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diff --git a/contrib/llvm-project/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp b/contrib/llvm-project/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
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+//===----------------- LoopRotationUtils.cpp -----------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides utilities to convert a loop into a loop with bottom test.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/LoopRotationUtils.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/BasicAliasAnalysis.h"
+#include "llvm/Analysis/CodeMetrics.h"
+#include "llvm/Analysis/DomTreeUpdater.h"
+#include "llvm/Analysis/GlobalsModRef.h"
+#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/LoopPass.h"
+#include "llvm/Analysis/MemorySSA.h"
+#include "llvm/Analysis/MemorySSAUpdater.h"
+#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/CFG.h"
+#include "llvm/IR/DebugInfoMetadata.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/Utils/BasicBlockUtils.h"
+#include "llvm/Transforms/Utils/Cloning.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
+#include "llvm/Transforms/Utils/SSAUpdater.h"
+#include "llvm/Transforms/Utils/ValueMapper.h"
+using namespace llvm;
+
+#define DEBUG_TYPE "loop-rotate"
+
+STATISTIC(NumNotRotatedDueToHeaderSize,
+ "Number of loops not rotated due to the header size");
+STATISTIC(NumRotated, "Number of loops rotated");
+
+static cl::opt<bool>
+ MultiRotate("loop-rotate-multi", cl::init(false), cl::Hidden,
+ cl::desc("Allow loop rotation multiple times in order to reach "
+ "a better latch exit"));
+
+namespace {
+/// A simple loop rotation transformation.
+class LoopRotate {
+ const unsigned MaxHeaderSize;
+ LoopInfo *LI;
+ const TargetTransformInfo *TTI;
+ AssumptionCache *AC;
+ DominatorTree *DT;
+ ScalarEvolution *SE;
+ MemorySSAUpdater *MSSAU;
+ const SimplifyQuery &SQ;
+ bool RotationOnly;
+ bool IsUtilMode;
+ bool PrepareForLTO;
+
+public:
+ LoopRotate(unsigned MaxHeaderSize, LoopInfo *LI,
+ const TargetTransformInfo *TTI, AssumptionCache *AC,
+ DominatorTree *DT, ScalarEvolution *SE, MemorySSAUpdater *MSSAU,
+ const SimplifyQuery &SQ, bool RotationOnly, bool IsUtilMode,
+ bool PrepareForLTO)
+ : MaxHeaderSize(MaxHeaderSize), LI(LI), TTI(TTI), AC(AC), DT(DT), SE(SE),
+ MSSAU(MSSAU), SQ(SQ), RotationOnly(RotationOnly),
+ IsUtilMode(IsUtilMode), PrepareForLTO(PrepareForLTO) {}
+ bool processLoop(Loop *L);
+
+private:
+ bool rotateLoop(Loop *L, bool SimplifiedLatch);
+ bool simplifyLoopLatch(Loop *L);
+};
+} // end anonymous namespace
+
+/// Insert (K, V) pair into the ValueToValueMap, and verify the key did not
+/// previously exist in the map, and the value was inserted.
+static void InsertNewValueIntoMap(ValueToValueMapTy &VM, Value *K, Value *V) {
+ bool Inserted = VM.insert({K, V}).second;
+ assert(Inserted);
+ (void)Inserted;
+}
+/// RewriteUsesOfClonedInstructions - We just cloned the instructions from the
+/// old header into the preheader. If there were uses of the values produced by
+/// these instruction that were outside of the loop, we have to insert PHI nodes
+/// to merge the two values. Do this now.
+static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
+ BasicBlock *OrigPreheader,
+ ValueToValueMapTy &ValueMap,
+ SmallVectorImpl<PHINode*> *InsertedPHIs) {
+ // Remove PHI node entries that are no longer live.
+ BasicBlock::iterator I, E = OrigHeader->end();
+ for (I = OrigHeader->begin(); PHINode *PN = dyn_cast<PHINode>(I); ++I)
+ PN->removeIncomingValue(PN->getBasicBlockIndex(OrigPreheader));
+
+ // Now fix up users of the instructions in OrigHeader, inserting PHI nodes
+ // as necessary.
+ SSAUpdater SSA(InsertedPHIs);
+ for (I = OrigHeader->begin(); I != E; ++I) {
+ Value *OrigHeaderVal = &*I;
+
+ // If there are no uses of the value (e.g. because it returns void), there
+ // is nothing to rewrite.
+ if (OrigHeaderVal->use_empty())
+ continue;
+
+ Value *OrigPreHeaderVal = ValueMap.lookup(OrigHeaderVal);
+
+ // The value now exits in two versions: the initial value in the preheader
+ // and the loop "next" value in the original header.
+ SSA.Initialize(OrigHeaderVal->getType(), OrigHeaderVal->getName());
+ SSA.AddAvailableValue(OrigHeader, OrigHeaderVal);
+ SSA.AddAvailableValue(OrigPreheader, OrigPreHeaderVal);
+
+ // Visit each use of the OrigHeader instruction.
+ for (Value::use_iterator UI = OrigHeaderVal->use_begin(),
+ UE = OrigHeaderVal->use_end();
+ UI != UE;) {
+ // Grab the use before incrementing the iterator.
+ Use &U = *UI;
+
+ // Increment the iterator before removing the use from the list.
+ ++UI;
+
+ // SSAUpdater can't handle a non-PHI use in the same block as an
+ // earlier def. We can easily handle those cases manually.
+ Instruction *UserInst = cast<Instruction>(U.getUser());
+ if (!isa<PHINode>(UserInst)) {
+ BasicBlock *UserBB = UserInst->getParent();
+
+ // The original users in the OrigHeader are already using the
+ // original definitions.
+ if (UserBB == OrigHeader)
+ continue;
+
+ // Users in the OrigPreHeader need to use the value to which the
+ // original definitions are mapped.
+ if (UserBB == OrigPreheader) {
+ U = OrigPreHeaderVal;
+ continue;
+ }
+ }
+
+ // Anything else can be handled by SSAUpdater.
+ SSA.RewriteUse(U);
+ }
+
+ // Replace MetadataAsValue(ValueAsMetadata(OrigHeaderVal)) uses in debug
+ // intrinsics.
+ SmallVector<DbgValueInst *, 1> DbgValues;
+ llvm::findDbgValues(DbgValues, OrigHeaderVal);
+ for (auto &DbgValue : DbgValues) {
+ // The original users in the OrigHeader are already using the original
+ // definitions.
+ BasicBlock *UserBB = DbgValue->getParent();
+ if (UserBB == OrigHeader)
+ continue;
+
+ // Users in the OrigPreHeader need to use the value to which the
+ // original definitions are mapped and anything else can be handled by
+ // the SSAUpdater. To avoid adding PHINodes, check if the value is
+ // available in UserBB, if not substitute undef.
+ Value *NewVal;
+ if (UserBB == OrigPreheader)
+ NewVal = OrigPreHeaderVal;
+ else if (SSA.HasValueForBlock(UserBB))
+ NewVal = SSA.GetValueInMiddleOfBlock(UserBB);
+ else
+ NewVal = UndefValue::get(OrigHeaderVal->getType());
+ DbgValue->setOperand(0,
+ MetadataAsValue::get(OrigHeaderVal->getContext(),
+ ValueAsMetadata::get(NewVal)));
+ }
+ }
+}
+
+// Assuming both header and latch are exiting, look for a phi which is only
+// used outside the loop (via a LCSSA phi) in the exit from the header.
+// This means that rotating the loop can remove the phi.
+static bool profitableToRotateLoopExitingLatch(Loop *L) {
+ BasicBlock *Header = L->getHeader();
+ BranchInst *BI = dyn_cast<BranchInst>(Header->getTerminator());
+ assert(BI && BI->isConditional() && "need header with conditional exit");
+ BasicBlock *HeaderExit = BI->getSuccessor(0);
+ if (L->contains(HeaderExit))
+ HeaderExit = BI->getSuccessor(1);
+
+ for (auto &Phi : Header->phis()) {
+ // Look for uses of this phi in the loop/via exits other than the header.
+ if (llvm::any_of(Phi.users(), [HeaderExit](const User *U) {
+ return cast<Instruction>(U)->getParent() != HeaderExit;
+ }))
+ continue;
+ return true;
+ }
+ return false;
+}
+
+// Check that latch exit is deoptimizing (which means - very unlikely to happen)
+// and there is another exit from the loop which is non-deoptimizing.
+// If we rotate latch to that exit our loop has a better chance of being fully
+// canonical.
+//
+// It can give false positives in some rare cases.
+static bool canRotateDeoptimizingLatchExit(Loop *L) {
+ BasicBlock *Latch = L->getLoopLatch();
+ assert(Latch && "need latch");
+ BranchInst *BI = dyn_cast<BranchInst>(Latch->getTerminator());
+ // Need normal exiting latch.
+ if (!BI || !BI->isConditional())
+ return false;
+
+ BasicBlock *Exit = BI->getSuccessor(1);
+ if (L->contains(Exit))
+ Exit = BI->getSuccessor(0);
+
+ // Latch exit is non-deoptimizing, no need to rotate.
+ if (!Exit->getPostdominatingDeoptimizeCall())
+ return false;
+
+ SmallVector<BasicBlock *, 4> Exits;
+ L->getUniqueExitBlocks(Exits);
+ if (!Exits.empty()) {
+ // There is at least one non-deoptimizing exit.
+ //
+ // Note, that BasicBlock::getPostdominatingDeoptimizeCall is not exact,
+ // as it can conservatively return false for deoptimizing exits with
+ // complex enough control flow down to deoptimize call.
+ //
+ // That means here we can report success for a case where
+ // all exits are deoptimizing but one of them has complex enough
+ // control flow (e.g. with loops).
+ //
+ // That should be a very rare case and false positives for this function
+ // have compile-time effect only.
+ return any_of(Exits, [](const BasicBlock *BB) {
+ return !BB->getPostdominatingDeoptimizeCall();
+ });
+ }
+ return false;
+}
+
+/// Rotate loop LP. Return true if the loop is rotated.
+///
+/// \param SimplifiedLatch is true if the latch was just folded into the final
+/// loop exit. In this case we may want to rotate even though the new latch is
+/// now an exiting branch. This rotation would have happened had the latch not
+/// been simplified. However, if SimplifiedLatch is false, then we avoid
+/// rotating loops in which the latch exits to avoid excessive or endless
+/// rotation. LoopRotate should be repeatable and converge to a canonical
+/// form. This property is satisfied because simplifying the loop latch can only
+/// happen once across multiple invocations of the LoopRotate pass.
+///
+/// If -loop-rotate-multi is enabled we can do multiple rotations in one go
+/// so to reach a suitable (non-deoptimizing) exit.
+bool LoopRotate::rotateLoop(Loop *L, bool SimplifiedLatch) {
+ // If the loop has only one block then there is not much to rotate.
+ if (L->getBlocks().size() == 1)
+ return false;
+
+ bool Rotated = false;
+ do {
+ BasicBlock *OrigHeader = L->getHeader();
+ BasicBlock *OrigLatch = L->getLoopLatch();
+
+ BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
+ if (!BI || BI->isUnconditional())
+ return Rotated;
+
+ // If the loop header is not one of the loop exiting blocks then
+ // either this loop is already rotated or it is not
+ // suitable for loop rotation transformations.
+ if (!L->isLoopExiting(OrigHeader))
+ return Rotated;
+
+ // If the loop latch already contains a branch that leaves the loop then the
+ // loop is already rotated.
+ if (!OrigLatch)
+ return Rotated;
+
+ // Rotate if either the loop latch does *not* exit the loop, or if the loop
+ // latch was just simplified. Or if we think it will be profitable.
+ if (L->isLoopExiting(OrigLatch) && !SimplifiedLatch && IsUtilMode == false &&
+ !profitableToRotateLoopExitingLatch(L) &&
+ !canRotateDeoptimizingLatchExit(L))
+ return Rotated;
+
+ // Check size of original header and reject loop if it is very big or we can't
+ // duplicate blocks inside it.
+ {
+ SmallPtrSet<const Value *, 32> EphValues;
+ CodeMetrics::collectEphemeralValues(L, AC, EphValues);
+
+ CodeMetrics Metrics;
+ Metrics.analyzeBasicBlock(OrigHeader, *TTI, EphValues, PrepareForLTO);
+ if (Metrics.notDuplicatable) {
+ LLVM_DEBUG(
+ dbgs() << "LoopRotation: NOT rotating - contains non-duplicatable"
+ << " instructions: ";
+ L->dump());
+ return Rotated;
+ }
+ if (Metrics.convergent) {
+ LLVM_DEBUG(dbgs() << "LoopRotation: NOT rotating - contains convergent "
+ "instructions: ";
+ L->dump());
+ return Rotated;
+ }
+ if (Metrics.NumInsts > MaxHeaderSize) {
+ LLVM_DEBUG(dbgs() << "LoopRotation: NOT rotating - contains "
+ << Metrics.NumInsts
+ << " instructions, which is more than the threshold ("
+ << MaxHeaderSize << " instructions): ";
+ L->dump());
+ ++NumNotRotatedDueToHeaderSize;
+ return Rotated;
+ }
+
+ // When preparing for LTO, avoid rotating loops with calls that could be
+ // inlined during the LTO stage.
+ if (PrepareForLTO && Metrics.NumInlineCandidates > 0)
+ return Rotated;
+ }
+
+ // Now, this loop is suitable for rotation.
+ BasicBlock *OrigPreheader = L->getLoopPreheader();
+
+ // If the loop could not be converted to canonical form, it must have an
+ // indirectbr in it, just give up.
+ if (!OrigPreheader || !L->hasDedicatedExits())
+ return Rotated;
+
+ // Anything ScalarEvolution may know about this loop or the PHI nodes
+ // in its header will soon be invalidated. We should also invalidate
+ // all outer loops because insertion and deletion of blocks that happens
+ // during the rotation may violate invariants related to backedge taken
+ // infos in them.
+ if (SE)
+ SE->forgetTopmostLoop(L);
+
+ LLVM_DEBUG(dbgs() << "LoopRotation: rotating "; L->dump());
+ if (MSSAU && VerifyMemorySSA)
+ MSSAU->getMemorySSA()->verifyMemorySSA();
+
+ // Find new Loop header. NewHeader is a Header's one and only successor
+ // that is inside loop. Header's other successor is outside the
+ // loop. Otherwise loop is not suitable for rotation.
+ BasicBlock *Exit = BI->getSuccessor(0);
+ BasicBlock *NewHeader = BI->getSuccessor(1);
+ if (L->contains(Exit))
+ std::swap(Exit, NewHeader);
+ assert(NewHeader && "Unable to determine new loop header");
+ assert(L->contains(NewHeader) && !L->contains(Exit) &&
+ "Unable to determine loop header and exit blocks");
+
+ // This code assumes that the new header has exactly one predecessor.
+ // Remove any single-entry PHI nodes in it.
+ assert(NewHeader->getSinglePredecessor() &&
+ "New header doesn't have one pred!");
+ FoldSingleEntryPHINodes(NewHeader);
+
+ // Begin by walking OrigHeader and populating ValueMap with an entry for
+ // each Instruction.
+ BasicBlock::iterator I = OrigHeader->begin(), E = OrigHeader->end();
+ ValueToValueMapTy ValueMap, ValueMapMSSA;
+
+ // For PHI nodes, the value available in OldPreHeader is just the
+ // incoming value from OldPreHeader.
+ for (; PHINode *PN = dyn_cast<PHINode>(I); ++I)
+ InsertNewValueIntoMap(ValueMap, PN,
+ PN->getIncomingValueForBlock(OrigPreheader));
+
+ // For the rest of the instructions, either hoist to the OrigPreheader if
+ // possible or create a clone in the OldPreHeader if not.
+ Instruction *LoopEntryBranch = OrigPreheader->getTerminator();
+
+ // Record all debug intrinsics preceding LoopEntryBranch to avoid duplication.
+ using DbgIntrinsicHash =
+ std::pair<std::pair<Value *, DILocalVariable *>, DIExpression *>;
+ auto makeHash = [](DbgVariableIntrinsic *D) -> DbgIntrinsicHash {
+ return {{D->getVariableLocation(), D->getVariable()}, D->getExpression()};
+ };
+ SmallDenseSet<DbgIntrinsicHash, 8> DbgIntrinsics;
+ for (auto I = std::next(OrigPreheader->rbegin()), E = OrigPreheader->rend();
+ I != E; ++I) {
+ if (auto *DII = dyn_cast<DbgVariableIntrinsic>(&*I))
+ DbgIntrinsics.insert(makeHash(DII));
+ else
+ break;
+ }
+
+ // Remember the local noalias scope declarations in the header. After the
+ // rotation, they must be duplicated and the scope must be cloned. This
+ // avoids unwanted interaction across iterations.
+ SmallVector<NoAliasScopeDeclInst *, 6> NoAliasDeclInstructions;
+ for (Instruction &I : *OrigHeader)
+ if (auto *Decl = dyn_cast<NoAliasScopeDeclInst>(&I))
+ NoAliasDeclInstructions.push_back(Decl);
+
+ while (I != E) {
+ Instruction *Inst = &*I++;
+
+ // If the instruction's operands are invariant and it doesn't read or write
+ // memory, then it is safe to hoist. Doing this doesn't change the order of
+ // execution in the preheader, but does prevent the instruction from
+ // executing in each iteration of the loop. This means it is safe to hoist
+ // something that might trap, but isn't safe to hoist something that reads
+ // memory (without proving that the loop doesn't write).
+ if (L->hasLoopInvariantOperands(Inst) && !Inst->mayReadFromMemory() &&
+ !Inst->mayWriteToMemory() && !Inst->isTerminator() &&
+ !isa<DbgInfoIntrinsic>(Inst) && !isa<AllocaInst>(Inst)) {
+ Inst->moveBefore(LoopEntryBranch);
+ continue;
+ }
+
+ // Otherwise, create a duplicate of the instruction.
+ Instruction *C = Inst->clone();
+
+ // Eagerly remap the operands of the instruction.
+ RemapInstruction(C, ValueMap,
+ RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
+
+ // Avoid inserting the same intrinsic twice.
+ if (auto *DII = dyn_cast<DbgVariableIntrinsic>(C))
+ if (DbgIntrinsics.count(makeHash(DII))) {
+ C->deleteValue();
+ continue;
+ }
+
+ // With the operands remapped, see if the instruction constant folds or is
+ // otherwise simplifyable. This commonly occurs because the entry from PHI
+ // nodes allows icmps and other instructions to fold.
+ Value *V = SimplifyInstruction(C, SQ);
+ if (V && LI->replacementPreservesLCSSAForm(C, V)) {
+ // If so, then delete the temporary instruction and stick the folded value
+ // in the map.
+ InsertNewValueIntoMap(ValueMap, Inst, V);
+ if (!C->mayHaveSideEffects()) {
+ C->deleteValue();
+ C = nullptr;
+ }
+ } else {
+ InsertNewValueIntoMap(ValueMap, Inst, C);
+ }
+ if (C) {
+ // Otherwise, stick the new instruction into the new block!
+ C->setName(Inst->getName());
+ C->insertBefore(LoopEntryBranch);
+
+ if (auto *II = dyn_cast<IntrinsicInst>(C))
+ if (II->getIntrinsicID() == Intrinsic::assume)
+ AC->registerAssumption(II);
+ // MemorySSA cares whether the cloned instruction was inserted or not, and
+ // not whether it can be remapped to a simplified value.
+ if (MSSAU)
+ InsertNewValueIntoMap(ValueMapMSSA, Inst, C);
+ }
+ }
+
+ if (!NoAliasDeclInstructions.empty()) {
+ // There are noalias scope declarations:
+ // (general):
+ // Original: OrigPre { OrigHeader NewHeader ... Latch }
+ // after: (OrigPre+OrigHeader') { NewHeader ... Latch OrigHeader }
+ //
+ // with D: llvm.experimental.noalias.scope.decl,
+ // U: !noalias or !alias.scope depending on D
+ // ... { D U1 U2 } can transform into:
+ // (0) : ... { D U1 U2 } // no relevant rotation for this part
+ // (1) : ... D' { U1 U2 D } // D is part of OrigHeader
+ // (2) : ... D' U1' { U2 D U1 } // D, U1 are part of OrigHeader
+ //
+ // We now want to transform:
+ // (1) -> : ... D' { D U1 U2 D'' }
+ // (2) -> : ... D' U1' { D U2 D'' U1'' }
+ // D: original llvm.experimental.noalias.scope.decl
+ // D', U1': duplicate with replaced scopes
+ // D'', U1'': different duplicate with replaced scopes
+ // This ensures a safe fallback to 'may_alias' introduced by the rotate,
+ // as U1'' and U1' scopes will not be compatible wrt to the local restrict
+
+ // Clone the llvm.experimental.noalias.decl again for the NewHeader.
+ Instruction *NewHeaderInsertionPoint = &(*NewHeader->getFirstNonPHI());
+ for (NoAliasScopeDeclInst *NAD : NoAliasDeclInstructions) {
+ LLVM_DEBUG(dbgs() << " Cloning llvm.experimental.noalias.scope.decl:"
+ << *NAD << "\n");
+ Instruction *NewNAD = NAD->clone();
+ NewNAD->insertBefore(NewHeaderInsertionPoint);
+ }
+
+ // Scopes must now be duplicated, once for OrigHeader and once for
+ // OrigPreHeader'.
+ {
+ auto &Context = NewHeader->getContext();
+
+ SmallVector<MDNode *, 8> NoAliasDeclScopes;
+ for (NoAliasScopeDeclInst *NAD : NoAliasDeclInstructions)
+ NoAliasDeclScopes.push_back(NAD->getScopeList());
+
+ LLVM_DEBUG(dbgs() << " Updating OrigHeader scopes\n");
+ cloneAndAdaptNoAliasScopes(NoAliasDeclScopes, {OrigHeader}, Context,
+ "h.rot");
+ LLVM_DEBUG(OrigHeader->dump());
+
+ // Keep the compile time impact low by only adapting the inserted block
+ // of instructions in the OrigPreHeader. This might result in slightly
+ // more aliasing between these instructions and those that were already
+ // present, but it will be much faster when the original PreHeader is
+ // large.
+ LLVM_DEBUG(dbgs() << " Updating part of OrigPreheader scopes\n");
+ auto *FirstDecl =
+ cast<Instruction>(ValueMap[*NoAliasDeclInstructions.begin()]);
+ auto *LastInst = &OrigPreheader->back();
+ cloneAndAdaptNoAliasScopes(NoAliasDeclScopes, FirstDecl, LastInst,
+ Context, "pre.rot");
+ LLVM_DEBUG(OrigPreheader->dump());
+
+ LLVM_DEBUG(dbgs() << " Updated NewHeader:\n");
+ LLVM_DEBUG(NewHeader->dump());
+ }
+ }
+
+ // Along with all the other instructions, we just cloned OrigHeader's
+ // terminator into OrigPreHeader. Fix up the PHI nodes in each of OrigHeader's
+ // successors by duplicating their incoming values for OrigHeader.
+ for (BasicBlock *SuccBB : successors(OrigHeader))
+ for (BasicBlock::iterator BI = SuccBB->begin();
+ PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
+ PN->addIncoming(PN->getIncomingValueForBlock(OrigHeader), OrigPreheader);
+
+ // Now that OrigPreHeader has a clone of OrigHeader's terminator, remove
+ // OrigPreHeader's old terminator (the original branch into the loop), and
+ // remove the corresponding incoming values from the PHI nodes in OrigHeader.
+ LoopEntryBranch->eraseFromParent();
+
+ // Update MemorySSA before the rewrite call below changes the 1:1
+ // instruction:cloned_instruction_or_value mapping.
+ if (MSSAU) {
+ InsertNewValueIntoMap(ValueMapMSSA, OrigHeader, OrigPreheader);
+ MSSAU->updateForClonedBlockIntoPred(OrigHeader, OrigPreheader,
+ ValueMapMSSA);
+ }
+
+ SmallVector<PHINode*, 2> InsertedPHIs;
+ // If there were any uses of instructions in the duplicated block outside the
+ // loop, update them, inserting PHI nodes as required
+ RewriteUsesOfClonedInstructions(OrigHeader, OrigPreheader, ValueMap,
+ &InsertedPHIs);
+
+ // Attach dbg.value intrinsics to the new phis if that phi uses a value that
+ // previously had debug metadata attached. This keeps the debug info
+ // up-to-date in the loop body.
+ if (!InsertedPHIs.empty())
+ insertDebugValuesForPHIs(OrigHeader, InsertedPHIs);
+
+ // NewHeader is now the header of the loop.
+ L->moveToHeader(NewHeader);
+ assert(L->getHeader() == NewHeader && "Latch block is our new header");
+
+ // Inform DT about changes to the CFG.
+ if (DT) {
+ // The OrigPreheader branches to the NewHeader and Exit now. Then, inform
+ // the DT about the removed edge to the OrigHeader (that got removed).
+ SmallVector<DominatorTree::UpdateType, 3> Updates;
+ Updates.push_back({DominatorTree::Insert, OrigPreheader, Exit});
+ Updates.push_back({DominatorTree::Insert, OrigPreheader, NewHeader});
+ Updates.push_back({DominatorTree::Delete, OrigPreheader, OrigHeader});
+
+ if (MSSAU) {
+ MSSAU->applyUpdates(Updates, *DT, /*UpdateDT=*/true);
+ if (VerifyMemorySSA)
+ MSSAU->getMemorySSA()->verifyMemorySSA();
+ } else {
+ DT->applyUpdates(Updates);
+ }
+ }
+
+ // At this point, we've finished our major CFG changes. As part of cloning
+ // the loop into the preheader we've simplified instructions and the
+ // duplicated conditional branch may now be branching on a constant. If it is
+ // branching on a constant and if that constant means that we enter the loop,
+ // then we fold away the cond branch to an uncond branch. This simplifies the
+ // loop in cases important for nested loops, and it also means we don't have
+ // to split as many edges.
+ BranchInst *PHBI = cast<BranchInst>(OrigPreheader->getTerminator());
+ assert(PHBI->isConditional() && "Should be clone of BI condbr!");
+ if (!isa<ConstantInt>(PHBI->getCondition()) ||
+ PHBI->getSuccessor(cast<ConstantInt>(PHBI->getCondition())->isZero()) !=
+ NewHeader) {
+ // The conditional branch can't be folded, handle the general case.
+ // Split edges as necessary to preserve LoopSimplify form.
+
+ // Right now OrigPreHeader has two successors, NewHeader and ExitBlock, and
+ // thus is not a preheader anymore.
+ // Split the edge to form a real preheader.
+ BasicBlock *NewPH = SplitCriticalEdge(
+ OrigPreheader, NewHeader,
+ CriticalEdgeSplittingOptions(DT, LI, MSSAU).setPreserveLCSSA());
+ NewPH->setName(NewHeader->getName() + ".lr.ph");
+
+ // Preserve canonical loop form, which means that 'Exit' should have only
+ // one predecessor. Note that Exit could be an exit block for multiple
+ // nested loops, causing both of the edges to now be critical and need to
+ // be split.
+ SmallVector<BasicBlock *, 4> ExitPreds(pred_begin(Exit), pred_end(Exit));
+ bool SplitLatchEdge = false;
+ for (BasicBlock *ExitPred : ExitPreds) {
+ // We only need to split loop exit edges.
+ Loop *PredLoop = LI->getLoopFor(ExitPred);
+ if (!PredLoop || PredLoop->contains(Exit) ||
+ ExitPred->getTerminator()->isIndirectTerminator())
+ continue;
+ SplitLatchEdge |= L->getLoopLatch() == ExitPred;
+ BasicBlock *ExitSplit = SplitCriticalEdge(
+ ExitPred, Exit,
+ CriticalEdgeSplittingOptions(DT, LI, MSSAU).setPreserveLCSSA());
+ ExitSplit->moveBefore(Exit);
+ }
+ assert(SplitLatchEdge &&
+ "Despite splitting all preds, failed to split latch exit?");
+ } else {
+ // We can fold the conditional branch in the preheader, this makes things
+ // simpler. The first step is to remove the extra edge to the Exit block.
+ Exit->removePredecessor(OrigPreheader, true /*preserve LCSSA*/);
+ BranchInst *NewBI = BranchInst::Create(NewHeader, PHBI);
+ NewBI->setDebugLoc(PHBI->getDebugLoc());
+ PHBI->eraseFromParent();
+
+ // With our CFG finalized, update DomTree if it is available.
+ if (DT) DT->deleteEdge(OrigPreheader, Exit);
+
+ // Update MSSA too, if available.
+ if (MSSAU)
+ MSSAU->removeEdge(OrigPreheader, Exit);
+ }
+
+ assert(L->getLoopPreheader() && "Invalid loop preheader after loop rotation");
+ assert(L->getLoopLatch() && "Invalid loop latch after loop rotation");
+
+ if (MSSAU && VerifyMemorySSA)
+ MSSAU->getMemorySSA()->verifyMemorySSA();
+
+ // Now that the CFG and DomTree are in a consistent state again, try to merge
+ // the OrigHeader block into OrigLatch. This will succeed if they are
+ // connected by an unconditional branch. This is just a cleanup so the
+ // emitted code isn't too gross in this common case.
+ DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
+ BasicBlock *PredBB = OrigHeader->getUniquePredecessor();
+ bool DidMerge = MergeBlockIntoPredecessor(OrigHeader, &DTU, LI, MSSAU);
+ if (DidMerge)
+ RemoveRedundantDbgInstrs(PredBB);
+
+ if (MSSAU && VerifyMemorySSA)
+ MSSAU->getMemorySSA()->verifyMemorySSA();
+
+ LLVM_DEBUG(dbgs() << "LoopRotation: into "; L->dump());
+
+ ++NumRotated;
+
+ Rotated = true;
+ SimplifiedLatch = false;
+
+ // Check that new latch is a deoptimizing exit and then repeat rotation if possible.
+ // Deoptimizing latch exit is not a generally typical case, so we just loop over.
+ // TODO: if it becomes a performance bottleneck extend rotation algorithm
+ // to handle multiple rotations in one go.
+ } while (MultiRotate && canRotateDeoptimizingLatchExit(L));
+
+
+ return true;
+}
+
+/// Determine whether the instructions in this range may be safely and cheaply
+/// speculated. This is not an important enough situation to develop complex
+/// heuristics. We handle a single arithmetic instruction along with any type
+/// conversions.
+static bool shouldSpeculateInstrs(BasicBlock::iterator Begin,
+ BasicBlock::iterator End, Loop *L) {
+ bool seenIncrement = false;
+ bool MultiExitLoop = false;
+
+ if (!L->getExitingBlock())
+ MultiExitLoop = true;
+
+ for (BasicBlock::iterator I = Begin; I != End; ++I) {
+
+ if (!isSafeToSpeculativelyExecute(&*I))
+ return false;
+
+ if (isa<DbgInfoIntrinsic>(I))
+ continue;
+
+ switch (I->getOpcode()) {
+ default:
+ return false;
+ case Instruction::GetElementPtr:
+ // GEPs are cheap if all indices are constant.
+ if (!cast<GEPOperator>(I)->hasAllConstantIndices())
+ return false;
+ // fall-thru to increment case
+ LLVM_FALLTHROUGH;
+ case Instruction::Add:
+ case Instruction::Sub:
+ case Instruction::And:
+ case Instruction::Or:
+ case Instruction::Xor:
+ case Instruction::Shl:
+ case Instruction::LShr:
+ case Instruction::AShr: {
+ Value *IVOpnd =
+ !isa<Constant>(I->getOperand(0))
+ ? I->getOperand(0)
+ : !isa<Constant>(I->getOperand(1)) ? I->getOperand(1) : nullptr;
+ if (!IVOpnd)
+ return false;
+
+ // If increment operand is used outside of the loop, this speculation
+ // could cause extra live range interference.
+ if (MultiExitLoop) {
+ for (User *UseI : IVOpnd->users()) {
+ auto *UserInst = cast<Instruction>(UseI);
+ if (!L->contains(UserInst))
+ return false;
+ }
+ }
+
+ if (seenIncrement)
+ return false;
+ seenIncrement = true;
+ break;
+ }
+ case Instruction::Trunc:
+ case Instruction::ZExt:
+ case Instruction::SExt:
+ // ignore type conversions
+ break;
+ }
+ }
+ return true;
+}
+
+/// Fold the loop tail into the loop exit by speculating the loop tail
+/// instructions. Typically, this is a single post-increment. In the case of a
+/// simple 2-block loop, hoisting the increment can be much better than
+/// duplicating the entire loop header. In the case of loops with early exits,
+/// rotation will not work anyway, but simplifyLoopLatch will put the loop in
+/// canonical form so downstream passes can handle it.
+///
+/// I don't believe this invalidates SCEV.
+bool LoopRotate::simplifyLoopLatch(Loop *L) {
+ BasicBlock *Latch = L->getLoopLatch();
+ if (!Latch || Latch->hasAddressTaken())
+ return false;
+
+ BranchInst *Jmp = dyn_cast<BranchInst>(Latch->getTerminator());
+ if (!Jmp || !Jmp->isUnconditional())
+ return false;
+
+ BasicBlock *LastExit = Latch->getSinglePredecessor();
+ if (!LastExit || !L->isLoopExiting(LastExit))
+ return false;
+
+ BranchInst *BI = dyn_cast<BranchInst>(LastExit->getTerminator());
+ if (!BI)
+ return false;
+
+ if (!shouldSpeculateInstrs(Latch->begin(), Jmp->getIterator(), L))
+ return false;
+
+ LLVM_DEBUG(dbgs() << "Folding loop latch " << Latch->getName() << " into "
+ << LastExit->getName() << "\n");
+
+ DomTreeUpdater DTU(DT, DomTreeUpdater::UpdateStrategy::Eager);
+ MergeBlockIntoPredecessor(Latch, &DTU, LI, MSSAU, nullptr,
+ /*PredecessorWithTwoSuccessors=*/true);
+
+ if (MSSAU && VerifyMemorySSA)
+ MSSAU->getMemorySSA()->verifyMemorySSA();
+
+ return true;
+}
+
+/// Rotate \c L, and return true if any modification was made.
+bool LoopRotate::processLoop(Loop *L) {
+ // Save the loop metadata.
+ MDNode *LoopMD = L->getLoopID();
+
+ bool SimplifiedLatch = false;
+
+ // Simplify the loop latch before attempting to rotate the header
+ // upward. Rotation may not be needed if the loop tail can be folded into the
+ // loop exit.
+ if (!RotationOnly)
+ SimplifiedLatch = simplifyLoopLatch(L);
+
+ bool MadeChange = rotateLoop(L, SimplifiedLatch);
+ assert((!MadeChange || L->isLoopExiting(L->getLoopLatch())) &&
+ "Loop latch should be exiting after loop-rotate.");
+
+ // Restore the loop metadata.
+ // NB! We presume LoopRotation DOESN'T ADD its own metadata.
+ if ((MadeChange || SimplifiedLatch) && LoopMD)
+ L->setLoopID(LoopMD);
+
+ return MadeChange || SimplifiedLatch;
+}
+
+
+/// The utility to convert a loop into a loop with bottom test.
+bool llvm::LoopRotation(Loop *L, LoopInfo *LI, const TargetTransformInfo *TTI,
+ AssumptionCache *AC, DominatorTree *DT,
+ ScalarEvolution *SE, MemorySSAUpdater *MSSAU,
+ const SimplifyQuery &SQ, bool RotationOnly = true,
+ unsigned Threshold = unsigned(-1),
+ bool IsUtilMode = true, bool PrepareForLTO) {
+ LoopRotate LR(Threshold, LI, TTI, AC, DT, SE, MSSAU, SQ, RotationOnly,
+ IsUtilMode, PrepareForLTO);
+ return LR.processLoop(L);
+}
generated by cgit v1.2.3 (git 2.25.1) at 2025-10-10 16:00:04 +0000