#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
-#include "llvm/LLVMContext.h"
#include "llvm/Constant.h"
#include "llvm/Type.h"
#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/Dominators.h"
+#include "llvm/Analysis/LoopInfo.h"
+#include "llvm/Analysis/MemoryDependenceAnalysis.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Transforms/Scalar.h"
/// any single-entry PHI nodes in it, fold them away. This handles the case
/// 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;
+void llvm::FoldSingleEntryPHINodes(BasicBlock *BB, Pass *P) {
+ if (!isa<PHINode>(BB->begin())) return;
+
+ AliasAnalysis *AA = 0;
+ MemoryDependenceAnalysis *MemDep = 0;
+ if (P) {
+ AA = P->getAnalysisIfAvailable<AliasAnalysis>();
+ MemDep = P->getAnalysisIfAvailable<MemoryDependenceAnalysis>();
+ }
while (PHINode *PN = dyn_cast<PHINode>(BB->begin())) {
if (PN->getIncomingValue(0) != PN)
PN->replaceAllUsesWith(PN->getIncomingValue(0));
else
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
+
+ if (MemDep)
+ MemDep->removeInstruction(PN); // Memdep updates AA itself.
+ else if (AA && isa<PointerType>(PN->getType()))
+ AA->deleteValue(PN);
+
PN->eraseFromParent();
}
}
/// 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) {
+bool 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;
PHINode *PN = dyn_cast<PHINode>(I); ++I)
PHIs.push_back(PN);
+ bool Changed = false;
for (unsigned i = 0, e = PHIs.size(); i != e; ++i)
if (PHINode *PN = dyn_cast_or_null<PHINode>(PHIs[i].operator Value*()))
- RecursivelyDeleteDeadPHINode(PN);
+ Changed |= RecursivelyDeleteDeadPHINode(PN);
+
+ return Changed;
}
/// 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) {
- 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;
-
- BasicBlock *PredBB = *PI++;
- for (; PI != PE; ++PI) // Search all predecessors, see if they are all same
- if (*PI != PredBB) {
- PredBB = 0; // There are multiple different predecessors...
- break;
- }
+bool llvm::MergeBlockIntoPredecessor(BasicBlock *BB, Pass *P) {
+ // Don't merge away blocks who have their address taken.
+ if (BB->hasAddressTaken()) return false;
- // Can't merge if there are multiple predecessors.
+ // Can't merge if there are multiple predecessors, or no predecessors.
+ BasicBlock *PredBB = BB->getUniquePredecessor();
if (!PredBB) return false;
+
// Don't break self-loops.
if (PredBB == BB) return false;
// Don't break invokes.
if (isa<InvokeInst>(PredBB->getTerminator())) return false;
succ_iterator SI(succ_begin(PredBB)), SE(succ_end(PredBB));
- BasicBlock* OnlySucc = BB;
+ BasicBlock *OnlySucc = BB;
for (; SI != SE; ++SI)
if (*SI != OnlySucc) {
OnlySucc = 0; // There are multiple distinct successors!
}
// Begin by getting rid of unneeded PHIs.
- while (PHINode *PN = dyn_cast<PHINode>(&BB->front())) {
- PN->replaceAllUsesWith(PN->getIncomingValue(0));
- BB->getInstList().pop_front(); // Delete the phi node...
- }
+ if (isa<PHINode>(BB->front()))
+ FoldSingleEntryPHINodes(BB, P);
// Delete the unconditional branch from the predecessor...
PredBB->getInstList().pop_back();
- // Move all definitions in the successor to the predecessor...
- PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
-
// Make all PHI nodes that referred to BB now refer to Pred as their
// source...
BB->replaceAllUsesWith(PredBB);
+ // Move all definitions in the successor to the predecessor...
+ PredBB->getInstList().splice(PredBB->end(), BB->getInstList());
+
// Inherit predecessors name if it exists.
if (!PredBB->hasName())
PredBB->takeName(BB);
// Finally, erase the old block and update dominator info.
if (P) {
- if (DominatorTree* DT = P->getAnalysisIfAvailable<DominatorTree>()) {
- DomTreeNode* DTN = DT->getNode(BB);
- DomTreeNode* PredDTN = DT->getNode(PredBB);
-
- if (DTN) {
- SmallPtrSet<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
- for (SmallPtrSet<DomTreeNode*, 8>::iterator DI = Children.begin(),
+ if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) {
+ if (DomTreeNode *DTN = DT->getNode(BB)) {
+ DomTreeNode *PredDTN = DT->getNode(PredBB);
+ SmallVector<DomTreeNode*, 8> Children(DTN->begin(), DTN->end());
+ for (SmallVector<DomTreeNode*, 8>::iterator DI = Children.begin(),
DE = Children.end(); DI != DE; ++DI)
DT->changeImmediateDominator(*DI, PredDTN);
DT->eraseNode(BB);
}
+
+ if (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>())
+ LI->removeBlock(BB);
+
+ if (MemoryDependenceAnalysis *MD =
+ P->getAnalysisIfAvailable<MemoryDependenceAnalysis>())
+ MD->invalidateCachedPredecessors();
}
}
BB->eraseFromParent();
-
-
return true;
}
ReplaceInstWithInst(From->getParent()->getInstList(), BI, To);
}
-/// RemoveSuccessor - Change the specified terminator instruction such that its
-/// successor SuccNum no longer exists. Because this reduces the outgoing
-/// degree of the current basic block, the actual terminator instruction itself
-/// may have to be changed. In the case where the last successor of the block
-/// is deleted, a return instruction is inserted in its place which can cause a
-/// surprising change in program behavior if it is not expected.
-///
-void llvm::RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
- assert(SuccNum < TI->getNumSuccessors() &&
- "Trying to remove a nonexistant successor!");
-
- // If our old successor block contains any PHI nodes, remove the entry in the
- // PHI nodes that comes from this branch...
- //
- BasicBlock *BB = TI->getParent();
- TI->getSuccessor(SuccNum)->removePredecessor(BB);
-
- TerminatorInst *NewTI = 0;
- switch (TI->getOpcode()) {
- case Instruction::Br:
- // If this is a conditional branch... convert to unconditional branch.
- if (TI->getNumSuccessors() == 2) {
- cast<BranchInst>(TI)->setUnconditionalDest(TI->getSuccessor(1-SuccNum));
- } else { // Otherwise convert to a return instruction...
- Value *RetVal = 0;
-
- // Create a value to return... if the function doesn't return null...
- if (BB->getParent()->getReturnType() != Type::getVoidTy(TI->getContext()))
- RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
-
- // Create the return...
- NewTI = ReturnInst::Create(TI->getContext(), RetVal);
- }
- break;
-
- case Instruction::Invoke: // Should convert to call
- case Instruction::Switch: // Should remove entry
- default:
- case Instruction::Ret: // Cannot happen, has no successors!
- llvm_unreachable("Unhandled terminator instruction type in RemoveSuccessor!");
+/// GetSuccessorNumber - Search for the specified successor of basic block BB
+/// and return its position in the terminator instruction's list of
+/// successors. It is an error to call this with a block that is not a
+/// successor.
+unsigned llvm::GetSuccessorNumber(BasicBlock *BB, BasicBlock *Succ) {
+ TerminatorInst *Term = BB->getTerminator();
+#ifndef NDEBUG
+ unsigned e = Term->getNumSuccessors();
+#endif
+ for (unsigned i = 0; ; ++i) {
+ assert(i != e && "Didn't find edge?");
+ if (Term->getSuccessor(i) == Succ)
+ return i;
}
-
- if (NewTI) // If it's a different instruction, replace.
- ReplaceInstWithInst(TI, NewTI);
+ return 0;
}
/// SplitEdge - Split the edge connecting specified block. Pass P must
/// not be NULL.
BasicBlock *llvm::SplitEdge(BasicBlock *BB, BasicBlock *Succ, Pass *P) {
- TerminatorInst *LatchTerm = BB->getTerminator();
- unsigned SuccNum = 0;
-#ifndef NDEBUG
- unsigned e = LatchTerm->getNumSuccessors();
-#endif
- for (unsigned i = 0; ; ++i) {
- assert(i != e && "Didn't find edge?");
- if (LatchTerm->getSuccessor(i) == Succ) {
- SuccNum = i;
- break;
- }
- }
+ unsigned SuccNum = GetSuccessorNumber(BB, Succ);
// If this is a critical edge, let SplitCriticalEdge do it.
- if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P))
+ TerminatorInst *LatchTerm = BB->getTerminator();
+ if (SplitCriticalEdge(LatchTerm, SuccNum, P))
return LatchTerm->getSuccessor(SuccNum);
// If the edge isn't critical, then BB has a single successor or Succ has a
assert(SP == BB && "CFG broken");
SP = NULL;
return SplitBlock(Succ, Succ->begin(), P);
- } else {
- // Otherwise, if BB has a single successor, split it at the bottom of the
- // block.
- assert(BB->getTerminator()->getNumSuccessors() == 1 &&
- "Should have a single succ!");
- return SplitBlock(BB, BB->getTerminator(), P);
}
+
+ // Otherwise, if BB has a single successor, split it at the bottom of the
+ // block.
+ assert(BB->getTerminator()->getNumSuccessors() == 1 &&
+ "Should have a single succ!");
+ return SplitBlock(BB, BB->getTerminator(), P);
}
/// SplitBlock - Split the specified block at the specified instruction - every
// 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 (LoopInfo *LI = P->getAnalysisIfAvailable<LoopInfo>())
if (Loop *L = LI->getLoopFor(Old))
L->addBasicBlockToLoop(New, LI->getBase());
- if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>())
- {
- // Old dominates New. New node domiantes all other nodes dominated by Old.
- DomTreeNode *OldNode = DT->getNode(Old);
- std::vector<DomTreeNode *> Children;
- for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
- I != E; ++I)
- Children.push_back(*I);
-
- DomTreeNode *NewNode = DT->addNewBlock(New,Old);
+ if (DominatorTree *DT = P->getAnalysisIfAvailable<DominatorTree>()) {
+ // Old dominates New. New node dominates all other nodes dominated by Old.
+ DomTreeNode *OldNode = DT->getNode(Old);
+ std::vector<DomTreeNode *> Children;
+ for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end();
+ I != E; ++I)
+ Children.push_back(*I);
+ DomTreeNode *NewNode = DT->addNewBlock(New,Old);
for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
E = Children.end(); I != E; ++I)
DT->changeImmediateDominator(*I, NewNode);
- }
+ }
- if (DominanceFrontier *DF = P->getAnalysisIfAvailable<DominanceFrontier>())
- DF->splitBlock(Old);
-
return New;
}
/// suffix of 'Suffix'.
///
/// 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).
+/// 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,
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) {
}
}
- // Update dominator tree and dominator frontier if available.
+ // Update dominator tree 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);
// 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
// If the values coming into the block are not the same, we need a PHI.
// Create the new PHI node, insert it into NewBB at the end of the block
PHINode *NewPHI =
- PHINode::Create(PN->getType(), PN->getName()+".ph", BI);
+ PHINode::Create(PN->getType(), NumPreds, PN->getName()+".ph", BI);
if (AA) AA->copyValue(PN, NewPHI);
// Move all of the PHI values for 'Preds' to the new PHI.
// Go up one level.
InStack.erase(VisitStack.pop_back_val().first);
}
- } while (!VisitStack.empty());
-
-
-}
-
-
-
-/// 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
-/// store i32 0, i32* %t0
-/// %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 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)->isIdenticalToWhenDefined(BI))
- return true;
-
- // Otherwise they may not be equivalent.
- return false;
+ } while (!VisitStack.empty());
}
-/// FindAvailableLoadedValue - Scan the ScanBB block backwards (starting at the
-/// instruction before ScanFrom) checking to see if we have the value at the
-/// memory address *Ptr locally available within a small number of instructions.
-/// If the value is available, return it.
-///
-/// If not, return the iterator for the last validated instruction that the
-/// value would be live through. If we scanned the entire block and didn't find
-/// something that invalidates *Ptr or provides it, ScanFrom would be left at
-/// begin() and this returns null. ScanFrom could also be left
-///
-/// MaxInstsToScan specifies the maximum instructions to scan in the block. If
-/// it is set to 0, it will scan the whole block. You can also optionally
-/// specify an alias analysis implementation, which makes this more precise.
-Value *llvm::FindAvailableLoadedValue(Value *Ptr, BasicBlock *ScanBB,
- BasicBlock::iterator &ScanFrom,
- unsigned MaxInstsToScan,
- AliasAnalysis *AA) {
- if (MaxInstsToScan == 0) MaxInstsToScan = ~0U;
-
- // If we're using alias analysis to disambiguate get the size of *Ptr.
- unsigned AccessSize = 0;
- if (AA) {
- const Type *AccessTy = cast<PointerType>(Ptr->getType())->getElementType();
- AccessSize = AA->getTypeStoreSize(AccessTy);
- }
-
- while (ScanFrom != ScanBB->begin()) {
- // We must ignore debug info directives when counting (otherwise they
- // would affect codegen).
- 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++;
-
- // Don't scan huge blocks.
- if (MaxInstsToScan-- == 0) return 0;
-
- --ScanFrom;
- // If this is a load of Ptr, the loaded value is available.
- if (LoadInst *LI = dyn_cast<LoadInst>(Inst))
- if (AreEquivalentAddressValues(LI->getOperand(0), Ptr))
- return LI;
-
- if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
- // If this is a store through Ptr, the value is available!
- if (AreEquivalentAddressValues(SI->getOperand(1), Ptr))
- return SI->getOperand(0);
+/// FoldReturnIntoUncondBranch - This method duplicates the specified return
+/// instruction into a predecessor which ends in an unconditional branch. If
+/// the return instruction returns a value defined by a PHI, propagate the
+/// right value into the return. It returns the new return instruction in the
+/// predecessor.
+ReturnInst *llvm::FoldReturnIntoUncondBranch(ReturnInst *RI, BasicBlock *BB,
+ BasicBlock *Pred) {
+ Instruction *UncondBranch = Pred->getTerminator();
+ // Clone the return and add it to the end of the predecessor.
+ Instruction *NewRet = RI->clone();
+ Pred->getInstList().push_back(NewRet);
- // If Ptr is an alloca and this is a store to a different alloca, ignore
- // the store. This is a trivial form of alias analysis that is important
- // for reg2mem'd code.
- if ((isa<AllocaInst>(Ptr) || isa<GlobalVariable>(Ptr)) &&
- (isa<AllocaInst>(SI->getOperand(1)) ||
- isa<GlobalVariable>(SI->getOperand(1))))
- continue;
+ // If the return instruction returns a value, and if the value was a
+ // PHI node in "BB", propagate the right value into the return.
+ for (User::op_iterator i = NewRet->op_begin(), e = NewRet->op_end();
+ i != e; ++i)
+ if (PHINode *PN = dyn_cast<PHINode>(*i))
+ if (PN->getParent() == BB)
+ *i = PN->getIncomingValueForBlock(Pred);
- // If we have alias analysis and it says the store won't modify the loaded
- // value, ignore the store.
- if (AA &&
- (AA->getModRefInfo(SI, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
- continue;
-
- // Otherwise the store that may or may not alias the pointer, bail out.
- ++ScanFrom;
- return 0;
- }
-
- // If this is some other instruction that may clobber Ptr, bail out.
- if (Inst->mayWriteToMemory()) {
- // If alias analysis claims that it really won't modify the load,
- // ignore it.
- if (AA &&
- (AA->getModRefInfo(Inst, Ptr, AccessSize) & AliasAnalysis::Mod) == 0)
- continue;
-
- // May modify the pointer, bail out.
- ++ScanFrom;
- return 0;
- }
- }
-
- // Got to the start of the block, we didn't find it, but are done for this
- // block.
- return 0;
+ // Update any PHI nodes in the returning block to realize that we no
+ // longer branch to them.
+ BB->removePredecessor(Pred);
+ UncondBranch->eraseFromParent();
+ return cast<ReturnInst>(NewRet);
}
-/// 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)) {
- CallInst *newDSPI = DSPI->clone();
- newDSPI->insertBefore(InsertPos);
- }
- }
+/// GetFirstDebugLocInBasicBlock - Return first valid DebugLoc entry in a
+/// given basic block.
+DebugLoc llvm::GetFirstDebugLocInBasicBlock(const BasicBlock *BB) {
+ if (const Instruction *I = BB->getFirstNonPHI())
+ return I->getDebugLoc();
+ // Scanning entire block may be too expensive, if the first instruction
+ // does not have valid location info.
+ return DebugLoc();
}
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