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Revert "Recommit "[LV] Remove unneeded createHeaderBranch.(NFCI)""

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This reverts commit 8378a71b6c.

It looks like this patch uncovered another issue, e.g. see
https://lab.llvm.org/buildbot/#/builders/168/builds/5518
This commit is contained in:
Florian Hahn
2022-03-31 19:00:48 +01:00
parent c7639f896c
commit 14e3650f01
2 changed files with 70 additions and 34 deletions
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66
llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
View File

@@ -569,6 +569,11 @@ protected:
Value *CountRoundDown, Value *EndValue,
BasicBlock *MiddleBlock, BasicBlock *VectorHeader);
/// Introduce a conditional branch (on true, condition to be set later) at the
/// end of the header=latch connecting it to itself (across the backedge) and
/// to the exit block of \p L.
void createHeaderBranch(Loop *L);
/// Handle all cross-iteration phis in the header.
void fixCrossIterationPHIs(VPTransformState &State);
@@ -625,8 +630,9 @@ protected:
BasicBlock *emitMemRuntimeChecks(BasicBlock *Bypass);
/// Emit basic blocks (prefixed with \p Prefix) for the iteration check,
/// vector loop preheader, middle block and scalar preheader.
void createVectorLoopSkeleton(StringRef Prefix);
/// vector loop preheader, middle block and scalar preheader. Also
/// allocate a loop object for the new vector loop and return it.
Loop *createVectorLoopSkeleton(StringRef Prefix);
/// Create new phi nodes for the induction variables to resume iteration count
/// in the scalar epilogue, from where the vectorized loop left off.
@@ -2827,6 +2833,23 @@ void InnerLoopVectorizer::scalarizeInstruction(Instruction *Instr,
PredicatedInstructions.push_back(Cloned);
}
void InnerLoopVectorizer::createHeaderBranch(Loop *L) {
BasicBlock *Header = L->getHeader();
assert(!L->getLoopLatch() && "loop should not have a latch at this point");
IRBuilder<> B(Header->getTerminator());
Instruction *OldInst =
getDebugLocFromInstOrOperands(Legal->getPrimaryInduction());
setDebugLocFromInst(OldInst, &B);
// Connect the header to the exit and header blocks and replace the old
// terminator.
B.CreateCondBr(B.getTrue(), L->getUniqueExitBlock(), Header);
// Now we have two terminators. Remove the old one from the block.
Header->getTerminator()->eraseFromParent();
}
Value *InnerLoopVectorizer::getOrCreateTripCount(BasicBlock *InsertBlock) {
if (TripCount)
return TripCount;
@@ -3069,7 +3092,7 @@ BasicBlock *InnerLoopVectorizer::emitMemRuntimeChecks(BasicBlock *Bypass) {
return MemCheckBlock;
}
void InnerLoopVectorizer::createVectorLoopSkeleton(StringRef Prefix) {
Loop *InnerLoopVectorizer::createVectorLoopSkeleton(StringRef Prefix) {
LoopScalarBody = OrigLoop->getHeader();
LoopVectorPreHeader = OrigLoop->getLoopPreheader();
assert(LoopVectorPreHeader && "Invalid loop structure");
@@ -3101,8 +3124,12 @@ void InnerLoopVectorizer::createVectorLoopSkeleton(StringRef Prefix) {
BrInst->setDebugLoc(ScalarLatchTerm->getDebugLoc());
ReplaceInstWithInst(LoopMiddleBlock->getTerminator(), BrInst);
SplitBlock(LoopVectorPreHeader, LoopVectorPreHeader->getTerminator(), DT,
nullptr, nullptr, Twine(Prefix) + "vector.body");
// We intentionally don't let SplitBlock to update LoopInfo since
// LoopVectorBody should belong to another loop than LoopVectorPreHeader.
// LoopVectorBody is explicitly added to the correct place few lines later.
BasicBlock *LoopVectorBody =
SplitBlock(LoopVectorPreHeader, LoopVectorPreHeader->getTerminator(), DT,
nullptr, nullptr, Twine(Prefix) + "vector.body");
// Update dominator for loop exit.
if (!Cost->requiresScalarEpilogue(VF))
@@ -3110,6 +3137,20 @@ void InnerLoopVectorizer::createVectorLoopSkeleton(StringRef Prefix) {
// middle block to exit blocks and thus no need to update the immediate
// dominator of the exit blocks.
DT->changeImmediateDominator(LoopExitBlock, LoopMiddleBlock);
// Create and register the new vector loop.
Loop *Lp = LI->AllocateLoop();
Loop *ParentLoop = OrigLoop->getParentLoop();
// Insert the new loop into the loop nest and register the new basic blocks
// before calling any utilities such as SCEV that require valid LoopInfo.
if (ParentLoop) {
ParentLoop->addChildLoop(Lp);
} else {
LI->addTopLevelLoop(Lp);
}
Lp->addBasicBlockToLoop(LoopVectorBody, *LI);
return Lp;
}
void InnerLoopVectorizer::createInductionResumeValues(
@@ -3221,6 +3262,7 @@ BasicBlock *InnerLoopVectorizer::completeLoopSkeleton(MDNode *OrigLoopID) {
#ifdef EXPENSIVE_CHECKS
assert(DT->verify(DominatorTree::VerificationLevel::Fast));
LI->verify(*DT);
#endif
return LoopVectorPreHeader;
@@ -3274,7 +3316,7 @@ InnerLoopVectorizer::createVectorizedLoopSkeleton() {
// Create an empty vector loop, and prepare basic blocks for the runtime
// checks.
createVectorLoopSkeleton("");
Loop *Lp = createVectorLoopSkeleton("");
// Now, compare the new count to zero. If it is zero skip the vector loop and
// jump to the scalar loop. This check also covers the case where the
@@ -3292,6 +3334,8 @@ InnerLoopVectorizer::createVectorizedLoopSkeleton() {
// faster.
emitMemRuntimeChecks(LoopScalarPreHeader);
createHeaderBranch(Lp);
// Emit phis for the new starting index of the scalar loop.
createInductionResumeValues();
@@ -7578,7 +7622,7 @@ void LoopVectorizationPlanner::executePlan(ElementCount BestVF, unsigned BestUF,
// 1. Create a new empty loop. Unlink the old loop and connect the new one.
VPTransformState State{BestVF, BestUF, LI, DT, ILV.Builder, &ILV, &BestVPlan};
Value *CanonicalIVStartValue;
std::tie(State.CFG.VectorPreHeader, CanonicalIVStartValue) =
std::tie(State.CFG.PrevBB, CanonicalIVStartValue) =
ILV.createVectorizedLoopSkeleton();
ILV.collectPoisonGeneratingRecipes(State);
@@ -7695,7 +7739,7 @@ Value *InnerLoopUnroller::getBroadcastInstrs(Value *V) { return V; }
std::pair<BasicBlock *, Value *>
EpilogueVectorizerMainLoop::createEpilogueVectorizedLoopSkeleton() {
MDNode *OrigLoopID = OrigLoop->getLoopID();
createVectorLoopSkeleton("");
Loop *Lp = createVectorLoopSkeleton("");
// Generate the code to check the minimum iteration count of the vector
// epilogue (see below).
@@ -7724,6 +7768,7 @@ EpilogueVectorizerMainLoop::createEpilogueVectorizedLoopSkeleton() {
// Generate the induction variable.
Value *CountRoundDown = getOrCreateVectorTripCount(LoopVectorPreHeader);
EPI.VectorTripCount = CountRoundDown;
createHeaderBranch(Lp);
// Skip induction resume value creation here because they will be created in
// the second pass. If we created them here, they wouldn't be used anyway,
@@ -7815,7 +7860,7 @@ EpilogueVectorizerMainLoop::emitMinimumIterationCountCheck(BasicBlock *Bypass,
std::pair<BasicBlock *, Value *>
EpilogueVectorizerEpilogueLoop::createEpilogueVectorizedLoopSkeleton() {
MDNode *OrigLoopID = OrigLoop->getLoopID();
createVectorLoopSkeleton("vec.epilog.");
Loop *Lp = createVectorLoopSkeleton("vec.epilog.");
// Now, compare the remaining count and if there aren't enough iterations to
// execute the vectorized epilogue skip to the scalar part.
@@ -7896,6 +7941,9 @@ EpilogueVectorizerEpilogueLoop::createEpilogueVectorizedLoopSkeleton() {
EPResumeVal->addIncoming(ConstantInt::get(IdxTy, 0),
EPI.MainLoopIterationCountCheck);
// Generate the induction variable.
createHeaderBranch(Lp);
// Generate induction resume values. These variables save the new starting
// indexes for the scalar loop. They are used to test if there are any tail
// iterations left once the vector loop has completed.

38
llvm/lib/Transforms/Vectorize/VPlan.cpp
View File

@@ -318,14 +318,9 @@ void VPBasicBlock::execute(VPTransformState *State) {
// Temporarily terminate with unreachable until CFG is rewired.
UnreachableInst *Terminator = State->Builder.CreateUnreachable();
State->Builder.SetInsertPoint(Terminator);
State->CFG.PrevBB = NewBB;
}
if (State->CurrentVectorLoop &&
!State->CurrentVectorLoop->contains(State->CFG.PrevBB)) {
// Register NewBB in its loop. In innermost loops its the same for all BB's.
State->CurrentVectorLoop->addBasicBlockToLoop(State->CFG.PrevBB,
*State->LI);
State->CurrentVectorLoop->addBasicBlockToLoop(NewBB, *State->LI);
State->CFG.PrevBB = NewBB;
}
// 2. Fill the IR basic block with IR instructions.
@@ -452,17 +447,6 @@ void VPRegionBlock::execute(VPTransformState *State) {
ReversePostOrderTraversal<VPBlockBase *> RPOT(Entry);
if (!isReplicator()) {
// Create and register the new vector loop.
State->CurrentVectorLoop = State->LI->AllocateLoop();
Loop *ParentLoop = State->LI->getLoopFor(State->CFG.VectorPreHeader);
// Insert the new loop into the loop nest and register the new basic blocks
// before calling any utilities such as SCEV that require valid LoopInfo.
if (ParentLoop)
ParentLoop->addChildLoop(State->CurrentVectorLoop);
else
State->LI->addTopLevelLoop(State->CurrentVectorLoop);
// Visit the VPBlocks connected to "this", starting from it.
for (VPBlockBase *Block : RPOT) {
if (EnableVPlanNativePath) {
@@ -873,7 +857,7 @@ void VPlan::prepareToExecute(Value *TripCountV, Value *VectorTripCountV,
// Check if the backedge taken count is needed, and if so build it.
if (BackedgeTakenCount && BackedgeTakenCount->getNumUsers()) {
IRBuilder<> Builder(State.CFG.VectorPreHeader->getTerminator());
IRBuilder<> Builder(State.CFG.PrevBB->getTerminator());
auto *TCMO = Builder.CreateSub(TripCountV,
ConstantInt::get(TripCountV->getType(), 1),
"trip.count.minus.1");
@@ -914,16 +898,17 @@ void VPlan::prepareToExecute(Value *TripCountV, Value *VectorTripCountV,
/// LoopVectorBody basic-block was created for this. Introduce additional
/// basic-blocks as needed, and fill them all.
void VPlan::execute(VPTransformState *State) {
// Set the reverse mapping from VPValues to Values for code generation.
// 0. Set the reverse mapping from VPValues to Values for code generation.
for (auto &Entry : Value2VPValue)
State->VPValue2Value[Entry.second] = Entry.first;
// Initialize CFG state.
State->CFG.PrevVPBB = nullptr;
BasicBlock *VectorHeaderBB = State->CFG.VectorPreHeader->getSingleSuccessor();
State->CFG.PrevBB = VectorHeaderBB;
State->CFG.ExitBB = VectorHeaderBB->getSingleSuccessor();
BasicBlock *VectorPreHeaderBB = State->CFG.PrevBB;
State->CFG.VectorPreHeader = VectorPreHeaderBB;
BasicBlock *VectorHeaderBB = VectorPreHeaderBB->getSingleSuccessor();
assert(VectorHeaderBB && "Loop preheader does not have a single successor.");
State->CurrentVectorLoop = State->LI->getLoopFor(VectorHeaderBB);
State->CFG.ExitBB = State->CurrentVectorLoop->getExitBlock();
// Remove the edge between Header and Latch to allow other connections.
// Temporarily terminate with unreachable until CFG is rewired.
@@ -935,6 +920,9 @@ void VPlan::execute(VPTransformState *State) {
State->Builder.SetInsertPoint(Terminator);
// Generate code in loop body.
State->CFG.PrevVPBB = nullptr;
State->CFG.PrevBB = VectorHeaderBB;
for (VPBlockBase *Block : depth_first(Entry))
Block->execute(State);