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UserspaceEmulator: Add a fast path for forward REP STOSD

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Same as REP STOSB, except for 32-bit fills instead.
This commit is contained in:
Andreas Kling 2020-11-15 18:07:22 +01:00
parent 102e1d330c
commit 6dab0af9af
3 changed files with 43 additions and 1 deletions
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16
DevTools/UserspaceEmulator/SoftCPU.cpp
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@ -3072,6 +3072,22 @@ void SoftCPU::STOSB(const X86::Instruction& insn)
void SoftCPU::STOSD(const X86::Instruction& insn)
{
if (insn.has_rep_prefix() && !df()) {
// Fast path for 32-bit forward memory fill.
if (m_emulator.mmu().fast_fill_memory32({ es(), destination_index(insn.a32()).value() }, ecx().value(), eax())) {
if (insn.a32()) {
// FIXME: Should an uninitialized ECX taint EDI here?
set_edi({ (u32)(edi().value() + (ecx().value() * sizeof(u32))), edi().shadow() });
set_ecx(shadow_wrap_as_initialized<u32>(0));
} else {
// FIXME: Should an uninitialized CX taint DI here?
set_di({ (u16)(di().value() + (cx().value() * sizeof(u32))), di().shadow() });
set_cx(shadow_wrap_as_initialized<u16>(0));
}
return;
}
}
do_once_or_repeat<false>(insn, [&] {
write_memory32({ es(), destination_index(insn.a32()).value() }, eax());
step_destination_index(insn.a32(), 4);