int32x32To64Div32
push ebp | push ebp
mov ebp, esp | mov ebp, esp
push esi
mov eax, dword ptr [ebp + 12]
mov ecx, dword ptr [ebp + 16] | mov eax, dword ptr [ebp + 16]
imul dword ptr [ebp + 8] | cdq
mov esi, ecx | push edx
sar esi, 31 | push eax
push esi | mov eax, dword ptr [ebp + 12]
push ecx | imul dword ptr [ebp + 8]
push edx | push edx
push eax | push eax
call __divdi3 | call __divdi3
add esp, 16 | add esp, 16
pop esi
pop ebp | pop ebp
ret | ret
long Int32x32To64Rem32(long a, long b, long c)
{
return Int32x32To64(a, b) % c;
}
Int32x32To64Rem32: # @Int32x32To64Rem32
push ebp | push ebp
mov ebp, esp | mov ebp, esp
push esi
mov eax, dword ptr [ebp + 12]
mov ecx, dword ptr [ebp + 16] | mov eax, dword ptr [ebp + 16]
imul dword ptr [ebp + 8] | cdq
mov esi, ecx | push edx
sar esi, 31 | push eax
push esi | mov eax, dword ptr [ebp + 12]
push ecx | imul dword ptr [ebp + 8]
push edx | push edx
push eax | push eax
call __moddi3 | call __modddi3
add esp, 16 | add esp, 16
pop esi
pop ebp | pop ebp
ret | ret
__inline
unsigned long long __fastcall UInt32x32To64(unsigned long x, unsigned long y)
{
return (unsigned long long) x * y;
}
unsigned long UInt32x32To64Div32(unsigned long a, unsigned long b, unsigned long c)
{
return UInt32x32To64(a, b) / c;
}
UInt32x32To64Div32: # @UInt32x32To64Div32
push ebp
mov ebp, esp
mov eax, dword ptr [ebp + 12]
mul dword ptr [ebp + 8]
push 0
push dword ptr [ebp + 16]
push edx
push eax
call __udivdi3
add esp, 16
pop ebp
ret
unsigned long UInt32x32To64Rem32(unsigned long a, unsigned long b, unsigned long c)
{
return UInt32x32To64(a, b) % c;
}
UInt32x32To64Rem32: # @UInt32x32To64Rem32
push ebp
mov ebp, esp
mov eax, dword ptr [ebp + 12]
mul dword ptr [ebp + 8]
push 0
push dword ptr [ebp + 16]
push edx
push eax
call __umoddi3
add esp, 16
pop ebp
ret