void ComputeLiveInBlocks(AllocaInst *AI, AllocaInfo &Info,
const SmallPtrSet<BasicBlock *, 32> &DefBlocks,
SmallPtrSet<BasicBlock *, 32> &LiveInBlocks);
-
- void RewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info,
- LargeBlockInfo &LBI);
- void PromoteSingleBlockAlloca(AllocaInst *AI, AllocaInfo &Info,
- LargeBlockInfo &LBI);
-
void RenamePass(BasicBlock *BB, BasicBlock *Pred,
RenamePassData::ValVector &IncVals,
std::vector<RenamePassData> &Worklist);
}
}
+/// If there is only a single store to this value, replace any loads of it that
+/// are directly dominated by the definition with the value stored.
+static void rewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info,
+ LargeBlockInfo &LBI,
+ DominatorTree &DT,
+ AliasSetTracker *AST) {
+ StoreInst *OnlyStore = Info.OnlyStore;
+ bool StoringGlobalVal = !isa<Instruction>(OnlyStore->getOperand(0));
+ BasicBlock *StoreBB = OnlyStore->getParent();
+ int StoreIndex = -1;
+
+ // Clear out UsingBlocks. We will reconstruct it here if needed.
+ Info.UsingBlocks.clear();
+
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;) {
+ Instruction *UserInst = cast<Instruction>(*UI++);
+ if (!isa<LoadInst>(UserInst)) {
+ assert(UserInst == OnlyStore && "Should only have load/stores");
+ continue;
+ }
+ LoadInst *LI = cast<LoadInst>(UserInst);
+
+ // Okay, if we have a load from the alloca, we want to replace it with the
+ // only value stored to the alloca. We can do this if the value is
+ // dominated by the store. If not, we use the rest of the mem2reg machinery
+ // to insert the phi nodes as needed.
+ if (!StoringGlobalVal) { // Non-instructions are always dominated.
+ if (LI->getParent() == StoreBB) {
+ // If we have a use that is in the same block as the store, compare the
+ // indices of the two instructions to see which one came first. If the
+ // load came before the store, we can't handle it.
+ if (StoreIndex == -1)
+ StoreIndex = LBI.getInstructionIndex(OnlyStore);
+
+ if (unsigned(StoreIndex) > LBI.getInstructionIndex(LI)) {
+ // Can't handle this load, bail out.
+ Info.UsingBlocks.push_back(StoreBB);
+ continue;
+ }
+
+ } else if (LI->getParent() != StoreBB &&
+ !DT.dominates(StoreBB, LI->getParent())) {
+ // If the load and store are in different blocks, use BB dominance to
+ // check their relationships. If the store doesn't dom the use, bail
+ // out.
+ Info.UsingBlocks.push_back(LI->getParent());
+ continue;
+ }
+ }
+
+ // Otherwise, we *can* safely rewrite this load.
+ Value *ReplVal = OnlyStore->getOperand(0);
+ // If the replacement value is the load, this must occur in unreachable
+ // code.
+ if (ReplVal == LI)
+ ReplVal = UndefValue::get(LI->getType());
+ LI->replaceAllUsesWith(ReplVal);
+ if (AST && LI->getType()->isPointerTy())
+ AST->deleteValue(LI);
+ LI->eraseFromParent();
+ LBI.deleteValue(LI);
+ }
+}
+
+namespace {
+/// This is a helper predicate used to search by the first element of a pair.
+struct StoreIndexSearchPredicate {
+ bool operator()(const std::pair<unsigned, StoreInst *> &LHS,
+ const std::pair<unsigned, StoreInst *> &RHS) {
+ return LHS.first < RHS.first;
+ }
+};
+}
+
+/// Many allocas are only used within a single basic block. If this is the
+/// case, avoid traversing the CFG and inserting a lot of potentially useless
+/// PHI nodes by just performing a single linear pass over the basic block
+/// using the Alloca.
+///
+/// If we cannot promote this alloca (because it is read before it is written),
+/// return true. This is necessary in cases where, due to control flow, the
+/// alloca is potentially undefined on some control flow paths. e.g. code like
+/// this is potentially correct:
+///
+/// for (...) { if (c) { A = undef; undef = B; } }
+///
+/// ... so long as A is not used before undef is set.
+static void promoteSingleBlockAlloca(AllocaInst *AI, AllocaInfo &Info,
+ LargeBlockInfo &LBI,
+ AliasSetTracker *AST) {
+ // The trickiest case to handle is when we have large blocks. Because of this,
+ // this code is optimized assuming that large blocks happen. This does not
+ // significantly pessimize the small block case. This uses LargeBlockInfo to
+ // make it efficient to get the index of various operations in the block.
+
+ // Clear out UsingBlocks. We will reconstruct it here if needed.
+ Info.UsingBlocks.clear();
+
+ // Walk the use-def list of the alloca, getting the locations of all stores.
+ typedef SmallVector<std::pair<unsigned, StoreInst *>, 64> StoresByIndexTy;
+ StoresByIndexTy StoresByIndex;
+
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;
+ ++UI)
+ if (StoreInst *SI = dyn_cast<StoreInst>(*UI))
+ StoresByIndex.push_back(std::make_pair(LBI.getInstructionIndex(SI), SI));
+
+ // If there are no stores to the alloca, just replace any loads with undef.
+ if (StoresByIndex.empty()) {
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;)
+ if (LoadInst *LI = dyn_cast<LoadInst>(*UI++)) {
+ LI->replaceAllUsesWith(UndefValue::get(LI->getType()));
+ if (AST && LI->getType()->isPointerTy())
+ AST->deleteValue(LI);
+ LBI.deleteValue(LI);
+ LI->eraseFromParent();
+ }
+ return;
+ }
+
+ // Sort the stores by their index, making it efficient to do a lookup with a
+ // binary search.
+ std::sort(StoresByIndex.begin(), StoresByIndex.end());
+
+ // Walk all of the loads from this alloca, replacing them with the nearest
+ // store above them, if any.
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;) {
+ LoadInst *LI = dyn_cast<LoadInst>(*UI++);
+ if (!LI)
+ continue;
+
+ unsigned LoadIdx = LBI.getInstructionIndex(LI);
+
+ // Find the nearest store that has a lower than this load.
+ StoresByIndexTy::iterator I = std::lower_bound(
+ StoresByIndex.begin(), StoresByIndex.end(),
+ std::pair<unsigned, StoreInst *>(LoadIdx, static_cast<StoreInst *>(0)),
+ StoreIndexSearchPredicate());
+
+ // If there is no store before this load, then we can't promote this load.
+ if (I == StoresByIndex.begin()) {
+ // Can't handle this load, bail out.
+ Info.UsingBlocks.push_back(LI->getParent());
+ continue;
+ }
+
+ // Otherwise, there was a store before this load, the load takes its value.
+ --I;
+ LI->replaceAllUsesWith(I->second->getOperand(0));
+ if (AST && LI->getType()->isPointerTy())
+ AST->deleteValue(LI);
+ LI->eraseFromParent();
+ LBI.deleteValue(LI);
+ }
+}
+
void PromoteMem2Reg::run() {
Function &F = *DT.getRoot()->getParent();
// If there is only a single store to this value, replace any loads of
// it that are directly dominated by the definition with the value stored.
if (Info.DefiningBlocks.size() == 1) {
- RewriteSingleStoreAlloca(AI, Info, LBI);
+ rewriteSingleStoreAlloca(AI, Info, LBI, DT, AST);
// Finally, after the scan, check to see if the store is all that is left.
if (Info.UsingBlocks.empty()) {
// If the alloca is only read and written in one basic block, just perform a
// linear sweep over the block to eliminate it.
if (Info.OnlyUsedInOneBlock) {
- PromoteSingleBlockAlloca(AI, Info, LBI);
+ promoteSingleBlockAlloca(AI, Info, LBI, AST);
// Finally, after the scan, check to see if the stores are all that is
// left.
QueuePhiNode(DFBlocks[i].second, AllocaNum, CurrentVersion);
}
-/// If there is only a single store to this value, replace any loads of it that
-/// are directly dominated by the definition with the value stored.
-void PromoteMem2Reg::RewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info,
- LargeBlockInfo &LBI) {
- StoreInst *OnlyStore = Info.OnlyStore;
- bool StoringGlobalVal = !isa<Instruction>(OnlyStore->getOperand(0));
- BasicBlock *StoreBB = OnlyStore->getParent();
- int StoreIndex = -1;
-
- // Clear out UsingBlocks. We will reconstruct it here if needed.
- Info.UsingBlocks.clear();
-
- for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;) {
- Instruction *UserInst = cast<Instruction>(*UI++);
- if (!isa<LoadInst>(UserInst)) {
- assert(UserInst == OnlyStore && "Should only have load/stores");
- continue;
- }
- LoadInst *LI = cast<LoadInst>(UserInst);
-
- // Okay, if we have a load from the alloca, we want to replace it with the
- // only value stored to the alloca. We can do this if the value is
- // dominated by the store. If not, we use the rest of the mem2reg machinery
- // to insert the phi nodes as needed.
- if (!StoringGlobalVal) { // Non-instructions are always dominated.
- if (LI->getParent() == StoreBB) {
- // If we have a use that is in the same block as the store, compare the
- // indices of the two instructions to see which one came first. If the
- // load came before the store, we can't handle it.
- if (StoreIndex == -1)
- StoreIndex = LBI.getInstructionIndex(OnlyStore);
-
- if (unsigned(StoreIndex) > LBI.getInstructionIndex(LI)) {
- // Can't handle this load, bail out.
- Info.UsingBlocks.push_back(StoreBB);
- continue;
- }
-
- } else if (LI->getParent() != StoreBB &&
- !dominates(StoreBB, LI->getParent())) {
- // If the load and store are in different blocks, use BB dominance to
- // check their relationships. If the store doesn't dom the use, bail
- // out.
- Info.UsingBlocks.push_back(LI->getParent());
- continue;
- }
- }
-
- // Otherwise, we *can* safely rewrite this load.
- Value *ReplVal = OnlyStore->getOperand(0);
- // If the replacement value is the load, this must occur in unreachable
- // code.
- if (ReplVal == LI)
- ReplVal = UndefValue::get(LI->getType());
- LI->replaceAllUsesWith(ReplVal);
- if (AST && LI->getType()->isPointerTy())
- AST->deleteValue(LI);
- LI->eraseFromParent();
- LBI.deleteValue(LI);
- }
-}
-
-namespace {
-/// This is a helper predicate used to search by the first element of a pair.
-struct StoreIndexSearchPredicate {
- bool operator()(const std::pair<unsigned, StoreInst *> &LHS,
- const std::pair<unsigned, StoreInst *> &RHS) {
- return LHS.first < RHS.first;
- }
-};
-}
-
-/// Many allocas are only used within a single basic block. If this is the
-/// case, avoid traversing the CFG and inserting a lot of potentially useless
-/// PHI nodes by just performing a single linear pass over the basic block
-/// using the Alloca.
-///
-/// If we cannot promote this alloca (because it is read before it is written),
-/// return true. This is necessary in cases where, due to control flow, the
-/// alloca is potentially undefined on some control flow paths. e.g. code like
-/// this is potentially correct:
-///
-/// for (...) { if (c) { A = undef; undef = B; } }
-///
-/// ... so long as A is not used before undef is set.
-void PromoteMem2Reg::PromoteSingleBlockAlloca(AllocaInst *AI, AllocaInfo &Info,
- LargeBlockInfo &LBI) {
- // The trickiest case to handle is when we have large blocks. Because of this,
- // this code is optimized assuming that large blocks happen. This does not
- // significantly pessimize the small block case. This uses LargeBlockInfo to
- // make it efficient to get the index of various operations in the block.
-
- // Clear out UsingBlocks. We will reconstruct it here if needed.
- Info.UsingBlocks.clear();
-
- // Walk the use-def list of the alloca, getting the locations of all stores.
- typedef SmallVector<std::pair<unsigned, StoreInst *>, 64> StoresByIndexTy;
- StoresByIndexTy StoresByIndex;
-
- for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;
- ++UI)
- if (StoreInst *SI = dyn_cast<StoreInst>(*UI))
- StoresByIndex.push_back(std::make_pair(LBI.getInstructionIndex(SI), SI));
-
- // If there are no stores to the alloca, just replace any loads with undef.
- if (StoresByIndex.empty()) {
- for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;)
- if (LoadInst *LI = dyn_cast<LoadInst>(*UI++)) {
- LI->replaceAllUsesWith(UndefValue::get(LI->getType()));
- if (AST && LI->getType()->isPointerTy())
- AST->deleteValue(LI);
- LBI.deleteValue(LI);
- LI->eraseFromParent();
- }
- return;
- }
-
- // Sort the stores by their index, making it efficient to do a lookup with a
- // binary search.
- std::sort(StoresByIndex.begin(), StoresByIndex.end());
-
- // Walk all of the loads from this alloca, replacing them with the nearest
- // store above them, if any.
- for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E;) {
- LoadInst *LI = dyn_cast<LoadInst>(*UI++);
- if (!LI)
- continue;
-
- unsigned LoadIdx = LBI.getInstructionIndex(LI);
-
- // Find the nearest store that has a lower than this load.
- StoresByIndexTy::iterator I = std::lower_bound(
- StoresByIndex.begin(), StoresByIndex.end(),
- std::pair<unsigned, StoreInst *>(LoadIdx, static_cast<StoreInst *>(0)),
- StoreIndexSearchPredicate());
-
- // If there is no store before this load, then we can't promote this load.
- if (I == StoresByIndex.begin()) {
- // Can't handle this load, bail out.
- Info.UsingBlocks.push_back(LI->getParent());
- continue;
- }
-
- // Otherwise, there was a store before this load, the load takes its value.
- --I;
- LI->replaceAllUsesWith(I->second->getOperand(0));
- if (AST && LI->getType()->isPointerTy())
- AST->deleteValue(LI);
- LI->eraseFromParent();
- LBI.deleteValue(LI);
- }
-}
-
/// \brief Queue a phi-node to be added to a basic-block for a specific Alloca.
///
/// Returns true if there wasn't already a phi-node for that variable