#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Target/TargetData.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Scalar.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ValueHandle.h"
#include <algorithm>
using namespace llvm;
/// when all entries to the PHI nodes in a block are guaranteed equal, such as
/// when the block has exactly one predecessor.
void llvm::FoldSingleEntryPHINodes(BasicBlock *BB) {
- if (!isa<PHINode>(BB->begin()))
- return;
-
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
if (PN->getIncomingValue(0) != PN)
PN->replaceAllUsesWith(PN->getIncomingValue(0));
}
+/// DeleteDeadPHIs - Examine each PHI in the given block and delete it if it
+/// is dead. Also recursively delete any operands that become dead as
+/// a result. This includes tracing the def-use list from the PHI to see if
+/// it is ultimately unused or if it reaches an unused cycle.
+void llvm::DeleteDeadPHIs(BasicBlock *BB) {
+ // Recursively deleting a PHI may cause multiple PHIs to be deleted
+ // or RAUW'd undef, so use an array of WeakVH for the PHIs to delete.
+ SmallVector<WeakVH, 8> PHIs;
+ for (BasicBlock::iterator I = BB->begin();
+ PHINode *PN = dyn_cast<PHINode>(I); ++I)
+ PHIs.push_back(PN);
+
+ for (unsigned i = 0, e = PHIs.size(); i != e; ++i)
+ if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*()))
+ RecursivelyDeleteDeadPHINode(PN);
+}
+
/// MergeBlockIntoPredecessor - Attempts to merge a block into its predecessor,
/// if possible. The return value indicates success or failure.
-bool llvm::MergeBlockIntoPredecessor(BasicBlock* BB, Pass* P) {
+bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) {
pred_iterator PI(pred_begin(BB)), PE(pred_end(BB));
- // Can't merge the entry block.
- if (pred_begin(BB) == pred_end(BB)) return false;
+ // Can't merge the entry block. Don't merge away blocks who have their
+ // address taken: this is a bug if the predecessor block is the entry node
+ // (because we'd end up taking the address of the entry) and undesirable in
+ // any case.
+ if (pred_begin(BB) == pred_end(BB) ||
+ BB->hasAddressTaken()) return false;
BasicBlock *PredBB = *PI++;
for (; PI != PE; ++PI) // Search all predecessors, see if they are all same
Value *RetVal = 0;
// Create a value to return... if the function doesn't return null...
- if (BB->getParent()->getReturnType() != Type::VoidTy)
+ if (BB->getParent()->getReturnType() != Type::getVoidTy(TI->getContext()))
RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
// Create the return...
- NewTI = ReturnInst::Create(RetVal);
+ NewTI = ReturnInst::Create(TI->getContext(), RetVal);
}
break;
case Instruction::Switch: // Should remove entry
default:
case Instruction::Ret: // Cannot happen, has no successors!
- assert(0 && "Unhandled terminator instruction type in RemoveSuccessor!");
- abort();
+ llvm_unreachable("Unhandled terminator instruction type in RemoveSuccessor!");
}
if (NewTI) // If it's a different instruction, replace.
++SplitIt;
BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
- // The new block lives in whichever loop the old one did.
+ // The new block lives in whichever loop the old one did. This preserves
+ // LCSSA as well, because we force the split point to be after any PHI nodes.
if (LoopInfo* LI = P->getAnalysisIfAvailable<LoopInfo>())
if (Loop *L = LI->getLoopFor(Old))
L->addBasicBlockToLoop(New, LI->getBase());
/// Preds array, which has NumPreds elements in it. The new block is given a
/// suffix of 'Suffix'.
///
-/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree and
-/// DominanceFrontier, but no other analyses.
+/// This currently updates the LLVM IR, AliasAnalysis, DominatorTree,
+/// DominanceFrontier, LoopInfo, and LCCSA but no other analyses.
+/// In particular, it does not preserve LoopSimplify (because it's
+/// complicated to handle the case where one of the edges being split
+/// is an exit of a loop with other exits).
+///
BasicBlock *llvm::SplitBlockPredecessors(BasicBlock *BB,
BasicBlock *const *Preds,
unsigned NumPreds, const char *Suffix,
Pass *P) {
// Create new basic block, insert right before the original block.
- BasicBlock *NewBB =
- BasicBlock::Create(BB->getName()+Suffix, BB->getParent(), BB);
+ BasicBlock *NewBB = BasicBlock::Create(BB->getContext(), BB->getName()+Suffix,
+ BB->getParent(), BB);
// The new block unconditionally branches to the old block.
BranchInst *BI = BranchInst::Create(BB, NewBB);
+ LoopInfo *LI = P ? P->getAnalysisIfAvailable<LoopInfo>() : 0;
+ Loop *L = LI ? LI->getLoopFor(BB) : 0;
+ bool PreserveLCSSA = P->mustPreserveAnalysisID(LCSSAID);
+
// Move the edges from Preds to point to NewBB instead of BB.
- for (unsigned i = 0; i != NumPreds; ++i)
+ // While here, if we need to preserve loop analyses, collect
+ // some information about how this split will affect loops.
+ bool HasLoopExit = false;
+ bool IsLoopEntry = !!L;
+ bool SplitMakesNewLoopHeader = false;
+ for (unsigned i = 0; i != NumPreds; ++i) {
+ // This is slightly more strict than necessary; the minimum requirement
+ // is that there be no more than one indirectbr branching to BB. And
+ // all BlockAddress uses would need to be updated.
+ assert(!isa<IndirectBrInst>(Preds[i]->getTerminator()) &&
+ "Cannot split an edge from an IndirectBrInst");
+
Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
-
+
+ if (LI) {
+ // If we need to preserve LCSSA, determine if any of
+ // the preds is a loop exit.
+ if (PreserveLCSSA)
+ if (Loop *PL = LI->getLoopFor(Preds[i]))
+ if (!PL->contains(BB))
+ HasLoopExit = true;
+ // If we need to preserve LoopInfo, note whether any of the
+ // preds crosses an interesting loop boundary.
+ if (L) {
+ if (L->contains(Preds[i]))
+ IsLoopEntry = false;
+ else
+ SplitMakesNewLoopHeader = true;
+ }
+ }
+ }
+
// Update dominator tree and dominator frontier if available.
DominatorTree *DT = P ? P->getAnalysisIfAvailable<DominatorTree>() : 0;
if (DT)
DT->splitBlock(NewBB);
if (DominanceFrontier *DF = P ? P->getAnalysisIfAvailable<DominanceFrontier>():0)
DF->splitBlock(NewBB);
- AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
-
-
+
// Insert a new PHI node into NewBB for every PHI node in BB and that new PHI
// node becomes an incoming value for BB's phi node. However, if the Preds
// list is empty, we need to insert dummy entries into the PHI nodes in BB to
cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
return NewBB;
}
+
+ AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
+
+ if (L) {
+ if (IsLoopEntry) {
+ // Add the new block to the nearest enclosing loop (and not an
+ // adjacent loop). To find this, examine each of the predecessors and
+ // determine which loops enclose them, and select the most-nested loop
+ // which contains the loop containing the block being split.
+ Loop *InnermostPredLoop = 0;
+ for (unsigned i = 0; i != NumPreds; ++i)
+ if (Loop *PredLoop = LI->getLoopFor(Preds[i])) {
+ // Seek a loop which actually contains the block being split (to
+ // avoid adjacent loops).
+ while (PredLoop && !PredLoop->contains(BB))
+ PredLoop = PredLoop->getParentLoop();
+ // Select the most-nested of these loops which contains the block.
+ if (PredLoop &&
+ PredLoop->contains(BB) &&
+ (!InnermostPredLoop ||
+ InnermostPredLoop->getLoopDepth() < PredLoop->getLoopDepth()))
+ InnermostPredLoop = PredLoop;
+ }
+ if (InnermostPredLoop)
+ InnermostPredLoop->addBasicBlockToLoop(NewBB, LI->getBase());
+ } else {
+ L->addBasicBlockToLoop(NewBB, LI->getBase());
+ if (SplitMakesNewLoopHeader)
+ L->moveToHeader(NewBB);
+ }
+ }
// Otherwise, create a new PHI node in NewBB for each PHI node in BB.
for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ) {
PHINode *PN = cast<PHINode>(I++);
// Check to see if all of the values coming in are the same. If so, we
- // don't need to create a new PHI node.
- Value *InVal = PN->getIncomingValueForBlock(Preds[0]);
- for (unsigned i = 1; i != NumPreds; ++i)
- if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
- InVal = 0;
- break;
- }
-
+ // don't need to create a new PHI node, unless it's needed for LCSSA.
+ Value *InVal = 0;
+ if (!HasLoopExit) {
+ InVal = PN->getIncomingValueForBlock(Preds[0]);
+ for (unsigned i = 1; i != NumPreds; ++i)
+ if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
+ InVal = 0;
+ break;
+ }
+ }
+
if (InVal) {
// If all incoming values for the new PHI would be the same, just don't
// make a new PHI. Instead, just remove the incoming values from the old
// Add an incoming value to the PHI node in the loop for the preheader
// edge.
PN->addIncoming(InVal, NewBB);
+ }
+
+ return NewBB;
+}
+
+/// FindFunctionBackedges - Analyze the specified function to find all of the
+/// loop backedges in the function and return them. This is a relatively cheap
+/// (compared to computing dominators and loop info) analysis.
+///
+/// The output is added to Result, as pairs of <from,to> edge info.
+void llvm::FindFunctionBackedges(const Function &F,
+ SmallVectorImpl<std::pair<const BasicBlock*,const BasicBlock*> > &Result) {
+ const BasicBlock *BB = &F.getEntryBlock();
+ if (succ_begin(BB) == succ_end(BB))
+ return;
+
+ SmallPtrSet<const BasicBlock*, 8> Visited;
+ SmallVector<std::pair<const BasicBlock*, succ_const_iterator>, 8> VisitStack;
+ SmallPtrSet<const BasicBlock*, 8> InStack;
+
+ Visited.insert(BB);
+ VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
+ InStack.insert(BB);
+ do {
+ std::pair<const BasicBlock*, succ_const_iterator> &Top = VisitStack.back();
+ const BasicBlock *ParentBB = Top.first;
+ succ_const_iterator &I = Top.second;
- // Check to see if we can eliminate this phi node.
- if (Value *V = PN->hasConstantValue(DT != 0)) {
- Instruction *I = dyn_cast<Instruction>(V);
- if (!I || DT == 0 || DT->dominates(I, PN)) {
- PN->replaceAllUsesWith(V);
- if (AA) AA->deleteValue(PN);
- PN->eraseFromParent();
+ bool FoundNew = false;
+ while (I != succ_end(ParentBB)) {
+ BB = *I++;
+ if (Visited.insert(BB)) {
+ FoundNew = true;
+ break;
}
+ // Successor is in VisitStack, it's a back edge.
+ if (InStack.count(BB))
+ Result.push_back(std::make_pair(ParentBB, BB));
}
- }
+
+ if (FoundNew) {
+ // Go down one level if there is a unvisited successor.
+ InStack.insert(BB);
+ VisitStack.push_back(std::make_pair(BB, succ_begin(BB)));
+ } else {
+ // Go up one level.
+ InStack.erase(VisitStack.pop_back_val().first);
+ }
+ } while (!VisitStack.empty());
+
- return NewBB;
}
+
+
/// AreEquivalentAddressValues - Test if A and B will obviously have the same
/// value. This includes recognizing that %t0 and %t1 will have the same
/// value in code like this:
-/// %t0 = getelementptr @a, 0, 3
+/// %t0 = getelementptr \@a, 0, 3
/// store i32 0, i32* %t0
-/// %t1 = getelementptr @a, 0, 3
+/// %t1 = getelementptr \@a, 0, 3
/// %t2 = load i32* %t1
///
static bool AreEquivalentAddressValues(const Value *A, const Value *B) {
// Test if the values are trivially equivalent.
if (A == B) return true;
- // Test if the values come form identical arithmetic instructions.
+ // Test if the values come from identical arithmetic instructions.
+ // Use isIdenticalToWhenDefined instead of isIdenticalTo because
+ // this function is only used when one address use dominates the
+ // other, which means that they'll always either have the same
+ // value or one of them will have an undefined value.
if (isa<BinaryOperator>(A) || isa<CastInst>(A) ||
isa<PHINode>(A) || isa<GetElementPtrInst>(A))
if (const Instruction *BI = dyn_cast<Instruction>(B))
- if (cast<Instruction>(A)->isIdenticalTo(BI))
+ if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
return true;
// Otherwise they may not be equivalent.
unsigned AccessSize = 0;
if (AA) {
const Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
- AccessSize = AA->getTargetData().getTypeStoreSizeInBits(AccessTy);
+ AccessSize = AA->getTypeStoreSize(AccessTy);
}
while (ScanFrom != ScanBB->begin()) {
Instruction *Inst = --ScanFrom;
if (isa<DbgInfoIntrinsic>(Inst))
continue;
+ // We skip pointer-to-pointer bitcasts, which are NOPs.
+ // It is necessary for correctness to skip those that feed into a
+ // llvm.dbg.declare, as these are not present when debugging is off.
+ if (isa<BitCastInst>(Inst) && isa<PointerType>(Inst->getType()))
+ continue;
+
// Restore ScanFrom to expected value in case next test succeeds
ScanFrom++;
return 0;
}
-/// CopyPrecedingStopPoint - If I is immediately preceded by a StopPoint,
-/// make a copy of the stoppoint before InsertPos (presumably before copying
-/// or moving I).
-void llvm::CopyPrecedingStopPoint(Instruction *I,
- BasicBlock::iterator InsertPos) {
- if (I != I->getParent()->begin()) {
- BasicBlock::iterator BBI = I; --BBI;
- if (DbgStopPointInst *DSPI = dyn_cast<DbgStopPointInst>(BBI)) {
- DbgStopPointInst *newDSPI =
- reinterpret_cast<DbgStopPointInst*>(DSPI->clone());
- newDSPI->insertBefore(InsertPos);
- }
- }
-}