RGBCube/serenity
1
Fork 0
mirror of https://github.com/RGBCube/serenity synced 2025-05-31 15:48:12 +00:00
Code Issues Activity Actions

UserspaceEmulator: Add a fast path for forward REP STOSB

Browse source 
This is used by memset() so we get a lot of mileage out of optimizing
this instruction.

Note that we currently audit every individual byte accessed separately.
This could be greatly improved by adding a range auditing mechanism to
MallocTracer.
This commit is contained in:
Andreas Kling 2020-11-15 17:54:11 +01:00
parent 92e152f11d
commit 102e1d330c
3 changed files with 45 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

16
DevTools/UserspaceEmulator/SoftCPU.cpp
View file

@ -3048,6 +3048,22 @@ void SoftCPU::STI(const X86::Instruction&) { TODO_INSN(); }
void SoftCPU::STOSB(const X86::Instruction& insn)
{
if (insn.has_rep_prefix() && !df()) {
// Fast path for 8-bit forward memory fill.
if (m_emulator.mmu().fast_fill_memory8({ es(), destination_index(insn.a32()).value() }, ecx().value(), al())) {
if (insn.a32()) {
// FIXME: Should an uninitialized ECX taint EDI here?
set_edi({ (u32)(edi().value() + ecx().value()), 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()), di().shadow() });
set_cx(shadow_wrap_as_initialized<u16>(0));
}
return;
}
}
do_once_or_repeat<false>(insn, [&] {
write_memory8({ es(), destination_index(insn.a32()).value() }, al());
step_destination_index(insn.a32(), 1);