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UserspaceEmulator: Convert the SUB instruction to inline assembly
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7d41b95071
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1 changed files with 25 additions and 5 deletions
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@ -151,11 +151,31 @@ static typename TypeDoubler<Destination>::type op_xor(SoftCPU& cpu, const Destin
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template<typename Destination, typename Source>
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static typename TypeDoubler<Destination>::type op_sub(SoftCPU& cpu, const Destination& dest, const Source& src)
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{
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u64 result = (u64)dest - (u64)src;
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cpu.set_zf(result == 0);
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cpu.set_sf((result >> (X86::TypeTrivia<Destination>::bits - 1) & 1));
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cpu.set_af((((result ^ (src ^ dest)) & 0x10) >> 4) & 1);
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cpu.set_of((((result ^ dest) & (src ^ dest)) >> (X86::TypeTrivia<Destination>::bits - 1)) & 1);
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Destination result = 0;
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u32 new_flags = 0;
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if constexpr (sizeof(Destination) == 4) {
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asm volatile("subl %%ecx, %%eax\n"
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: "=a"(result)
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: "a"(dest), "c"(src));
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} else if constexpr (sizeof(Destination) == 2) {
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asm volatile("subw %%cx, %%ax\n"
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: "=a"(result)
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: "a"(dest), "c"(src));
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} else if constexpr (sizeof(Destination) == 1) {
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asm volatile("subb %%cl, %%al\n"
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: "=a"(result)
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: "a"(dest), "c"(src));
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} else {
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ASSERT_NOT_REACHED();
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}
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asm volatile(
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"pushf\n"
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"pop %%ebx"
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: "=b"(new_flags));
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cpu.set_flags_oszap(new_flags);
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return result;
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}
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