#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
+#include "llvm/IntrinsicInst.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/CFG.h"
-#include "llvm/Support/Compiler.h"
#include <algorithm>
using namespace llvm;
STATISTIC(NumDeadAlloca, "Number of dead alloca's removed");
STATISTIC(NumPHIInsert, "Number of PHI nodes inserted");
-// Provide DenseMapInfo for all pointers.
namespace llvm {
template<>
struct DenseMapInfo<std::pair<BasicBlock*, unsigned> > {
static bool isEqual(const EltTy &LHS, const EltTy &RHS) {
return LHS == RHS;
}
- static bool isPod() { return true; }
};
}
return false; // Don't allow a store OF the AI, only INTO the AI.
if (SI->isVolatile())
return false;
+ } else if (const BitCastInst *BC = dyn_cast<BitCastInst>(*UI)) {
+ // A bitcast that does not feed into debug info inhibits promotion.
+ if (!BC->hasOneUse() || !isa<DbgInfoIntrinsic>(*BC->use_begin()))
+ return false;
+ // If the only use is by debug info, this alloca will not exist in
+ // non-debug code, so don't try to promote; this ensures the same
+ // codegen with debug info. Otherwise, debug info should not
+ // inhibit promotion (but we must examine other uses).
+ if (AI->hasOneUse())
+ return false;
} else {
- return false; // Not a load or store.
+ return false;
}
return true;
struct AllocaInfo;
// Data package used by RenamePass()
- class VISIBILITY_HIDDEN RenamePassData {
+ class RenamePassData {
public:
typedef std::vector<Value *> ValVector;
- RenamePassData() {}
+ RenamePassData() : BB(NULL), Pred(NULL), Values() {}
RenamePassData(BasicBlock *B, BasicBlock *P,
const ValVector &V) : BB(B), Pred(P), Values(V) {}
BasicBlock *BB;
///
/// This functionality is important because it avoids scanning large basic
/// blocks multiple times when promoting many allocas in the same block.
- class VISIBILITY_HIDDEN LargeBlockInfo {
+ class LargeBlockInfo {
/// InstNumbers - For each instruction that we track, keep the index of the
/// instruction. The index starts out as the number of the instruction from
/// the start of the block.
}
};
- struct VISIBILITY_HIDDEN PromoteMem2Reg {
+ struct PromoteMem2Reg {
/// Allocas - The alloca instructions being promoted.
///
std::vector<AllocaInst*> Allocas;
- SmallVector<AllocaInst*, 16> &RetryList;
DominatorTree &DT;
DominanceFrontier &DF;
/// AST - An AliasSetTracker object to update. If null, don't update it.
///
AliasSetTracker *AST;
-
+
/// AllocaLookup - Reverse mapping of Allocas.
///
std::map<AllocaInst*, unsigned> AllocaLookup;
/// BBNumPreds - Lazily compute the number of predecessors a block has.
DenseMap<const BasicBlock*, unsigned> BBNumPreds;
public:
- PromoteMem2Reg(const std::vector<AllocaInst*> &A,
- SmallVector<AllocaInst*, 16> &Retry, DominatorTree &dt,
+ PromoteMem2Reg(const std::vector<AllocaInst*> &A, DominatorTree &dt,
DominanceFrontier &df, AliasSetTracker *ast)
- : Allocas(A), RetryList(Retry), DT(dt), DF(df), AST(ast) {}
+ : Allocas(A), DT(dt), DF(df), AST(ast) {}
void run();
void RewriteSingleStoreAlloca(AllocaInst *AI, AllocaInfo &Info,
LargeBlockInfo &LBI);
-
- bool PromoteLocallyUsedAlloca(BasicBlock *BB, AllocaInst *AI,
+ void PromoteSingleBlockAlloca(AllocaInst *AI, AllocaInfo &Info,
LargeBlockInfo &LBI);
- void PromoteLocallyUsedAllocas(BasicBlock *BB,
- const std::vector<AllocaInst*> &AIs,
- LargeBlockInfo &LBI);
+
void RenamePass(BasicBlock *BB, BasicBlock *Pred,
RenamePassData::ValVector &IncVals,
std::vector<RenamePassData> &Worklist);
/// ivars.
void AnalyzeAlloca(AllocaInst *AI) {
clear();
-
+
// As we scan the uses of the alloca instruction, keep track of stores,
// and decide whether all of the loads and stores to the alloca are within
// the same basic block.
- for (Value::use_iterator U = AI->use_begin(), E = AI->use_end();
- U != E; ++U) {
- Instruction *User = cast<Instruction>(*U);
+ for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
+ UI != E;) {
+ Instruction *User = cast<Instruction>(*UI++);
+ if (BitCastInst *BC = dyn_cast<BitCastInst>(User)) {
+ // Remove any uses of this alloca in DbgInfoInstrinsics.
+ assert(BC->hasOneUse() && "Unexpected alloca uses!");
+ DbgInfoIntrinsic *DI = cast<DbgInfoIntrinsic>(*BC->use_begin());
+ DI->eraseFromParent();
+ BC->eraseFromParent();
+ continue;
+ }
+
if (StoreInst *SI = dyn_cast<StoreInst>(User)) {
// Remember the basic blocks which define new values for the alloca
DefiningBlocks.push_back(SI->getParent());
void PromoteMem2Reg::run() {
Function &F = *DF.getRoot()->getParent();
- // LocallyUsedAllocas - Keep track of all of the alloca instructions which are
- // only used in a single basic block. These instructions can be efficiently
- // promoted by performing a single linear scan over that one block. Since
- // individual basic blocks are sometimes large, we group together all allocas
- // that are live in a single basic block by the basic block they are live in.
- std::map<BasicBlock*, std::vector<AllocaInst*> > LocallyUsedAllocas;
-
if (AST) PointerAllocaValues.resize(Allocas.size());
AllocaInfo Info;
// 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) {
- LocallyUsedAllocas[Info.OnlyBlock].push_back(AI);
+ PromoteSingleBlockAlloca(AI, Info, LBI);
- // Remove the alloca from the Allocas list, since it will be processed.
- RemoveFromAllocasList(AllocaNum);
- continue;
+ // Finally, after the scan, check to see if the stores are all that is
+ // left.
+ if (Info.UsingBlocks.empty()) {
+
+ // Remove the (now dead) stores and alloca.
+ while (!AI->use_empty()) {
+ StoreInst *SI = cast<StoreInst>(AI->use_back());
+ SI->eraseFromParent();
+ LBI.deleteValue(SI);
+ }
+
+ if (AST) AST->deleteValue(AI);
+ AI->eraseFromParent();
+ LBI.deleteValue(AI);
+
+ // The alloca has been processed, move on.
+ RemoveFromAllocasList(AllocaNum);
+
+ ++NumLocalPromoted;
+ continue;
+ }
}
// If we haven't computed a numbering for the BB's in the function, do so
DetermineInsertionPoint(AI, AllocaNum, Info);
}
- // Process all allocas which are only used in a single basic block.
- for (std::map<BasicBlock*, std::vector<AllocaInst*> >::iterator I =
- LocallyUsedAllocas.begin(), E = LocallyUsedAllocas.end(); I != E; ++I){
- const std::vector<AllocaInst*> &LocAllocas = I->second;
- assert(!LocAllocas.empty() && "empty alloca list??");
-
- // It's common for there to only be one alloca in the list. Handle it
- // efficiently.
- if (LocAllocas.size() == 1) {
- // If we can do the quick promotion pass, do so now.
- if (PromoteLocallyUsedAlloca(I->first, LocAllocas[0], LBI))
- RetryList.push_back(LocAllocas[0]); // Failed, retry later.
- } else {
- // Locally promote anything possible. Note that if this is unable to
- // promote a particular alloca, it puts the alloca onto the Allocas vector
- // for global processing.
- PromoteLocallyUsedAllocas(I->first, LocAllocas, LBI);
- }
- }
-
if (Allocas.empty())
return; // All of the allocas must have been trivial!
PHINode *PN = I->second;
// If this PHI node merges one value and/or undefs, get the value.
- if (Value *V = PN->hasConstantValue(true)) {
- if (!isa<Instruction>(V) ||
- properlyDominates(cast<Instruction>(V), PN)) {
- if (AST && isa<PointerType>(PN->getType()))
- AST->deleteValue(PN);
- PN->replaceAllUsesWith(V);
- PN->eraseFromParent();
- NewPhiNodes.erase(I++);
- EliminatedAPHI = true;
- continue;
- }
+ if (Value *V = PN->hasConstantValue(&DT)) {
+ if (AST && isa<PointerType>(PN->getType()))
+ AST->deleteValue(PN);
+ PN->replaceAllUsesWith(V);
+ PN->eraseFromParent();
+ NewPhiNodes.erase(I++);
+ EliminatedAPHI = true;
+ continue;
}
++I;
}
LiveInBlockWorklist.pop_back();
--i, --e;
break;
- } else if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
+ }
+
+ if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
if (LI->getOperand(0) != AI) continue;
// Okay, we found a load before a store to the alloca. It is actually
// Now that we have a set of blocks where the phi is live-in, recursively add
// their predecessors until we find the full region the value is live.
while (!LiveInBlockWorklist.empty()) {
- BasicBlock *BB = LiveInBlockWorklist.back();
- LiveInBlockWorklist.pop_back();
+ BasicBlock *BB = LiveInBlockWorklist.pop_back_val();
// The block really is live in here, insert it into the set. If already in
// the set, then it has already been processed.
}
// Otherwise, we *can* safely rewrite this load.
- LI->replaceAllUsesWith(OnlyStore->getOperand(0));
+ 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 && isa<PointerType>(LI->getType()))
AST->deleteValue(LI);
LI->eraseFromParent();
}
}
+namespace {
-/// PromoteLocallyUsedAlloca - Many allocas are only used within a single basic
+/// StoreIndexSearchPredicate - 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;
+ }
+};
+
+}
+
+/// PromoteSingleBlockAlloca - 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.
///
/// ... so long as A is not used before undef is set.
///
-bool PromoteMem2Reg::PromoteLocallyUsedAlloca(BasicBlock *BB, AllocaInst *AI,
+void PromoteMem2Reg::PromoteSingleBlockAlloca(AllocaInst *AI, AllocaInfo &Info,
LargeBlockInfo &LBI) {
- assert(!AI->use_empty() && "There are no uses of the alloca!");
-
- // Handle degenerate cases quickly.
- if (AI->hasOneUse()) {
- Instruction *U = cast<Instruction>(AI->use_back());
- if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
- // Must be a load of uninitialized value.
- LI->replaceAllUsesWith(UndefValue::get(AI->getAllocatedType()));
- if (AST && isa<PointerType>(LI->getType()))
- AST->deleteValue(LI);
- } else {
- // Otherwise it must be a store which is never read.
- assert(isa<StoreInst>(U));
- }
- LBI.deleteValue(U);
- BB->getInstList().erase(U);
- } else {
- // Uses of the uninitialized memory location shall get undef.
- Value *CurVal = 0;
-
- for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
- Instruction *Inst = I++;
- if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
- if (LI->getOperand(0) == AI) {
- if (!CurVal) return true; // Could not locally promote!
-
- // Loads just returns the "current value"...
- LI->replaceAllUsesWith(CurVal);
- if (AST && isa<PointerType>(LI->getType()))
- AST->deleteValue(LI);
- BB->getInstList().erase(LI);
- LBI.deleteValue(LI);
- }
- } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
- if (SI->getOperand(1) == AI) {
- // Store updates the "current value"...
- CurVal = SI->getOperand(0);
- BB->getInstList().erase(SI);
- LBI.deleteValue(SI);
- }
+ // 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 && isa<PointerType>(LI->getType()))
+ AST->deleteValue(LI);
+ LBI.deleteValue(LI);
+ LI->eraseFromParent();
}
- }
- }
-
- // After traversing the basic block, there should be no more uses of the
- // alloca: remove it now.
- assert(AI->use_empty() && "Uses of alloca from more than one BB??");
- if (AST) AST->deleteValue(AI);
- AI->eraseFromParent();
- LBI.deleteValue(AI);
-
- ++NumLocalPromoted;
- return false;
-}
-
-/// PromoteLocallyUsedAllocas - This method is just like
-/// PromoteLocallyUsedAlloca, except that it processes multiple alloca
-/// instructions in parallel. This is important in cases where we have large
-/// basic blocks, as we don't want to rescan the entire basic block for each
-/// alloca which is locally used in it (which might be a lot).
-void PromoteMem2Reg::
-PromoteLocallyUsedAllocas(BasicBlock *BB, const std::vector<AllocaInst*> &AIs,
- LargeBlockInfo &LBI) {
- DenseMap<AllocaInst*, Value*> CurValues;
- for (unsigned i = 0, e = AIs.size(); i != e; ++i)
- CurValues[AIs[i]] = 0; // Insert with null value
-
- for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
- Instruction *Inst = I++;
- if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
- // Is this a load of an alloca we are tracking?
- if (AllocaInst *AI = dyn_cast<AllocaInst>(LI->getOperand(0))) {
- DenseMap<AllocaInst*, Value*>::iterator AIt = CurValues.find(AI);
- if (AIt != CurValues.end()) {
- // If loading an uninitialized value, allow the inter-block case to
- // handle it. Due to control flow, this might actually be ok.
- if (AIt->second == 0) { // Use of locally uninitialized value??
- RetryList.push_back(AI); // Retry elsewhere.
- CurValues.erase(AIt); // Stop tracking this here.
- if (CurValues.empty()) return;
- } else {
- // Loads just returns the "current value"...
- LI->replaceAllUsesWith(AIt->second);
- if (AST && isa<PointerType>(LI->getType()))
- AST->deleteValue(LI);
- BB->getInstList().erase(LI);
- LBI.deleteValue(LI);
- }
- }
- }
- } else if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
- if (AllocaInst *AI = dyn_cast<AllocaInst>(SI->getOperand(1))) {
- DenseMap<AllocaInst*, Value*>::iterator AIt = CurValues.find(AI);
- if (AIt != CurValues.end()) {
- // Store updates the "current value"...
- AIt->second = SI->getOperand(0);
- SI->eraseFromParent();
- LBI.deleteValue(SI);
- }
- }
- }
+ return;
}
- // At the end of the block scan, all allocas in CurValues are dead.
- for (DenseMap<AllocaInst*, Value*>::iterator I = CurValues.begin(),
- E = CurValues.end(); I != E; ++I) {
- AllocaInst *AI = I->first;
- assert(AI->use_empty() && "Uses of alloca from more than one BB??");
- if (AST) AST->deleteValue(AI);
- AI->eraseFromParent();
- LBI.deleteValue(AI);
+ // 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, 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 && isa<PointerType>(LI->getType()))
+ AST->deleteValue(LI);
+ LI->eraseFromParent();
+ LBI.deleteValue(LI);
}
-
- NumLocalPromoted += CurValues.size();
}
-
// QueuePhiNode - queues 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
//
// Create a PhiNode using the dereferenced type... and add the phi-node to the
// BasicBlock.
PN = PHINode::Create(Allocas[AllocaNo]->getAllocatedType(),
- Allocas[AllocaNo]->getName() + "." +
- utostr(Version++), BB->begin());
+ Allocas[AllocaNo]->getName() + "." + Twine(Version++),
+ BB->begin());
++NumPHIInsert;
PhiToAllocaMap[PN] = AllocaNo;
PN->reserveOperandSpace(getNumPreds(BB));
// If we are inserting any phi nodes into this BB, they will already be in the
// block.
if (PHINode *APN = dyn_cast<PHINode>(BB->begin())) {
- // Pred may have multiple edges to BB. If so, we want to add N incoming
- // values to each PHI we are inserting on the first time we see the edge.
- // Check to see if APN already has incoming values from Pred. This also
- // prevents us from modifying PHI nodes that are not currently being
- // inserted.
- bool HasPredEntries = false;
- for (unsigned i = 0, e = APN->getNumIncomingValues(); i != e; ++i) {
- if (APN->getIncomingBlock(i) == Pred) {
- HasPredEntries = true;
- break;
- }
- }
-
// If we have PHI nodes to update, compute the number of edges from Pred to
// BB.
- if (!HasPredEntries) {
+ if (PhiToAllocaMap.count(APN)) {
// We want to be able to distinguish between PHI nodes being inserted by
// this invocation of mem2reg from those phi nodes that already existed in
// the IR before mem2reg was run. We determine that APN is being inserted
succ_iterator I = succ_begin(BB), E = succ_end(BB);
if (I == E) return;
- // Handle the last successor without using the worklist. This allows us to
- // handle unconditional branches directly, for example.
- --E;
- for (; I != E; ++I)
- Worklist.push_back(RenamePassData(*I, BB, IncomingVals));
+ // Keep track of the successors so we don't visit the same successor twice
+ SmallPtrSet<BasicBlock*, 8> VisitedSuccs;
+ // Handle the first successor without using the worklist.
+ VisitedSuccs.insert(*I);
Pred = BB;
BB = *I;
+ ++I;
+
+ for (; I != E; ++I)
+ if (VisitedSuccs.insert(*I))
+ Worklist.push_back(RenamePassData(*I, Pred, IncomingVals));
+
goto NextIteration;
}
// If there is nothing to do, bail out...
if (Allocas.empty()) return;
- SmallVector<AllocaInst*, 16> RetryList;
- PromoteMem2Reg(Allocas, RetryList, DT, DF, AST).run();
-
- // PromoteMem2Reg may not have been able to promote all of the allocas in one
- // pass, run it again if needed.
- std::vector<AllocaInst*> NewAllocas;
- while (!RetryList.empty()) {
- // If we need to retry some allocas, this is due to there being no store
- // before a read in a local block. To counteract this, insert a store of
- // undef into the alloca right after the alloca itself.
- for (unsigned i = 0, e = RetryList.size(); i != e; ++i) {
- BasicBlock::iterator BBI = RetryList[i];
-
- new StoreInst(UndefValue::get(RetryList[i]->getAllocatedType()),
- RetryList[i], ++BBI);
- }
-
- NewAllocas.assign(RetryList.begin(), RetryList.end());
- RetryList.clear();
- PromoteMem2Reg(NewAllocas, RetryList, DT, DF, AST).run();
- NewAllocas.clear();
- }
+ PromoteMem2Reg(Allocas, DT, DF, AST).run();
}
projects / oota-llvm.git / blobdiff