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https://github.com/ROCm/ROCm.git
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d3956a21f3
Add infrastructure to be able to add and test custom LLVM passes in the backend. This will allow use to apply some low level optimizations and cleanup on LLVM IR. Add a first pass that breaks up phi of struct created by lowering to LLVM. Those can often pessimise the optimizer as it would block optimizations going through phi nodes.
61 lines
2.2 KiB
C++
61 lines
2.2 KiB
C++
//===----------------------------------------------------------------------===//
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/// Implements a trivial pass breaking up 1 level deep structure in phi nodes.
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/// This handles the common case generated by Triton and allow better
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/// optimizations down the compiler pipeline.
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//===----------------------------------------------------------------------===//
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#include "LLVMPasses.h"
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#include "llvm/IR/IRBuilder.h"
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#include "llvm/IR/Instructions.h"
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using namespace llvm;
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static bool processPhiStruct(PHINode *phiNode) {
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StructType *STy = dyn_cast<StructType>(phiNode->getType());
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if (!STy)
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return false;
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IRBuilder<> builder(phiNode);
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unsigned numOperands = phiNode->getNumIncomingValues();
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unsigned numScalarEl = STy->getNumElements();
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Value *newStruct = UndefValue::get(STy);
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builder.SetInsertPoint(phiNode->getParent()->getFirstNonPHI());
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llvm::IRBuilderBase::InsertPoint insertInsertPt = builder.saveIP();
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for (unsigned i = 0; i < numScalarEl; i++) {
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builder.SetInsertPoint(phiNode);
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PHINode *newPhiNode =
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builder.CreatePHI(STy->getElementType(i), numOperands);
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for (unsigned j = 0; j < numOperands; ++j) {
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Value *operand = phiNode->getIncomingValue(j);
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builder.SetInsertPoint(phiNode->getIncomingBlock(j)->getTerminator());
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newPhiNode->addIncoming(builder.CreateExtractValue(operand, i),
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phiNode->getIncomingBlock(j));
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}
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builder.restoreIP(insertInsertPt);
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newStruct = builder.CreateInsertValue(newStruct, newPhiNode, i);
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insertInsertPt = builder.saveIP();
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}
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phiNode->replaceAllUsesWith(newStruct);
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return true;
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}
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static bool runOnFunction(Function &F) {
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bool Changed = false;
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SmallVector<PHINode *> PhiNodes;
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for (BasicBlock &BB : F) {
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for (Instruction &inst : BB) {
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if (PHINode *phiNode = dyn_cast<PHINode>(&inst)) {
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Changed |= processPhiStruct(phiNode);
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continue;
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}
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break;
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}
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}
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return Changed;
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}
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PreservedAnalyses BreakStructPhiNodesPass::run(Function &F,
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FunctionAnalysisManager &AM) {
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bool b = runOnFunction(F);
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return b ? PreservedAnalyses::none() : PreservedAnalyses::all();
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}
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