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PPCRec: Reintroduce optimization for BDNZ loops

This commit is contained in:
Exzap 2024-10-25 08:51:22 +02:00
parent e34a273999
commit 5949e620c5
1 changed files with 25 additions and 2 deletions
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27
src/Cafe/HW/Espresso/Recompiler/PPCRecompilerImlGen.cpp
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@ -2930,6 +2930,30 @@ void PPCIMLGen_AssertIfNotLastSegmentInstruction(ppcImlGenContext_t& ppcImlGenCo
cemu_assert_debug(ppcImlGenContext.currentBasicBlock->lastAddress == ppcImlGenContext.ppcAddressOfCurrentInstruction);
}
bool PPCRecompiler_IsBasicBlockATightFiniteLoop(IMLSegment* imlSegment, PPCBasicBlockInfo& basicBlockInfo)
{
// if we detect a finite loop we can skip generating the cycle check
// currently we only check for BDNZ loops since thats reasonably safe to rely on
// however there are other forms of loops that can be classified as finite,
// but detecting those involves analyzing PPC code and we dont have the infrastructure for that (e.g. IML has CheckRegisterUsage but we dont have an equivalent for PPC code)
// base criteria, must jump to beginning of same segment
if (imlSegment->nextSegmentBranchTaken != imlSegment)
return false;
uint32 opcode = *(uint32be*)(memory_base + basicBlockInfo.lastAddress);
if (Espresso::GetPrimaryOpcode(opcode) != Espresso::PrimaryOpcode::BC)
return false;
uint32 BO, BI, BD;
PPC_OPC_TEMPL_B(opcode, BO, BI, BD);
Espresso::BOField boField(BO);
if(!boField.conditionIgnore() || boField.branchAlways())
return false;
if(boField.decrementerIgnore())
return false;
return true;
}
void PPCRecompiler_HandleCycleCheckCount(ppcImlGenContext_t& ppcImlGenContext, PPCBasicBlockInfo& basicBlockInfo)
{
IMLSegment* imlSegment = basicBlockInfo.GetFirstSegmentInChain();
@ -2938,8 +2962,7 @@ void PPCRecompiler_HandleCycleCheckCount(ppcImlGenContext_t& ppcImlGenContext, P
if (basicBlockInfo.branchTarget > basicBlockInfo.startAddress)
return;
// exclude non-infinite tight loops
if (IMLAnalyzer_IsTightFiniteLoop(imlSegment))
if (PPCRecompiler_IsBasicBlockATightFiniteLoop(imlSegment, basicBlockInfo))
return;
// make the segment enterable so execution can return after passing a check