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Generalize LoadAndStorePromoter a bit and switch LICM

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to use it.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123501 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2011-01-15 00:12:35 +00:00
parent ca3f06963c
commit deaf55f698
4 changed files with 131 additions and 193 deletions
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23
include/llvm/Transforms/Utils/SSAUpdater.h
View File

@ -118,15 +118,17 @@ private:
/// virtual methods.
///
class LoadAndStorePromoter {
protected:
SSAUpdater &SSA;
public:
LoadAndStorePromoter() {}
LoadAndStorePromoter(const SmallVectorImpl<Instruction*> &Insts,
SSAUpdater &S, StringRef Name = StringRef());
virtual ~LoadAndStorePromoter() {}
/// run - This does the promotion. Insts is a list of loads and stores to
/// promote, and Name is the basename for the PHIs to insert. After this is
/// complete, the loads and stores are removed from the code.
void run(StringRef Name, const SmallVectorImpl<Instruction*> &Insts,
SSAUpdater *SSA = 0);
void run(const SmallVectorImpl<Instruction*> &Insts) const;
/// Return true if the specified instruction is in the Inst list (which was
@ -139,6 +141,21 @@ public:
return true;
return false;
}
/// doExtraRewritesBeforeFinalDeletion - This hook is invoked after all the
/// stores are found and inserted as available values, but
virtual void doExtraRewritesBeforeFinalDeletion() const {
}
/// replaceLoadWithValue - Clients can choose to implement this to get
/// notified right before a load is RAUW'd another value.
virtual void replaceLoadWithValue(LoadInst *LI, Value *V) const {
}
/// This is called before each instruction is deleted.
virtual void instructionDeleted(Instruction *I) const {
}
};
} // End llvm namespace

229
lib/Transforms/Scalar/LICM.cpp
View File

@ -595,6 +595,53 @@ bool LICM::isSafeToExecuteUnconditionally(Instruction &Inst) {
return true;
}
namespace {
class LoopPromoter : public LoadAndStorePromoter {
Value *SomePtr; // Designated pointer to store to.
SmallPtrSet<Value*, 4> &PointerMustAliases;
SmallVectorImpl<BasicBlock*> &LoopExitBlocks;
AliasSetTracker &AST;
public:
LoopPromoter(Value *SP,
const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S,
SmallPtrSet<Value*, 4> &PMA,
SmallVectorImpl<BasicBlock*> &LEB, AliasSetTracker &ast)
: LoadAndStorePromoter(Insts, S), SomePtr(SP), PointerMustAliases(PMA),
LoopExitBlocks(LEB), AST(ast) {}
virtual bool isInstInList(Instruction *I,
const SmallVectorImpl<Instruction*> &) const {
Value *Ptr;
if (LoadInst *LI = dyn_cast<LoadInst>(I))
Ptr = LI->getOperand(0);
else
Ptr = cast<StoreInst>(I)->getPointerOperand();
return PointerMustAliases.count(Ptr);
}
virtual void doExtraRewritesBeforeFinalDeletion() const {
// Insert stores after in the loop exit blocks. Each exit block gets a
// store of the live-out values that feed them. Since we've already told
// the SSA updater about the defs in the loop and the preheader
// definition, it is all set and we can start using it.
for (unsigned i = 0, e = LoopExitBlocks.size(); i != e; ++i) {
BasicBlock *ExitBlock = LoopExitBlocks[i];
Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
Instruction *InsertPos = ExitBlock->getFirstNonPHI();
new StoreInst(LiveInValue, SomePtr, InsertPos);
}
}
virtual void replaceLoadWithValue(LoadInst *LI, Value *V) const {
// Update alias analysis.
AST.copyValue(LI, V);
}
virtual void instructionDeleted(Instruction *I) const {
AST.deleteValue(I);
}
};
} // end anon namespace
/// PromoteAliasSet - Try to promote memory values to scalars by sinking
/// stores out of the loop and moving loads to before the loop. We do this by
/// looping over the stores in the loop, looking for stores to Must pointers
@ -679,179 +726,43 @@ void LICM::PromoteAliasSet(AliasSet &AS) {
Changed = true;
++NumPromoted;
SmallVector<BasicBlock*, 8> ExitBlocks;
CurLoop->getUniqueExitBlocks(ExitBlocks);
// We use the SSAUpdater interface to insert phi nodes as required.
SmallVector<PHINode*, 16> NewPHIs;
SSAUpdater SSA(&NewPHIs);
LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks,
*CurAST);
// It wants to know some value of the same type as what we'll be inserting.
Value *SomeValue;
if (isa<LoadInst>(LoopUses[0]))
SomeValue = LoopUses[0];
else
SomeValue = cast<StoreInst>(LoopUses[0])->getOperand(0);
SSA.Initialize(SomeValue->getType(), SomeValue->getName());
// First step: bucket up uses of the pointers by the block they occur in.
// This is important because we have to handle multiple defs/uses in a block
// ourselves: SSAUpdater is purely for cross-block references.
// FIXME: Want a TinyVector<Instruction*> since there is usually 0/1 element.
DenseMap<BasicBlock*, std::vector<Instruction*> > UsesByBlock;
for (unsigned i = 0, e = LoopUses.size(); i != e; ++i) {
Instruction *User = LoopUses[i];
UsesByBlock[User->getParent()].push_back(User);
}
// Okay, now we can iterate over all the blocks in the loop with uses,
// processing them. Keep track of which loads are loading a live-in value.
SmallVector<LoadInst*, 32> LiveInLoads;
DenseMap<Value*, Value*> ReplacedLoads;
for (unsigned LoopUse = 0, e = LoopUses.size(); LoopUse != e; ++LoopUse) {
Instruction *User = LoopUses[LoopUse];
std::vector<Instruction*> &BlockUses = UsesByBlock[User->getParent()];
// If this block has already been processed, ignore this repeat use.
if (BlockUses.empty()) continue;
// Okay, this is the first use in the block. If this block just has a
// single user in it, we can rewrite it trivially.
if (BlockUses.size() == 1) {
// If it is a store, it is a trivial def of the value in the block.
if (isa<StoreInst>(User)) {
SSA.AddAvailableValue(User->getParent(),
cast<StoreInst>(User)->getOperand(0));
} else {
// Otherwise it is a load, queue it to rewrite as a live-in load.
LiveInLoads.push_back(cast<LoadInst>(User));
}
BlockUses.clear();
continue;
}
// Otherwise, check to see if this block is all loads. If so, we can queue
// them all as live in loads.
bool HasStore = false;
for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) {
if (isa<StoreInst>(BlockUses[i])) {
HasStore = true;
break;
}
}
if (!HasStore) {
for (unsigned i = 0, e = BlockUses.size(); i != e; ++i)
LiveInLoads.push_back(cast<LoadInst>(BlockUses[i]));
BlockUses.clear();
continue;
}
// Otherwise, we have mixed loads and stores (or just a bunch of stores).
// Since SSAUpdater is purely for cross-block values, we need to determine
// the order of these instructions in the block. If the first use in the
// block is a load, then it uses the live in value. The last store defines
// the live out value. We handle this by doing a linear scan of the block.
BasicBlock *BB = User->getParent();
Value *StoredValue = 0;
for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
if (LoadInst *L = dyn_cast<LoadInst>(II)) {
// If this is a load from an unrelated pointer, ignore it.
if (!PointerMustAliases.count(L->getOperand(0))) continue;
// If we haven't seen a store yet, this is a live in use, otherwise
// use the stored value.
if (StoredValue) {
L->replaceAllUsesWith(StoredValue);
ReplacedLoads[L] = StoredValue;
} else {
LiveInLoads.push_back(L);
}
continue;
}
if (StoreInst *S = dyn_cast<StoreInst>(II)) {
// If this is a store to an unrelated pointer, ignore it.
if (!PointerMustAliases.count(S->getOperand(1))) continue;
// Remember that this is the active value in the block.
StoredValue = S->getOperand(0);
}
}
// The last stored value that happened is the live-out for the block.
assert(StoredValue && "Already checked that there is a store in block");
SSA.AddAvailableValue(BB, StoredValue);
BlockUses.clear();
}
// Now that all the intra-loop values are classified, set up the preheader.
// It gets a load of the pointer we're promoting, and it is the live-out value
// from the preheader.
LoadInst *PreheaderLoad = new LoadInst(SomePtr,SomePtr->getName()+".promoted",
Preheader->getTerminator());
// Set up the preheader to have a definition of the value. It is the live-out
// value from the preheader that uses in the loop will use.
LoadInst *PreheaderLoad =
new LoadInst(SomePtr, SomePtr->getName()+".promoted",
Preheader->getTerminator());
SSA.AddAvailableValue(Preheader, PreheaderLoad);
// Now that the preheader is good to go, set up the exit blocks. Each exit
// block gets a store of the live-out values that feed them. Since we've
// already told the SSA updater about the defs in the loop and the preheader
// definition, it is all set and we can start using it.
SmallVector<BasicBlock*, 8> ExitBlocks;
CurLoop->getUniqueExitBlocks(ExitBlocks);
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
BasicBlock *ExitBlock = ExitBlocks[i];
Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
Instruction *InsertPos = ExitBlock->getFirstNonPHI();
new StoreInst(LiveInValue, SomePtr, InsertPos);
// Copy any value stored to or loaded from a must-alias of the pointer.
if (PreheaderLoad->getType()->isPointerTy()) {
Value *SomeValue;
if (LoadInst *LI = dyn_cast<LoadInst>(LoopUses[0]))
SomeValue = LI;
else
SomeValue = cast<StoreInst>(LoopUses[0])->getValueOperand();
CurAST->copyValue(SomeValue, PreheaderLoad);
}
// Okay, now we rewrite all loads that use live-in values in the loop,
// inserting PHI nodes as necessary.
for (unsigned i = 0, e = LiveInLoads.size(); i != e; ++i) {
LoadInst *ALoad = LiveInLoads[i];
Value *NewVal = SSA.GetValueInMiddleOfBlock(ALoad->getParent());
ALoad->replaceAllUsesWith(NewVal);
CurAST->copyValue(ALoad, NewVal);
ReplacedLoads[ALoad] = NewVal;
}
// Rewrite all the loads in the loop and remember all the definitions from
// stores in the loop.
Promoter.run(LoopUses);
// If the preheader load is itself a pointer, we need to tell alias analysis
// about the new pointer we created in the preheader block and about any PHI
// nodes that just got inserted.
if (PreheaderLoad->getType()->isPointerTy()) {
// Copy any value stored to or loaded from a must-alias of the pointer.
CurAST->copyValue(SomeValue, PreheaderLoad);
for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
CurAST->copyValue(SomeValue, NewPHIs[i]);
}
// Now that everything is rewritten, delete the old instructions from the body
// of the loop. They should all be dead now.
for (unsigned i = 0, e = LoopUses.size(); i != e; ++i) {
Instruction *User = LoopUses[i];
// If this is a load that still has uses, then the load must have been added
// as a live value in the SSAUpdate data structure for a block (e.g. because
// the loaded value was stored later). In this case, we need to recursively
// propagate the updates until we get to the real value.
if (!User->use_empty()) {
Value *NewVal = ReplacedLoads[User];
assert(NewVal && "not a replaced load?");
// Propagate down to the ultimate replacee. The intermediately loads
// could theoretically already have been deleted, so we don't want to
// dereference the Value*'s.
DenseMap<Value*, Value*>::iterator RLI = ReplacedLoads.find(NewVal);
while (RLI != ReplacedLoads.end()) {
NewVal = RLI->second;
RLI = ReplacedLoads.find(NewVal);
}
User->replaceAllUsesWith(NewVal);
CurAST->copyValue(User, NewVal);
}
CurAST->deleteValue(User);
User->eraseFromParent();
CurAST->copyValue(PreheaderLoad, NewPHIs[i]);
}
// fwew, we're done!

31
lib/Transforms/Scalar/ScalarReplAggregates.cpp
View File

@ -844,20 +844,13 @@ namespace {
class AllocaPromoter : public LoadAndStorePromoter {
AllocaInst *AI;
public:
AllocaPromoter() : AI(0) {}
AllocaPromoter(const SmallVectorImpl<Instruction*> &Insts, SSAUpdater &S)
: LoadAndStorePromoter(Insts, S), AI(0) {}
void run(AllocaInst *AI, SSAUpdater &SSA) {
void run(AllocaInst *AI, const SmallVectorImpl<Instruction*> &Insts) {
// Remember which alloca we're promoting (for isInstInList).
this->AI = AI;
// Build the list of instructions to promote.
SmallVector<Instruction*, 64> Insts;
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
UI != E; ++UI)
Insts.push_back(cast<Instruction>(*UI));
LoadAndStorePromoter::run(AI->getName(), Insts, &SSA);
LoadAndStorePromoter::run(Insts);
AI->eraseFromParent();
}
@ -882,7 +875,7 @@ bool SROA::performPromotion(Function &F) {
BasicBlock &BB = F.getEntryBlock(); // Get the entry node for the function
bool Changed = false;
SmallVector<Instruction*, 64> Insts;
while (1) {
Allocas.clear();
@ -899,9 +892,17 @@ bool SROA::performPromotion(Function &F) {
PromoteMemToReg(Allocas, *DT, *DF);
else {
SSAUpdater SSA;
AllocaPromoter Promoter;
for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
Promoter.run(Allocas[i], SSA);
for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
AllocaInst *AI = Allocas[i];
// Build list of instructions to promote.
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
UI != E; ++UI)
Insts.push_back(cast<Instruction>(*UI));
AllocaPromoter(Insts, SSA).run(AI, Insts);
Insts.clear();
}
}
NumPromoted += Allocas.size();
Changed = true;

41
lib/Transforms/Utils/SSAUpdater.cpp
View File

@ -348,23 +348,25 @@ Value *SSAUpdater::GetValueAtEndOfBlockInternal(BasicBlock *BB) {
// LoadAndStorePromoter Implementation
//===----------------------------------------------------------------------===//
void LoadAndStorePromoter::run(StringRef BaseName,
const SmallVectorImpl<Instruction*> &Insts,
SSAUpdater *SSA) {
LoadAndStorePromoter::
LoadAndStorePromoter(const SmallVectorImpl<Instruction*> &Insts,
SSAUpdater &S, StringRef BaseName) : SSA(S) {
if (Insts.empty()) return;
// If no SSAUpdater was provided, use a default one. This allows the client
// to capture inserted PHI nodes etc if they want.
SSAUpdater DefaultSSA;
if (SSA == 0) SSA = &DefaultSSA;
const Type *ValTy;
Value *SomeVal;
if (LoadInst *LI = dyn_cast<LoadInst>(Insts[0]))
ValTy = LI->getType();
SomeVal = LI;
else
ValTy = cast<StoreInst>(Insts[0])->getOperand(0)->getType();
SSA->Initialize(ValTy, BaseName);
SomeVal = cast<StoreInst>(Insts[0])->getOperand(0);
if (BaseName.empty())
BaseName = SomeVal->getName();
SSA.Initialize(SomeVal->getType(), BaseName);
}
void LoadAndStorePromoter::
run(const SmallVectorImpl<Instruction*> &Insts) const {
// First step: bucket up uses of the alloca by the block they occur in.
// This is important because we have to handle multiple defs/uses in a block
@ -396,7 +398,7 @@ void LoadAndStorePromoter::run(StringRef BaseName,
if (BlockUses.size() == 1) {
// If it is a store, it is a trivial def of the value in the block.
if (StoreInst *SI = dyn_cast<StoreInst>(User))
SSA->AddAvailableValue(BB, SI->getOperand(0));
SSA.AddAvailableValue(BB, SI->getOperand(0));
else
// Otherwise it is a load, queue it to rewrite as a live-in load.
LiveInLoads.push_back(cast<LoadInst>(User));
@ -437,6 +439,7 @@ void LoadAndStorePromoter::run(StringRef BaseName,
// If we haven't seen a store yet, this is a live in use, otherwise
// use the stored value.
if (StoredValue) {
replaceLoadWithValue(L, StoredValue);
L->replaceAllUsesWith(StoredValue);
ReplacedLoads[L] = StoredValue;
} else {
@ -456,7 +459,7 @@ void LoadAndStorePromoter::run(StringRef BaseName,
// The last stored value that happened is the live-out for the block.
assert(StoredValue && "Already checked that there is a store in block");
SSA->AddAvailableValue(BB, StoredValue);
SSA.AddAvailableValue(BB, StoredValue);
BlockUses.clear();
}
@ -464,11 +467,15 @@ void LoadAndStorePromoter::run(StringRef BaseName,
// inserting PHI nodes as necessary.
for (unsigned i = 0, e = LiveInLoads.size(); i != e; ++i) {
LoadInst *ALoad = LiveInLoads[i];
Value *NewVal = SSA->GetValueInMiddleOfBlock(ALoad->getParent());
Value *NewVal = SSA.GetValueInMiddleOfBlock(ALoad->getParent());
replaceLoadWithValue(ALoad, NewVal);
ALoad->replaceAllUsesWith(NewVal);
ReplacedLoads[ALoad] = NewVal;
}
// Allow the client to do stuff before we start nuking things.
doExtraRewritesBeforeFinalDeletion();
// Now that everything is rewritten, delete the old instructions from the
// function. They should all be dead now.
for (unsigned i = 0, e = Insts.size(); i != e; ++i) {
@ -491,9 +498,11 @@ void LoadAndStorePromoter::run(StringRef BaseName,
RLI = ReplacedLoads.find(NewVal);
}
replaceLoadWithValue(cast<LoadInst>(User), NewVal);
User->replaceAllUsesWith(NewVal);
}
instructionDeleted(User);
User->eraseFromParent();
}
}