//===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
-//
+//
// The LLVM Compiler Infrastructure
//
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
//===----------------------------------------------------------------------===//
//
// This family of functions perform manipulations on basic blocks, and
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Function.h"
-#include "llvm/iTerminators.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/Target/TargetData.h"
+#include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ValueHandle.h"
#include <algorithm>
+using namespace llvm;
+
+/// DeleteDeadBlock - Delete the specified block, which must have no
+/// predecessors.
+void llvm::DeleteDeadBlock(BasicBlock *BB) {
+ assert((pred_begin(BB) == pred_end(BB) ||
+ // Can delete self loop.
+ BB->getSinglePredecessor() == BB) && "Block is not dead!");
+ TerminatorInst *BBTerm = BB->getTerminator();
+
+ // Loop through all of our successors and make sure they know that one
+ // of their predecessors is going away.
+ for (unsigned i = 0, e = BBTerm->getNumSuccessors(); i != e; ++i)
+ BBTerm->getSuccessor(i)->removePredecessor(BB);
+
+ // Zap all the instructions in the block.
+ while (!BB->empty()) {
+ Instruction &I = BB->back();
+ // If this instruction is used, replace uses with an arbitrary value.
+ // Because control flow can't get here, we don't care what we replace the
+ // value with. Note that since this block is unreachable, and all values
+ // contained within it must dominate their uses, that all uses will
+ // eventually be removed (they are themselves dead).
+ if (!I.use_empty())
+ I.replaceAllUsesWith(UndefValue::get(I.getType()));
+ BB->getInstList().pop_back();
+ }
+
+ // Zap the block!
+ BB->eraseFromParent();
+}
-namespace llvm {
+/// FoldSingleEntryPHINodes - We know that BB has one predecessor. If there are
+/// 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;
+
+ 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()));
+ PN->eraseFromParent();
+ }
+}
-// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
-// with a value, then remove and delete the original instruction.
-//
-void ReplaceInstWithValue(BasicBlock::InstListType &BIL,
- BasicBlock::iterator &BI, Value *V) {
+
+/// 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) {
+ 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;
+ }
+
+ // Can't merge if there are multiple predecessors.
+ 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;
+ for (; SI != SE; ++SI)
+ if (*SI != OnlySucc) {
+ OnlySucc = 0; // There are multiple distinct successors!
+ break;
+ }
+
+ // Can't merge if there are multiple successors.
+ if (!OnlySucc) return false;
+
+ // Can't merge if there is PHI loop.
+ for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE; ++BI) {
+ if (PHINode *PN = dyn_cast<PHINode>(BI)) {
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == PN)
+ return false;
+ } else
+ break;
+ }
+
+ // 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...
+ }
+
+ // 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);
+
+ // 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(),
+ DE = Children.end(); DI != DE; ++DI)
+ DT->changeImmediateDominator(*DI, PredDTN);
+
+ DT->eraseNode(BB);
+ }
+ }
+ }
+
+ BB->eraseFromParent();
+
+
+ return true;
+}
+
+/// ReplaceInstWithValue - Replace all uses of an instruction (specified by BI)
+/// with a value, then remove and delete the original instruction.
+///
+void llvm::ReplaceInstWithValue(BasicBlock::InstListType &BIL,
+ BasicBlock::iterator &BI, Value *V) {
Instruction &I = *BI;
// Replaces all of the uses of the instruction with uses of the value
I.replaceAllUsesWith(V);
- std::string OldName = I.getName();
-
+ // Make sure to propagate a name if there is one already.
+ if (I.hasName() && !V->hasName())
+ V->takeName(&I);
+
// Delete the unnecessary instruction now...
BI = BIL.erase(BI);
-
- // Make sure to propagate a name if there is one already...
- if (OldName.size() && !V->hasName())
- V->setName(OldName, &BIL.getParent()->getSymbolTable());
}
-// ReplaceInstWithInst - Replace the instruction specified by BI with the
-// instruction specified by I. The original instruction is deleted and BI is
-// updated to point to the new instruction.
-//
-void ReplaceInstWithInst(BasicBlock::InstListType &BIL,
- BasicBlock::iterator &BI, Instruction *I) {
+/// ReplaceInstWithInst - Replace the instruction specified by BI with the
+/// instruction specified by I. The original instruction is deleted and BI is
+/// updated to point to the new instruction.
+///
+void llvm::ReplaceInstWithInst(BasicBlock::InstListType &BIL,
+ BasicBlock::iterator &BI, Instruction *I) {
assert(I->getParent() == 0 &&
"ReplaceInstWithInst: Instruction already inserted into basic block!");
BI = New;
}
-// ReplaceInstWithInst - Replace the instruction specified by From with the
-// instruction specified by To.
-//
-void ReplaceInstWithInst(Instruction *From, Instruction *To) {
+/// ReplaceInstWithInst - Replace the instruction specified by From with the
+/// instruction specified by To.
+///
+void llvm::ReplaceInstWithInst(Instruction *From, Instruction *To) {
BasicBlock::iterator BI(From);
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 RemoveSuccessor(TerminatorInst *TI, unsigned SuccNum) {
+/// 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!");
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::VoidTy)
+ if (BB->getParent()->getReturnType() != Type::getVoidTy(TI->getContext()))
RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
// Create the return...
- NewTI = new ReturnInst(RetVal);
+ NewTI = ReturnInst::Create(TI->getContext(), RetVal);
}
- break;
+ break;
case Instruction::Invoke: // Should convert to call
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.
ReplaceInstWithInst(TI, NewTI);
}
-} // End llvm namespace
+/// 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;
+ }
+ }
+
+ // If this is a critical edge, let SplitCriticalEdge do it.
+ if (SplitCriticalEdge(BB->getTerminator(), SuccNum, P))
+ return LatchTerm->getSuccessor(SuccNum);
+
+ // If the edge isn't critical, then BB has a single successor or Succ has a
+ // single pred. Split the block.
+ BasicBlock::iterator SplitPoint;
+ if (BasicBlock *SP = Succ->getSinglePredecessor()) {
+ // If the successor only has a single pred, split the top of the successor
+ // block.
+ 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);
+ }
+}
+
+/// SplitBlock - Split the specified block at the specified instruction - every
+/// thing before SplitPt stays in Old and everything starting with SplitPt moves
+/// to a new block. The two blocks are joined by an unconditional branch and
+/// the loop info is updated.
+///
+BasicBlock *llvm::SplitBlock(BasicBlock *Old, Instruction *SplitPt, Pass *P) {
+ BasicBlock::iterator SplitIt = SplitPt;
+ while (isa<PHINode>(SplitIt))
+ ++SplitIt;
+ BasicBlock *New = Old->splitBasicBlock(SplitIt, Old->getName()+".split");
+
+ // The new block lives in whichever loop the old one did.
+ 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);
+
+ 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;
+}
+
+
+/// SplitBlockPredecessors - This method transforms BB by introducing a new
+/// basic block into the function, and moving some of the predecessors of BB to
+/// be predecessors of the new block. The new predecessors are indicated by the
+/// 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.
+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->getContext(), BB->getName()+Suffix,
+ BB->getParent(), BB);
+
+ // The new block unconditionally branches to the old block.
+ BranchInst *BI = BranchInst::Create(BB, NewBB);
+
+ // Move the edges from Preds to point to NewBB instead of BB.
+ for (unsigned i = 0; i != NumPreds; ++i)
+ Preds[i]->getTerminator()->replaceUsesOfWith(BB, NewBB);
+
+ // 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
+ // account for the newly created predecessor.
+ if (NumPreds == 0) {
+ // Insert dummy values as the incoming value.
+ for (BasicBlock::iterator I = BB->begin(); isa<PHINode>(I); ++I)
+ cast<PHINode>(I)->addIncoming(UndefValue::get(I->getType()), NewBB);
+ return 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;
+ }
+
+ 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
+ // PHI.
+ for (unsigned i = 0; i != NumPreds; ++i)
+ PN->removeIncomingValue(Preds[i], false);
+ } else {
+ // 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);
+ if (AA) AA->copyValue(PN, NewPHI);
+
+ // Move all of the PHI values for 'Preds' to the new PHI.
+ for (unsigned i = 0; i != NumPreds; ++i) {
+ Value *V = PN->removeIncomingValue(Preds[i], false);
+ NewPHI->addIncoming(V, Preds[i]);
+ }
+ InVal = NewPHI;
+ }
+
+ // Add an incoming value to the PHI node in the loop for the preheader
+ // edge.
+ PN->addIncoming(InVal, NewBB);
+
+ // 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();
+ }
+ }
+ }
+
+ 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;
+
+ 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());
+
+
+}
+
+
+
+/// 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 form identical arithmetic instructions.
+ 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))
+ return true;
+
+ // Otherwise they may not be equivalent.
+ return false;
+}
+
+/// 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);
+
+ // 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 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;
+}
+
+/// 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(I->getContext());
+ newDSPI->insertBefore(InsertPos);
+ }
+ }
+}
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