forked from OSchip/llvm-project
[LoopDeletion] Teach LoopDeletion to preserve MemorySSA if available.
If MemorySSA analysis is analysis, LoopDeletion now preserves it.
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eec36909c1
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efb130fc93
llvm
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@ -41,6 +41,7 @@ class DataLayout;
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class Loop;
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class LoopInfo;
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class MemoryAccess;
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class MemorySSA;
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class MemorySSAUpdater;
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class OptimizationRemarkEmitter;
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class PredicatedScalarEvolution;
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@ -144,12 +145,12 @@ bool hoistRegion(DomTreeNode *, AliasAnalysis *, LoopInfo *, DominatorTree *,
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/// - The loop needs to have a Preheader
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/// - A unique dedicated exit block must exist
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///
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/// This also updates the relevant analysis information in \p DT, \p SE, and \p
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/// LI if pointers to those are provided.
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/// This also updates the relevant analysis information in \p DT, \p SE, \p LI
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/// and \p MSSA if pointers to those are provided.
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/// It also updates the loop PM if an updater struct is provided.
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void deleteDeadLoop(Loop *L, DominatorTree *DT, ScalarEvolution *SE,
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LoopInfo *LI);
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LoopInfo *LI, MemorySSA *MSSA = nullptr);
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/// Try to promote memory values to scalars by sinking stores out of
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/// the loop and moving loads to before the loop. We do this by looping over
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@ -18,6 +18,7 @@
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/GlobalsModRef.h"
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#include "llvm/Analysis/LoopPass.h"
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#include "llvm/Analysis/MemorySSA.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/PatternMatch.h"
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#include "llvm/InitializePasses.h"
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@ -134,7 +135,8 @@ static bool isLoopNeverExecuted(Loop *L) {
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/// is unable to delete it due to hoisting trivially loop invariant
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/// instructions out of the loop.
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static LoopDeletionResult deleteLoopIfDead(Loop *L, DominatorTree &DT,
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ScalarEvolution &SE, LoopInfo &LI) {
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ScalarEvolution &SE, LoopInfo &LI,
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MemorySSA *MSSA) {
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assert(L->isLCSSAForm(DT) && "Expected LCSSA!");
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// We can only remove the loop if there is a preheader that we can branch from
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@ -164,7 +166,7 @@ static LoopDeletionResult deleteLoopIfDead(Loop *L, DominatorTree &DT,
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std::fill(P.incoming_values().begin(), P.incoming_values().end(),
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UndefValue::get(P.getType()));
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}
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deleteDeadLoop(L, &DT, &SE, &LI);
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deleteDeadLoop(L, &DT, &SE, &LI, MSSA);
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++NumDeleted;
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return LoopDeletionResult::Deleted;
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}
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@ -200,7 +202,7 @@ static LoopDeletionResult deleteLoopIfDead(Loop *L, DominatorTree &DT,
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}
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LLVM_DEBUG(dbgs() << "Loop is invariant, delete it!");
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deleteDeadLoop(L, &DT, &SE, &LI);
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deleteDeadLoop(L, &DT, &SE, &LI, MSSA);
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++NumDeleted;
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return LoopDeletionResult::Deleted;
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@ -213,14 +215,17 @@ PreservedAnalyses LoopDeletionPass::run(Loop &L, LoopAnalysisManager &AM,
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LLVM_DEBUG(dbgs() << "Analyzing Loop for deletion: ");
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LLVM_DEBUG(L.dump());
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std::string LoopName = L.getName();
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auto Result = deleteLoopIfDead(&L, AR.DT, AR.SE, AR.LI);
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auto Result = deleteLoopIfDead(&L, AR.DT, AR.SE, AR.LI, AR.MSSA);
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if (Result == LoopDeletionResult::Unmodified)
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return PreservedAnalyses::all();
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if (Result == LoopDeletionResult::Deleted)
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Updater.markLoopAsDeleted(L, LoopName);
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return getLoopPassPreservedAnalyses();
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auto PA = getLoopPassPreservedAnalyses();
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if (AR.MSSA)
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PA.preserve<MemorySSAAnalysis>();
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return PA;
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}
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namespace {
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@ -235,6 +240,7 @@ public:
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bool runOnLoop(Loop *L, LPPassManager &) override;
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addPreserved<MemorySSAWrapperPass>();
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getLoopAnalysisUsage(AU);
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}
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};
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@ -255,11 +261,15 @@ bool LoopDeletionLegacyPass::runOnLoop(Loop *L, LPPassManager &LPM) {
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DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
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ScalarEvolution &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
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LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
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auto *MSSAAnalysis = getAnalysisIfAvailable<MemorySSAWrapperPass>();
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MemorySSA *MSSA = nullptr;
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if (MSSAAnalysis)
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MSSA = &MSSAAnalysis->getMSSA();
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LLVM_DEBUG(dbgs() << "Analyzing Loop for deletion: ");
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LLVM_DEBUG(L->dump());
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LoopDeletionResult Result = deleteLoopIfDead(L, DT, SE, LI);
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LoopDeletionResult Result = deleteLoopIfDead(L, DT, SE, LI, MSSA);
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if (Result == LoopDeletionResult::Deleted)
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LPM.markLoopAsDeleted(*L);
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@ -506,13 +506,16 @@ llvm::collectChildrenInLoop(DomTreeNode *N, const Loop *CurLoop) {
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return Worklist;
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}
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void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT = nullptr,
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ScalarEvolution *SE = nullptr,
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LoopInfo *LI = nullptr) {
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void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT, ScalarEvolution *SE,
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LoopInfo *LI, MemorySSA *MSSA) {
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assert((!DT || L->isLCSSAForm(*DT)) && "Expected LCSSA!");
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auto *Preheader = L->getLoopPreheader();
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assert(Preheader && "Preheader should exist!");
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std::unique_ptr<MemorySSAUpdater> MSSAU;
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if (MSSA)
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MSSAU = std::make_unique<MemorySSAUpdater>(MSSA);
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// Now that we know the removal is safe, remove the loop by changing the
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// branch from the preheader to go to the single exit block.
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//
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@ -585,18 +588,33 @@ void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT = nullptr,
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"Should have exactly one value and that's from the preheader!");
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}
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DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
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if (DT) {
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DTU.applyUpdates({{DominatorTree::Insert, Preheader, ExitBlock}});
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if (MSSA) {
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MSSAU->applyUpdates({{DominatorTree::Insert, Preheader, ExitBlock}}, *DT);
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if (VerifyMemorySSA)
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MSSA->verifyMemorySSA();
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}
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}
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// Disconnect the loop body by branching directly to its exit.
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Builder.SetInsertPoint(Preheader->getTerminator());
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Builder.CreateBr(ExitBlock);
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// Remove the old branch.
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Preheader->getTerminator()->eraseFromParent();
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DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
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if (DT) {
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// Update the dominator tree by informing it about the new edge from the
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// preheader to the exit and the removed edge.
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DTU.applyUpdates({{DominatorTree::Insert, Preheader, ExitBlock},
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{DominatorTree::Delete, Preheader, L->getHeader()}});
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DTU.applyUpdates({{DominatorTree::Delete, Preheader, L->getHeader()}});
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if (MSSA) {
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MSSAU->applyUpdates({{DominatorTree::Delete, Preheader, L->getHeader()}},
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*DT);
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if (VerifyMemorySSA)
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MSSA->verifyMemorySSA();
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SmallSetVector<BasicBlock *, 8> DeadBlockSet(L->block_begin(),
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L->block_end());
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MSSAU->removeBlocks(DeadBlockSet);
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}
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}
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// Use a map to unique and a vector to guarantee deterministic ordering.
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@ -657,6 +675,9 @@ void llvm::deleteDeadLoop(Loop *L, DominatorTree *DT = nullptr,
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for (auto *Block : L->blocks())
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Block->dropAllReferences();
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if (MSSA && VerifyMemorySSA)
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MSSA->verifyMemorySSA();
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if (LI) {
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// Erase the instructions and the blocks without having to worry
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// about ordering because we already dropped the references.
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