| Issue |
131685
|
| Summary |
Does not emit __udivmoddi4
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
purplesyringa
|
Somewhat similarly to #46350, the following code is compiled suboptimally on i686 (and probably other 32-bit architectures):
```c
typedef unsigned long long u64;
struct div_mod {
u64 div, mod;
};
struct div_mod div_mod(u64 x, u64 y) {
struct div_mod out = {x / y, x % y};
return out;
}
```
GCC compiles this to:
```x86asm
div_mod:
push ebx
sub esp, 24
mov ebx, DWORD PTR [esp+32]
lea eax, [esp+8]
sub esp, 12
push eax
push DWORD PTR [esp+64]
push DWORD PTR [esp+64]
push DWORD PTR [esp+64]
push DWORD PTR [esp+64]
call __udivmoddi4
movq xmm0, QWORD PTR [esp+40]
mov DWORD PTR [ebx], eax
mov eax, ebx
mov DWORD PTR [ebx+4], edx
movq QWORD PTR [ebx+8], xmm0
add esp, 56
pop ebx
ret 4
```
But Clang emits
```x86asm
div_mod:
push ebp
push ebx
push edi
push esi
sub esp, 12
call .L0$pb
.L0$pb:
pop ebx
.Ltmp0:
add ebx, offset _GLOBAL_OFFSET_TABLE_+(.Ltmp0-.L0$pb)
mov ebp, dword ptr [esp + 36]
mov esi, dword ptr [esp + 48]
push esi
push dword ptr [esp + 48]
push dword ptr [esp + 48]
push ebp
call __udivdi3@PLT
add esp, 16
mov ecx, eax
mov edi, edx
imul esi, eax
mov ebx, dword ptr [esp + 44]
mul ebx
add edx, esi
mov esi, dword ptr [esp + 32]
mov dword ptr [esi + 4], edi
imul edi, ebx
add edi, edx
sub ebp, eax
mov edx, dword ptr [esp + 40]
sbb edx, edi
mov eax, esi
mov dword ptr [esi], ecx
mov dword ptr [esi + 8], ebp
mov dword ptr [esi + 12], edx
add esp, 12
pop esi
pop edi
pop ebx
pop ebp
ret 4
```
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