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reimplement LICM::sink to use SSAUpdater instead of PromoteMemToReg.
This leads to much simpler code. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112410 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -45,6 +45,7 @@
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#include "llvm/Analysis/Dominators.h"
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#include "llvm/Analysis/ScalarEvolution.h"
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#include "llvm/Transforms/Utils/PromoteMemToReg.h"
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#include "llvm/Transforms/Utils/SSAUpdater.h"
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#include "llvm/Support/CFG.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/raw_ostream.h"
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@ -477,7 +478,7 @@ void LICM::sink(Instruction &I) {
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// If I has users in unreachable blocks, eliminate.
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// If I is not void type then replaceAllUsesWith undef.
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// This allows ValueHandlers and custom metadata to adjust itself.
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if (!I.getType()->isVoidTy())
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if (!I.use_empty())
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I.replaceAllUsesWith(UndefValue::get(I.getType()));
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I.eraseFromParent();
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} else {
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@ -496,82 +497,41 @@ void LICM::sink(Instruction &I) {
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// If I has users in unreachable blocks, eliminate.
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// If I is not void type then replaceAllUsesWith undef.
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// This allows ValueHandlers and custom metadata to adjust itself.
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if (!I.getType()->isVoidTy())
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if (!I.use_empty())
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I.replaceAllUsesWith(UndefValue::get(I.getType()));
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I.eraseFromParent();
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return;
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}
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// Otherwise, if we have multiple exits, use the PromoteMem2Reg function to
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// do all of the hard work of inserting PHI nodes as necessary. We convert
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// the value into a stack object to get it to do this.
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// Firstly, we create a stack object to hold the value...
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AllocaInst *AI = 0;
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if (!I.getType()->isVoidTy()) {
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AI = new AllocaInst(I.getType(), 0, I.getName(),
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I.getParent()->getParent()->getEntryBlock().begin());
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CurAST->add(AI);
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}
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// Secondly, insert load instructions for each use of the instruction
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// outside of the loop.
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while (!I.use_empty()) {
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Instruction *U = cast<Instruction>(I.use_back());
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// If the user is a PHI Node, we actually have to insert load instructions
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// in all predecessor blocks, not in the PHI block itself!
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if (PHINode *UPN = dyn_cast<PHINode>(U)) {
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// Only insert into each predecessor once, so that we don't have
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// different incoming values from the same block!
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DenseMap<BasicBlock*, Value*> InsertedBlocks;
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for (unsigned i = 0, e = UPN->getNumIncomingValues(); i != e; ++i) {
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if (UPN->getIncomingValue(i) != &I) continue;
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BasicBlock *Pred = UPN->getIncomingBlock(i);
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Value *&PredVal = InsertedBlocks[Pred];
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if (!PredVal) {
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// Insert a new load instruction right before the terminator in
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// the predecessor block.
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PredVal = new LoadInst(AI, "", Pred->getTerminator());
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CurAST->add(cast<LoadInst>(PredVal));
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}
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UPN->setIncomingValue(i, PredVal);
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}
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} else {
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LoadInst *L = new LoadInst(AI, "", U);
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U->replaceUsesOfWith(&I, L);
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CurAST->add(L);
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}
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}
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// Thirdly, insert a copy of the instruction in each exit block of the loop
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// that is dominated by the instruction, storing the result into the memory
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// location. Each exit block is known to only be in the ExitBlocks list once.
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SmallPtrSet<BasicBlock*, 16> InsertedBlocks;
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BasicBlock *InstOrigBB = I.getParent();
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// Otherwise, if we have multiple exits, use the SSAUpdater to do all of the
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// hard work of inserting PHI nodes as necessary.
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SmallVector<PHINode*, 8> NewPHIs;
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SSAUpdater SSA(&NewPHIs);
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if (!I.use_empty())
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SSA.Initialize(&I);
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// Insert a copy of the instruction in each exit block of the loop that is
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// dominated by the instruction. Each exit block is known to only be in the
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// ExitBlocks list once.
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BasicBlock *InstOrigBB = I.getParent();
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unsigned NumInserted = 0;
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for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
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BasicBlock *ExitBlock = ExitBlocks[i];
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if (!isExitBlockDominatedByBlockInLoop(ExitBlock, InstOrigBB))
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continue;
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// Insert the code after the last PHI node...
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// Insert the code after the last PHI node.
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BasicBlock::iterator InsertPt = ExitBlock->getFirstNonPHI();
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// If this is the first exit block processed, just move the original
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// instruction, otherwise clone the original instruction and insert
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// the copy.
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Instruction *New;
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if (NumInserted == 0) {
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I.removeFromParent();
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ExitBlock->getInstList().insert(InsertPt, &I);
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if (NumInserted++ == 0) {
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I.moveBefore(InsertPt);
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New = &I;
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} else {
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New = I.clone();
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@ -581,24 +541,33 @@ void LICM::sink(Instruction &I) {
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ExitBlock->getInstList().insert(InsertPt, New);
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}
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++NumInserted;
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// Now that we have inserted the instruction, store it into the alloca
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if (AI) new StoreInst(New, AI, InsertPt);
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// Now that we have inserted the instruction, inform SSAUpdater.
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if (!I.use_empty())
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SSA.AddAvailableValue(ExitBlock, New);
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}
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// If the instruction doesn't dominate any exit blocks, it must be dead.
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if (NumInserted == 0) {
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CurAST->deleteValue(&I);
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if (!I.use_empty())
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I.replaceAllUsesWith(UndefValue::get(I.getType()));
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I.eraseFromParent();
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return;
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}
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// Finally, promote the fine value to SSA form.
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if (AI) {
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std::vector<AllocaInst*> Allocas;
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Allocas.push_back(AI);
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PromoteMemToReg(Allocas, *DT, *DF, CurAST);
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// Next, rewrite uses of the instruction, inserting PHI nodes as needed.
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for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; ) {
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// Grab the use before incrementing the iterator.
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Use &U = UI.getUse();
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// Increment the iterator before removing the use from the list.
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++UI;
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SSA.RewriteUseAfterInsertions(U);
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}
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// Update CurAST for NewPHIs if I had pointer type.
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if (I.getType()->isPointerTy())
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for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
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CurAST->copyValue(NewPHIs[i], &I);
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}
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/// hoist - When an instruction is found to only use loop invariant operands
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