[llvm] 2f6987b - [LoopRotate] add ability to repeat loop rotation until non-deoptimizing exit is found
Fedor Sergeev via llvm-commits
llvm-commits at lists.llvm.org
Thu Jan 23 05:30:23 PST 2020
Author: Fedor Sergeev
Date: 2020-01-23T15:56:24+03:00
New Revision: 2f6987ba61cc31c16c64f511e5cbc76b52dc67b3
URL: https://github.com/llvm/llvm-project/commit/2f6987ba61cc31c16c64f511e5cbc76b52dc67b3
DIFF: https://github.com/llvm/llvm-project/commit/2f6987ba61cc31c16c64f511e5cbc76b52dc67b3.diff
LOG: [LoopRotate] add ability to repeat loop rotation until non-deoptimizing exit is found
In case of loops with multiple exit where all-but-one exit are deoptimizing
it might happen that the first rotation will end up with latch having a deoptimizing
exit. This makes the loop unsuitable for trip-count analysis (say, getLoopEstimatedTripCount)
as well as for loop transformations that know how to handle multple deoptimizing exits.
It pretty much means that canonical form in multple-deoptimizing-exits case should be
with non-deoptimizing exit at latch.
Teach loop-rotation to reach this canonical form by repeating rotation.
-loop-rotate-multi option introduced to control this behavior, currently disabled by default.
Reviewers: skatkov, asbirlea, reames, fhahn
Reviewed By: skatkov
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D73058
Added:
llvm/test/Transforms/LoopRotate/multiple-deopt-exits.ll
llvm/unittests/Transforms/Utils/LoopRotationUtilsTest.cpp
Modified:
llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
llvm/unittests/Transforms/Utils/CMakeLists.txt
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp b/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
index c065e0269c64..39be3d3831f0 100644
--- a/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
+++ b/llvm/lib/Transforms/Utils/LoopRotationUtils.cpp
@@ -46,6 +46,11 @@ using namespace llvm;
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 {
@@ -177,14 +182,16 @@ static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
}
}
-// 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 shouldRotateLoopExitingLatch(Loop *L) {
+// 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();
- BasicBlock *HeaderExit = Header->getTerminator()->getSuccessor(0);
+ 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 = Header->getTerminator()->getSuccessor(1);
+ HeaderExit = BI->getSuccessor(1);
for (auto &Phi : Header->phis()) {
// Look for uses of this phi in the loop/via exits other than the header.
@@ -194,7 +201,50 @@ static bool shouldRotateLoopExitingLatch(Loop *L) {
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;
}
@@ -208,319 +258,336 @@ static bool shouldRotateLoopExitingLatch(Loop *L) {
/// 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;
- BasicBlock *OrigHeader = L->getHeader();
- BasicBlock *OrigLatch = L->getLoopLatch();
-
- BranchInst *BI = dyn_cast<BranchInst>(OrigHeader->getTerminator());
- if (!BI || BI->isUnconditional())
- return false;
-
- // 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 false;
-
- // If the loop latch already contains a branch that leaves the loop then the
- // loop is already rotated.
- if (!OrigLatch)
- return false;
-
- // 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 &&
- !shouldRotateLoopExitingLatch(L))
- return false;
-
- // 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);
- if (Metrics.notDuplicatable) {
- LLVM_DEBUG(
- dbgs() << "LoopRotation: NOT rotating - contains non-duplicatable"
- << " instructions: ";
- L->dump());
- 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);
+ 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)
+ return Rotated;
}
- if (Metrics.convergent) {
- LLVM_DEBUG(dbgs() << "LoopRotation: NOT rotating - contains convergent "
- "instructions: ";
- L->dump());
- return false;
+
+ // 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;
}
- if (Metrics.NumInsts > MaxHeaderSize)
- return false;
- }
- // Now, this loop is suitable for rotation.
- BasicBlock *OrigPreheader = L->getLoopPreheader();
+ 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;
+ }
- // 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 false;
+ // Otherwise, create a duplicate of the instruction.
+ Instruction *C = Inst->clone();
- // 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);
+ // Eagerly remap the operands of the instruction.
+ RemapInstruction(C, ValueMap,
+ RF_NoModuleLevelChanges | RF_IgnoreMissingLocals);
- 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;
- }
+ // Avoid inserting the same intrinsic twice.
+ if (auto *DII = dyn_cast<DbgVariableIntrinsic>(C))
+ if (DbgIntrinsics.count(makeHash(DII))) {
+ C->deleteValue();
+ continue;
+ }
- 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;
+ // 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);
+ }
}
- // 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);
+ // 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);
+ }
- // Avoid inserting the same intrinsic twice.
- if (auto *DII = dyn_cast<DbgVariableIntrinsic>(C))
- if (DbgIntrinsics.count(makeHash(DII))) {
- C->deleteValue();
- continue;
+ 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});
+ DT->applyUpdates(Updates);
+
+ if (MSSAU) {
+ MSSAU->applyUpdates(Updates, *DT);
+ if (VerifyMemorySSA)
+ MSSAU->getMemorySSA()->verifyMemorySSA();
}
+ }
- // 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;
+ // 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 {
- 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.
+ // 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)
- InsertNewValueIntoMap(ValueMapMSSA, Inst, C);
+ MSSAU->removeEdge(OrigPreheader, Exit);
}
- }
- // 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);
- }
+ assert(L->getLoopPreheader() && "Invalid loop preheader after loop rotation");
+ assert(L->getLoopLatch() && "Invalid loop latch after loop rotation");
- 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});
- DT->applyUpdates(Updates);
+ if (MSSAU && VerifyMemorySSA)
+ MSSAU->getMemorySSA()->verifyMemorySSA();
- if (MSSAU) {
- MSSAU->applyUpdates(Updates, *DT);
- if (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);
+ MergeBlockIntoPredecessor(OrigHeader, &DTU, LI, MSSAU);
- // 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);
- }
+ if (MSSAU && VerifyMemorySSA)
+ MSSAU->getMemorySSA()->verifyMemorySSA();
- assert(L->getLoopPreheader() && "Invalid loop preheader after loop rotation");
- assert(L->getLoopLatch() && "Invalid loop latch after loop rotation");
+ LLVM_DEBUG(dbgs() << "LoopRotation: into "; L->dump());
- if (MSSAU && VerifyMemorySSA)
- MSSAU->getMemorySSA()->verifyMemorySSA();
+ ++NumRotated;
- // 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);
- MergeBlockIntoPredecessor(OrigHeader, &DTU, LI, MSSAU);
+ Rotated = true;
+ SimplifiedLatch = false;
- if (MSSAU && VerifyMemorySSA)
- MSSAU->getMemorySSA()->verifyMemorySSA();
+ // 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));
- LLVM_DEBUG(dbgs() << "LoopRotation: into "; L->dump());
- ++NumRotated;
return true;
}
diff --git a/llvm/test/Transforms/LoopRotate/multiple-deopt-exits.ll b/llvm/test/Transforms/LoopRotate/multiple-deopt-exits.ll
new file mode 100644
index 000000000000..8cf6611f75f3
--- /dev/null
+++ b/llvm/test/Transforms/LoopRotate/multiple-deopt-exits.ll
@@ -0,0 +1,165 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S < %s -loop-rotate -loop-rotate-multi=true | FileCheck %s
+; RUN: opt -S < %s -passes='loop(rotate)' -loop-rotate-multi=true | FileCheck %s
+
+; Test loop rotation with multiple exits, some of them - deoptimizing.
+; We should end up with a latch which exit is non-deoptimizing, so we should rotate
+; more than once.
+
+declare i32 @llvm.experimental.deoptimize.i32(...)
+
+define i32 @test_cond_with_one_deopt_exit(i32 * nonnull %a, i64 %x) {
+; Rotation done twice.
+; Latch should be at the 2nd condition (for.cond2), exiting to %return.
+;
+; CHECK-LABEL: @test_cond_with_one_deopt_exit(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[VAL_A_IDX3:%.*]] = load i32, i32* %a, align 4
+; CHECK-NEXT: [[ZERO_CHECK4:%.*]] = icmp eq i32 [[VAL_A_IDX3]], 0
+; CHECK-NEXT: br i1 [[ZERO_CHECK4]], label %deopt.exit, label %for.cond2.lr.ph
+; CHECK: for.cond2.lr.ph:
+; CHECK-NEXT: [[FOR_CHECK8:%.*]] = icmp ult i64 0, %x
+; CHECK-NEXT: br i1 [[FOR_CHECK8]], label %for.body.lr.ph, label %return
+; CHECK: for.body.lr.ph:
+; CHECK-NEXT: br label %for.body
+; CHECK: for.cond2:
+; CHECK: [[FOR_CHECK:%.*]] = icmp ult i64 {{%.*}}, %x
+; CHECK-NEXT: br i1 [[FOR_CHECK]], label %for.body, label %for.cond2.return_crit_edge
+; CHECK: for.body:
+; CHECK: br label %for.tail
+; CHECK: for.tail:
+; CHECK: [[VAL_A_IDX:%.*]] = load i32, i32*
+; CHECK-NEXT: [[ZERO_CHECK:%.*]] = icmp eq i32 [[VAL_A_IDX]], 0
+; CHECK-NEXT: br i1 [[ZERO_CHECK]], label %for.cond1.deopt.exit_crit_edge, label %for.cond2
+; CHECK: for.cond2.return_crit_edge:
+; CHECK-NEXT: {{%.*}} = phi i32
+; CHECK-NEXT: br label %return
+; CHECK: return:
+; CHECK-NEXT: [[SUM_LCSSA2:%.*]] = phi i32
+; CHECK-NEXT: ret i32 [[SUM_LCSSA2]]
+; CHECK: for.cond1.deopt.exit_crit_edge:
+; CHECK-NEXT: {{%.*}} = phi i32
+; CHECK-NEXT: br label %deopt.exit
+; CHECK: deopt.exit:
+; CHECK: [[DEOPT_VAL:%.*]] = call i32 (...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 {{%.*}}) ]
+; CHECK-NEXT: ret i32 [[DEOPT_VAL]]
+;
+entry:
+ br label %for.cond1
+
+for.cond1:
+ %idx = phi i64 [ 0, %entry ], [ %idx.next, %for.tail ]
+ %sum = phi i32 [ 0, %entry ], [ %sum.next, %for.tail ]
+ %a.idx = getelementptr inbounds i32, i32 *%a, i64 %idx
+ %val.a.idx = load i32, i32* %a.idx, align 4
+ %zero.check = icmp eq i32 %val.a.idx, 0
+ br i1 %zero.check, label %deopt.exit, label %for.cond2
+
+for.cond2:
+ %for.check = icmp ult i64 %idx, %x
+ br i1 %for.check, label %for.body, label %return
+
+for.body:
+ br label %for.tail
+
+for.tail:
+ %sum.next = add i32 %sum, %val.a.idx
+ %idx.next = add nuw nsw i64 %idx, 1
+ br label %for.cond1
+
+return:
+ ret i32 %sum
+
+deopt.exit:
+ %deopt.val = call i32(...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 %val.a.idx) ]
+ ret i32 %deopt.val
+}
+
+define i32 @test_cond_with_two_deopt_exits(i32 ** nonnull %a, i64 %x) {
+; Rotation done three times.
+; Latch should be at the 3rd condition (for.cond3), exiting to %return.
+;
+; CHECK-LABEL: @test_cond_with_two_deopt_exits(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: [[A_IDX_DEREF4:%.*]] = load i32*, i32** %a
+; CHECK-NEXT: [[NULL_CHECK5:%.*]] = icmp eq i32* [[A_IDX_DEREF4]], null
+; CHECK-NEXT: br i1 [[NULL_CHECK5]], label %deopt.exit1, label %for.cond2.lr.ph
+; CHECK: for.cond2.lr.ph:
+; CHECK-NEXT: [[VAL_A_IDX9:%.*]] = load i32, i32* [[A_IDX_DEREF4]], align 4
+; CHECK-NEXT: [[ZERO_CHECK10:%.*]] = icmp eq i32 [[VAL_A_IDX9]], 0
+; CHECK-NEXT: br i1 [[ZERO_CHECK10]], label %deopt.exit2, label %for.cond3.lr.ph
+; CHECK: for.cond3.lr.ph:
+; CHECK-NEXT: [[FOR_CHECK14:%.*]] = icmp ult i64 0, %x
+; CHECK-NEXT: br i1 [[FOR_CHECK14]], label %for.body.lr.ph, label %return
+; CHECK: for.body.lr.ph:
+; CHECK-NEXT: br label %for.body
+; CHECK: for.cond2:
+; CHECK: [[VAL_A_IDX:%.*]] = load i32, i32*
+; CHECK-NEXT: [[ZERO_CHECK:%.*]] = icmp eq i32 [[VAL_A_IDX]], 0
+; CHECK-NEXT: br i1 [[ZERO_CHECK]], label %for.cond2.deopt.exit2_crit_edge, label %for.cond3
+; CHECK: for.cond3:
+; CHECK: [[FOR_CHECK:%.*]] = icmp ult i64 {{%.*}}, %x
+; CHECK-NEXT: br i1 [[FOR_CHECK]], label %for.body, label %for.cond3.return_crit_edge
+; CHECK: for.body:
+; CHECK: br label %for.tail
+; CHECK: for.tail:
+; CHECK: [[IDX_NEXT:%.*]] = add nuw nsw i64 {{%.*}}, 1
+; CHECK: [[NULL_CHECK:%.*]] = icmp eq i32* {{%.*}}, null
+; CHECK-NEXT: br i1 [[NULL_CHECK]], label %for.cond1.deopt.exit1_crit_edge, label %for.cond2
+; CHECK: for.cond3.return_crit_edge:
+; CHECK-NEXT: [[SPLIT18:%.*]] = phi i32
+; CHECK-NEXT: br label %return
+; CHECK: return:
+; CHECK-NEXT: [[SUM_LCSSA2:%.*]] = phi i32
+; CHECK-NEXT: ret i32 [[SUM_LCSSA2]]
+; CHECK: for.cond1.deopt.exit1_crit_edge:
+; CHECK-NEXT: br label %deopt.exit1
+; CHECK: deopt.exit1:
+; CHECK-NEXT: [[DEOPT_VAL1:%.*]] = call i32 (...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 0) ]
+; CHECK-NEXT: ret i32 [[DEOPT_VAL1]]
+; CHECK: for.cond2.deopt.exit2_crit_edge:
+; CHECK-NEXT: [[SPLIT:%.*]] = phi i32
+; CHECK-NEXT: br label %deopt.exit2
+; CHECK: deopt.exit2:
+; CHECK-NEXT: [[VAL_A_IDX_LCSSA:%.*]] = phi i32
+; CHECK-NEXT: [[DEOPT_VAL2:%.*]] = call i32 (...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 [[VAL_A_IDX_LCSSA]]) ]
+; CHECK-NEXT: ret i32 [[DEOPT_VAL2]]
+;
+entry:
+ br label %for.cond1
+
+for.cond1:
+ %idx = phi i64 [ 0, %entry ], [ %idx.next, %for.tail ]
+ %sum = phi i32 [ 0, %entry ], [ %sum.next, %for.tail ]
+ %a.idx = getelementptr inbounds i32*, i32 **%a, i64 %idx
+ %a.idx.deref = load i32*, i32** %a.idx
+ %null.check = icmp eq i32* %a.idx.deref, null
+ br i1 %null.check, label %deopt.exit1, label %for.cond2
+
+for.cond2:
+ %val.a.idx = load i32, i32* %a.idx.deref, align 4
+ %zero.check = icmp eq i32 %val.a.idx, 0
+ br i1 %zero.check, label %deopt.exit2, label %for.cond3
+
+for.cond3:
+ %for.check = icmp ult i64 %idx, %x
+ br i1 %for.check, label %for.body, label %return
+
+for.body:
+ br label %for.tail
+
+for.tail:
+ %sum.next = add i32 %sum, %val.a.idx
+ %idx.next = add nuw nsw i64 %idx, 1
+ br label %for.cond1
+
+return:
+ ret i32 %sum
+
+deopt.exit1:
+ %deopt.val1 = call i32(...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 0) ]
+ ret i32 %deopt.val1
+deopt.exit2:
+ %deopt.val2 = call i32(...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 %val.a.idx) ]
+ ret i32 %deopt.val2
+}
diff --git a/llvm/unittests/Transforms/Utils/CMakeLists.txt b/llvm/unittests/Transforms/Utils/CMakeLists.txt
index 424f09025ea2..ef1c1d592792 100644
--- a/llvm/unittests/Transforms/Utils/CMakeLists.txt
+++ b/llvm/unittests/Transforms/Utils/CMakeLists.txt
@@ -15,6 +15,7 @@ add_llvm_unittest(UtilsTests
FunctionComparatorTest.cpp
IntegerDivisionTest.cpp
LocalTest.cpp
+ LoopRotationUtilsTest.cpp
LoopUtilsTest.cpp
SizeOptsTest.cpp
SSAUpdaterBulkTest.cpp
diff --git a/llvm/unittests/Transforms/Utils/LoopRotationUtilsTest.cpp b/llvm/unittests/Transforms/Utils/LoopRotationUtilsTest.cpp
new file mode 100644
index 000000000000..fd3d6d494749
--- /dev/null
+++ b/llvm/unittests/Transforms/Utils/LoopRotationUtilsTest.cpp
@@ -0,0 +1,166 @@
+//===- LoopRotationUtilsTest.cpp - Unit tests for LoopRotation utility ----===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/Utils/LoopRotationUtils.h"
+#include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/InstructionSimplify.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/Analysis/TargetTransformInfo.h"
+#include "llvm/AsmParser/Parser.h"
+#include "llvm/IR/Dominators.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/Support/SourceMgr.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+static std::unique_ptr<Module> parseIR(LLVMContext &C, const char *IR) {
+ SMDiagnostic Err;
+ std::unique_ptr<Module> Mod = parseAssemblyString(IR, Err, C);
+ if (!Mod)
+ Err.print("LoopRotationUtilsTest", errs());
+ return Mod;
+}
+
+/// This test contains multi-deopt-exits pattern that might allow loop rotation
+/// to trigger multiple times if multiple rotations are enabled.
+/// At least one rotation should be performed, no matter what loop rotation settings are.
+TEST(LoopRotate, MultiDeoptExit) {
+ LLVMContext C;
+
+ std::unique_ptr<Module> M = parseIR(
+ C,
+ R"(
+declare i32 @llvm.experimental.deoptimize.i32(...)
+
+define i32 @test(i32 * nonnull %a, i64 %x) {
+entry:
+ br label %for.cond1
+
+for.cond1:
+ %idx = phi i64 [ 0, %entry ], [ %idx.next, %for.tail ]
+ %sum = phi i32 [ 0, %entry ], [ %sum.next, %for.tail ]
+ %a.idx = getelementptr inbounds i32, i32 *%a, i64 %idx
+ %val.a.idx = load i32, i32* %a.idx, align 4
+ %zero.check = icmp eq i32 %val.a.idx, 0
+ br i1 %zero.check, label %deopt.exit, label %for.cond2
+
+for.cond2:
+ %for.check = icmp ult i64 %idx, %x
+ br i1 %for.check, label %for.body, label %return
+
+for.body:
+ br label %for.tail
+
+for.tail:
+ %sum.next = add i32 %sum, %val.a.idx
+ %idx.next = add nuw nsw i64 %idx, 1
+ br label %for.cond1
+
+return:
+ ret i32 %sum
+
+deopt.exit:
+ %deopt.val = call i32(...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 %val.a.idx) ]
+ ret i32 %deopt.val
+})"
+ );
+
+ auto *F = M->getFunction("test");
+ DominatorTree DT(*F);
+ LoopInfo LI(DT);
+ AssumptionCache AC(*F);
+ TargetTransformInfo TTI(M->getDataLayout());
+ TargetLibraryInfoImpl TLII;
+ TargetLibraryInfo TLI(TLII);
+ ScalarEvolution SE(*F, TLI, AC, DT, LI);
+ SimplifyQuery SQ(M->getDataLayout());
+
+ Loop *L = *LI.begin();
+
+ bool ret = LoopRotation(L, &LI, &TTI,
+ &AC, &DT,
+ &SE, nullptr,
+ SQ, true, -1, false);
+ EXPECT_TRUE(ret);
+}
+
+/// Checking a special case of multi-deopt exit loop that can not perform
+/// required amount of rotations due to the desired header containing
+/// non-duplicatable code.
+/// Similar to MultiDeoptExit test this one should do at least one rotation and
+/// pass no matter what loop rotation settings are.
+TEST(LoopRotate, MultiDeoptExit_Nondup) {
+ LLVMContext C;
+
+ std::unique_ptr<Module> M = parseIR(
+ C,
+ R"(
+; Rotation should be done once, attempted twice.
+; Second time fails due to non-duplicatable header.
+
+declare i32 @llvm.experimental.deoptimize.i32(...)
+
+declare void @nondup()
+
+define i32 @test_nondup(i32 * nonnull %a, i64 %x) {
+entry:
+ br label %for.cond1
+
+for.cond1:
+ %idx = phi i64 [ 0, %entry ], [ %idx.next, %for.tail ]
+ %sum = phi i32 [ 0, %entry ], [ %sum.next, %for.tail ]
+ %a.idx = getelementptr inbounds i32, i32 *%a, i64 %idx
+ %val.a.idx = load i32, i32* %a.idx, align 4
+ %zero.check = icmp eq i32 %val.a.idx, 0
+ br i1 %zero.check, label %deopt.exit, label %for.cond2
+
+for.cond2:
+ call void @nondup() noduplicate
+ %for.check = icmp ult i64 %idx, %x
+ br i1 %for.check, label %for.body, label %return
+
+for.body:
+ br label %for.tail
+
+for.tail:
+ %sum.next = add i32 %sum, %val.a.idx
+ %idx.next = add nuw nsw i64 %idx, 1
+ br label %for.cond1
+
+return:
+ ret i32 %sum
+
+deopt.exit:
+ %deopt.val = call i32(...) @llvm.experimental.deoptimize.i32() [ "deopt"(i32 %val.a.idx) ]
+ ret i32 %deopt.val
+})"
+ );
+
+ auto *F = M->getFunction("test_nondup");
+ DominatorTree DT(*F);
+ LoopInfo LI(DT);
+ AssumptionCache AC(*F);
+ TargetTransformInfo TTI(M->getDataLayout());
+ TargetLibraryInfoImpl TLII;
+ TargetLibraryInfo TLI(TLII);
+ ScalarEvolution SE(*F, TLI, AC, DT, LI);
+ SimplifyQuery SQ(M->getDataLayout());
+
+ Loop *L = *LI.begin();
+
+ bool ret = LoopRotation(L, &LI, &TTI,
+ &AC, &DT,
+ &SE, nullptr,
+ SQ, true, -1, false);
+ /// LoopRotation should properly report "true" as we still perform the first rotation
+ /// so we do change the IR.
+ EXPECT_TRUE(ret);
+}
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