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UserspaceEmulator: Convert the SUB instruction to inline assembly

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This commit is contained in:
Andreas Kling 2020-07-11 15:52:53 +02:00
parent 7d41b95071
commit 9db588daf1
1 changed files with 25 additions and 5 deletions
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30
DevTools/UserspaceEmulator/SoftCPU.cpp
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@ -151,11 +151,31 @@ static typename TypeDoubler<Destination>::type op_xor(SoftCPU& cpu, const Destin
template<typename Destination, typename Source>
static typename TypeDoubler<Destination>::type op_sub(SoftCPU& cpu, const Destination& dest, const Source& src)
{
u64 result = (u64)dest - (u64)src;
cpu.set_zf(result == 0);
cpu.set_sf((result >> (X86::TypeTrivia<Destination>::bits - 1) & 1));
cpu.set_af((((result ^ (src ^ dest)) & 0x10) >> 4) & 1);
cpu.set_of((((result ^ dest) & (src ^ dest)) >> (X86::TypeTrivia<Destination>::bits - 1)) & 1);
Destination result = 0;
u32 new_flags = 0;
if constexpr (sizeof(Destination) == 4) {
asm volatile("subl %%ecx, %%eax\n"
: "=a"(result)
: "a"(dest), "c"(src));
} else if constexpr (sizeof(Destination) == 2) {
asm volatile("subw %%cx, %%ax\n"
: "=a"(result)
: "a"(dest), "c"(src));
} else if constexpr (sizeof(Destination) == 1) {
asm volatile("subb %%cl, %%al\n"
: "=a"(result)
: "a"(dest), "c"(src));
} else {
ASSERT_NOT_REACHED();
}
asm volatile(
"pushf\n"
"pop %%ebx"
: "=b"(new_flags));
cpu.set_flags_oszap(new_flags);
return result;
}