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switch SRoA to use LoadAndStorePromoter instead of its own copy of the code.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123457 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2011-01-14 19:50:47 +00:00
parent a2d845a3ff
commit d0f56132cf
1 changed files with 28 additions and 138 deletions
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166
lib/Transforms/Scalar/ScalarReplAggregates.cpp
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@ -840,144 +840,35 @@ bool SROA::runOnFunction(Function &F) {
return Changed;
}
/// PromoteAlloca - Promote an alloca to registers, using SSAUpdater.
static void PromoteAlloca(AllocaInst *AI, SSAUpdater &SSA) {
SSA.Initialize(AI->getType()->getElementType(), AI->getName());
namespace {
class AllocaPromoter : public LoadAndStorePromoter {
AllocaInst *AI;
public:
AllocaPromoter() : AI(0) {}
void run(AllocaInst *AI, SSAUpdater &SSA) {
// Remember which alloca we're promoting (for isInstInList).
this->AI = AI;
// 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
// ourselves: SSAUpdater is purely for cross-block references.
// FIXME: Want a TinyVector<Instruction*> since there is often 0/1 element.
DenseMap<BasicBlock*, std::vector<Instruction*> > UsesByBlock;
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
UsesByBlock[User->getParent()].push_back(User);
// 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);
AI->eraseFromParent();
}
// Okay, now we can iterate over all the blocks in the function with uses,
// processing them. Keep track of which loads are loading a live-in value.
// Walk the uses in the use-list order to be determinstic.
SmallVector<LoadInst*, 32> LiveInLoads;
DenseMap<Value*, Value*> ReplacedLoads;
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end();
UI != E; ++UI) {
Instruction *User = cast<Instruction>(*UI);
BasicBlock *BB = User->getParent();
std::vector<Instruction*> &BlockUses = UsesByBlock[BB];
// 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 (StoreInst *SI = dyn_cast<StoreInst>(User))
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));
BlockUses.clear();
continue;
}
// Otherwise, check to see if this block is all loads.
bool HasStore = false;
for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) {
if (isa<StoreInst>(BlockUses[i])) {
HasStore = true;
break;
}
}
// If so, we can queue them all as live in loads. We don't have an
// efficient way to tell which on is first in the block and don't want to
// scan large blocks, so just add all loads as live ins.
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.
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 (L->getOperand(0) != AI) 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 (S->getPointerOperand() != AI) 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();
virtual bool isInstInList(Instruction *I,
const SmallVectorImpl<Instruction*> &Insts) const {
if (LoadInst *LI = dyn_cast<LoadInst>(I))
return LI->getOperand(0) == AI;
return cast<StoreInst>(I)->getPointerOperand() == AI;
}
// 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);
ReplacedLoads[ALoad] = NewVal;
}
// Now that everything is rewritten, delete the old instructions from the
// function. They should all be dead now.
for (Value::use_iterator UI = AI->use_begin(), E = AI->use_end(); UI != E; ) {
Instruction *User = cast<Instruction>(*UI++);
// 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);
}
User->eraseFromParent();
}
}
};
} // end anon namespace
bool SROA::performPromotion(Function &F) {
std::vector<AllocaInst*> Allocas;
@ -1008,10 +899,9 @@ bool SROA::performPromotion(Function &F) {
PromoteMemToReg(Allocas, *DT, *DF);
else {
SSAUpdater SSA;
for (unsigned i = 0, e = Allocas.size(); i != e; ++i) {
PromoteAlloca(Allocas[i], SSA);
Allocas[i]->eraseFromParent();
}
AllocaPromoter Promoter;
for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
Promoter.run(Allocas[i], SSA);
}
NumPromoted += Allocas.size();
Changed = true;