steam-frame/FEX-Emu--FEX
1
0 Fork 0
mirror of https://github.com/FEX-Emu/FEX.git synced 2026-10-14 13:00:41 +02:00
Code Issues Packages Projects Releases 67 Wiki Activity

OpcodeDispatcher: rework rep cmp

Browse Source 
1. pull flag calculation out of the loop body for perf
2. fully rotate the inner loop to save an instruction per iteration
3. hoist the rcx=0 jump to avoid computing df when rcx=0

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
This commit is contained in:
Alyssa Rosenzweig committed 2024-03-31 19:54:00 -04:00
1 parent a70ea30c02
commit 1a1545da0f
1 file changed
+42 -29
Download Patch File Download Diff File Expand all files Collapse all files
FEXCore/Source/Interface/Core/OpcodeDispatcher.cpp
+42 -29
View File
@@ -3617,26 +3617,24 @@ void OpDispatchBuilder::CMPSOp(OpcodeArgs) {
bool REPE = Op->Flags & FEXCore::X86Tables::DecodeFlags::FLAG_REP_PREFIX;
// read DF once
auto PtrDir = LoadDir(Size);
auto JumpStart = Jump();
// Make sure to start a new block after ending this one
auto LoopStart = CreateNewCodeBlockAfter(GetCurrentBlock());
SetJumpTarget(JumpStart, LoopStart);
SetCurrentCodeBlock(LoopStart);
StartNewBlock();
// If rcx = 0, skip the whole loop.
OrderedNode *Counter = LoadGPRRegister(X86State::REG_RCX);
auto OuterJump = CondJump(Counter, {COND_EQ});
IRPair<IROp_CondJump> InnerJump;
// Can we end the block?
auto CondJump_ = CondJump(Counter, {COND_EQ});
IRPair<IROp_CondJump> InternalCondJump;
auto LoopTail = CreateNewCodeBlockAfter(LoopStart);
SetFalseJumpTarget(CondJump_, LoopTail);
SetCurrentCodeBlock(LoopTail);
// read DF once, outside the loop
auto BeforeLoop = CreateNewCodeBlockAfter(GetCurrentBlock());
SetFalseJumpTarget(OuterJump, BeforeLoop);
SetCurrentCodeBlock(BeforeLoop);
StartNewBlock();
auto PtrDir = LoadDir(Size);
auto JumpIntoLoop = Jump();
// Setup for the loop
auto LoopHeader = CreateNewCodeBlockAfter(GetCurrentBlock());
SetCurrentCodeBlock(LoopHeader);
StartNewBlock();
SetJumpTarget(JumpIntoLoop, LoopHeader);
// Working loop
{
@@ -3651,15 +3649,14 @@ void OpDispatchBuilder::CMPSOp(OpcodeArgs) {
auto Src1 = _LoadMemAutoTSO(GPRClass, Size, Dest_RDI, Size);
auto Src2 = _LoadMem(GPRClass, Size, Dest_RSI, Size);
GenerateFlags_SUB(Op, Src2, Src1);
// Calculate flags early.
CalculateDeferredFlags();
// We'll calculate PF/AF after the loop, so use them as temporaries here.
_StoreRegister(Src1, false, offsetof(FEXCore::Core::CPUState, pf_raw), GPRClass, GPRFixedClass, CTX->GetGPRSize());
_StoreRegister(Src2, false, offsetof(FEXCore::Core::CPUState, af_raw), GPRClass, GPRFixedClass, CTX->GetGPRSize());
OrderedNode *TailCounter = LoadGPRRegister(X86State::REG_RCX);
// Decrement counter
TailCounter = _Sub(OpSize::i64Bit, TailCounter, _Constant(1));
TailCounter = _SubWithFlags(OpSize::i64Bit, TailCounter, _Constant(1));
// Store the counter since we don't have phis
StoreGPRRegister(X86State::REG_RCX, TailCounter);
@@ -3672,21 +3669,37 @@ void OpDispatchBuilder::CMPSOp(OpcodeArgs) {
Dest_RSI = _Add(OpSize::i64Bit, Dest_RSI, PtrDir);
StoreGPRRegister(X86State::REG_RSI, Dest_RSI);
CalculateDeferredFlags();
InternalCondJump = CondJumpNZCV({REPE ? COND_EQ : COND_NEQ});
// If TailCounter != 0, compare sources.
// If TailCounter == 0, set ZF iff that would break.
_CondSubNZCV(OpSize::i64Bit, Src2, Src1, {COND_NEQ}, REPE ? 0 : (1 << 2) /* Z */);
CachedNZCV = nullptr;
NZCVDirty = false;
InnerJump = CondJumpNZCV({REPE ? COND_EQ : COND_NEQ});
// Jump back to the start if we have more work to do
SetTrueJumpTarget(InternalCondJump, LoopStart);
SetTrueJumpTarget(InnerJump, LoopHeader);
}
// Make sure to start a new block after ending this one
auto LoopEnd = CreateNewCodeBlockAfter(LoopTail);
SetTrueJumpTarget(CondJump_, LoopEnd);
SetFalseJumpTarget(InternalCondJump, LoopEnd);
auto LoopEnd = CreateNewCodeBlockAfter(GetCurrentBlock());
SetFalseJumpTarget(InnerJump, LoopEnd);
SetCurrentCodeBlock(LoopEnd);
StartNewBlock();
{
// Grab the sources from the last iteration so we can set flags.
auto Src1 = _LoadRegister(false, offsetof(FEXCore::Core::CPUState, pf_raw), GPRClass, GPRFixedClass, CTX->GetGPRSize());
auto Src2 = _LoadRegister(false, offsetof(FEXCore::Core::CPUState, af_raw), GPRClass, GPRFixedClass, CTX->GetGPRSize());
GenerateFlags_SUB(Op, Src2, Src1);
CalculateDeferredFlags();
}
auto Jump_ = Jump();
auto Exit = CreateNewCodeBlockAfter(LoopEnd);
SetJumpTarget(Jump_, Exit);
SetTrueJumpTarget(OuterJump, Exit);
SetCurrentCodeBlock(Exit);
StartNewBlock();
}
}