mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-12-17 03:30:28 +00:00
bd75b8345f
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64278 91177308-0d34-0410-b5e6-96231b3b80d8
546 lines
20 KiB
C++
546 lines
20 KiB
C++
//===-- BasicBlockUtils.cpp - BasicBlock Utilities -------------------------==//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// 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
|
|
// instructions contained within basic blocks.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
|
|
#include "llvm/Function.h"
|
|
#include "llvm/Instructions.h"
|
|
#include "llvm/IntrinsicInst.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 <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();
|
|
Value *DbgRegionEndContext = NULL;
|
|
// 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();
|
|
// It is possible to have multiple llvm.dbg.region.end in a block.
|
|
if (DbgRegionEndInst *DREI = dyn_cast<DbgRegionEndInst>(&I))
|
|
DbgRegionEndContext = DREI->getContext();
|
|
|
|
// 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();
|
|
}
|
|
|
|
if (DbgRegionEndContext) {
|
|
// Delete corresponding llvm.dbg.func.start from entry block.
|
|
BasicBlock &Entry = BB->getParent()->getEntryBlock();
|
|
DbgFuncStartInst *DbgFuncStart = NULL;
|
|
for (BasicBlock::iterator BI = Entry.begin(), BE = Entry.end();
|
|
BI != BE; ++BI) {
|
|
if (DbgFuncStartInst *DFSI = dyn_cast<DbgFuncStartInst>(BI)) {
|
|
DbgFuncStart = DFSI;
|
|
break;
|
|
}
|
|
}
|
|
if (DbgFuncStart && DbgFuncStart->getSubprogram() == DbgRegionEndContext)
|
|
DbgFuncStart->eraseFromParent();
|
|
}
|
|
|
|
// Zap the block!
|
|
BB->eraseFromParent();
|
|
}
|
|
|
|
/// 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();
|
|
}
|
|
}
|
|
|
|
|
|
/// 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);
|
|
|
|
// 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);
|
|
}
|
|
|
|
|
|
/// 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!");
|
|
|
|
// Insert the new instruction into the basic block...
|
|
BasicBlock::iterator New = BIL.insert(BI, I);
|
|
|
|
// Replace all uses of the old instruction, and delete it.
|
|
ReplaceInstWithValue(BIL, BI, I);
|
|
|
|
// Move BI back to point to the newly inserted instruction
|
|
BI = New;
|
|
}
|
|
|
|
/// 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 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::VoidTy)
|
|
RetVal = Constant::getNullValue(BB->getParent()->getReturnType());
|
|
|
|
// Create the return...
|
|
NewTI = ReturnInst::Create(RetVal);
|
|
}
|
|
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();
|
|
}
|
|
|
|
if (NewTI) // If it's a different instruction, replace.
|
|
ReplaceInstWithInst(TI, NewTI);
|
|
}
|
|
|
|
/// 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->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;
|
|
}
|
|
|
|
/// 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->getTargetData().getTypeStoreSizeInBits(AccessTy);
|
|
}
|
|
|
|
while (ScanFrom != ScanBB->begin()) {
|
|
// Don't scan huge blocks.
|
|
if (MaxInstsToScan-- == 0) return 0;
|
|
|
|
Instruction *Inst = --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;
|
|
}
|