#include "llvm/BasicBlock.h"
#include "llvm/ConstantVals.h"
-using namespace std;
+using std::vector;
+using std::map;
+using std::set;
namespace {
+ struct PromotePass : public FunctionPass {
+ vector<AllocaInst*> Allocas; // the alloca instruction..
+ map<Instruction*, unsigned> AllocaLookup; // reverse mapping of above
+
+ vector<vector<BasicBlock*> > PhiNodes; // index corresponds to Allocas
+
+ // List of instructions to remove at end of pass
+ vector<Instruction *> KillList;
+
+ map<BasicBlock*,vector<PHINode*> > NewPhiNodes; // the PhiNodes we're adding
-// instance of the promoter -- to keep all the local function data.
-// gets re-created for each function processed
-class PromoteInstance {
-protected:
- vector<AllocaInst*> Allocas; // the alloca instruction..
- map<Instruction*, unsigned> AllocaLookup; // reverse mapping of above
-
- vector<vector<BasicBlock*> > WriteSets; // index corresponds to Allocas
- vector<vector<BasicBlock*> > PhiNodes; // index corresponds to Allocas
- vector<vector<Value*> > CurrentValue; // the current value stack
-
- //list of instructions to remove at end of pass :)
- vector<Instruction *> KillList;
-
- set<BasicBlock*> visited; // the basic blocks we've already visited
- map<BasicBlock*, vector<PHINode*> > NewPhiNodes; // the phinodes we're adding
-
- void traverse(BasicBlock *f, BasicBlock * predecessor);
- bool PromoteFunction(Function *F, DominanceFrontier &DF);
- bool QueuePhiNode(BasicBlock *bb, unsigned alloca_index);
- void findSafeAllocas(Function *M);
- bool didchange;
-public:
- // I do this so that I can force the deconstruction of the local variables
- PromoteInstance(Function *F, DominanceFrontier &DF) {
- didchange = PromoteFunction(F, DF);
- }
- //This returns whether the pass changes anything
- operator bool () { return didchange; }
-};
+ public:
+ // runOnFunction - To run this pass, first we calculate the alloca
+ // instructions that are safe for promotion, then we promote each one.
+ //
+ virtual bool runOnFunction(Function *F);
+
+ // getAnalysisUsage - We need dominance frontiers
+ //
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired(DominanceFrontier::ID);
+ }
+
+ private:
+ void Traverse(BasicBlock *BB, BasicBlock *Pred, vector<Value*> &IncVals,
+ set<BasicBlock*> &Visited);
+ bool QueuePhiNode(BasicBlock *BB, unsigned AllocaIdx);
+ void FindSafeAllocas(Function *F);
+ };
} // end of anonymous namespace
+// isSafeAlloca - This predicate controls what types of alloca instructions are
+// allowed to be promoted...
+//
+static inline bool isSafeAlloca(const AllocaInst *AI) {
+ if (AI->isArrayAllocation()) return false;
+
+ for (Value::use_const_iterator UI = AI->use_begin(), UE = AI->use_end();
+ UI != UE; ++UI) { // Loop over all of the uses of the alloca
+
+ // Only allow nonindexed memory access instructions...
+ if (MemAccessInst *MAI = dyn_cast<MemAccessInst>(*UI)) {
+ if (MAI->hasIndices()) { // indexed?
+ // Allow the access if there is only one index and the index is
+ // zero.
+ if (*MAI->idx_begin() != ConstantUInt::get(Type::UIntTy, 0) ||
+ MAI->idx_begin()+1 != MAI->idx_end())
+ return false;
+ }
+ } else {
+ return false; // Not a load or store?
+ }
+ }
+
+ return true;
+}
-// findSafeAllocas - Find allocas that are safe to promote
+// FindSafeAllocas - Find allocas that are safe to promote
//
-void PromoteInstance::findSafeAllocas(Function *F) {
+void PromotePass::FindSafeAllocas(Function *F) {
BasicBlock *BB = F->getEntryNode(); // Get the entry node for the function
// Look at all instructions in the entry node
for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
if (AllocaInst *AI = dyn_cast<AllocaInst>(*I)) // Is it an alloca?
- if (!AI->isArrayAllocation()) {
- bool isSafe = true;
- for (Value::use_iterator UI = AI->use_begin(), UE = AI->use_end();
- UI != UE; ++UI) { // Loop over all of the uses of the alloca
-
- // Only allow nonindexed memory access instructions...
- if (MemAccessInst *MAI = dyn_cast<MemAccessInst>(*UI)) {
- if (MAI->hasIndices()) { // indexed?
- // Allow the access if there is only one index and the index is
- // zero.
- if (*MAI->idx_begin() != ConstantUInt::get(Type::UIntTy, 0) ||
- MAI->idx_begin()+1 != MAI->idx_end()) {
- isSafe = false;
- break;
- }
- }
- } else {
- isSafe = false; break; // Not a load or store?
- }
- }
- if (isSafe) { // If all checks pass, add alloca to safe list
- AllocaLookup[AI] = Allocas.size();
- Allocas.push_back(AI);
- }
+ if (isSafeAlloca(AI)) { // If safe alloca, add alloca to safe list
+ AllocaLookup[AI] = Allocas.size(); // Keep reverse mapping
+ Allocas.push_back(AI);
}
}
-bool PromoteInstance::PromoteFunction(Function *F, DominanceFrontier &DF) {
+bool PromotePass::runOnFunction(Function *F) {
// Calculate the set of safe allocas
- findSafeAllocas(F);
+ FindSafeAllocas(F);
+
+ // If there is nothing to do, bail out...
+ if (Allocas.empty()) return false;
// Add each alloca to the KillList. Note: KillList is destroyed MOST recently
// added to least recently.
// Calculate the set of write-locations for each alloca. This is analogous to
// counting the number of 'redefinitions' of each variable.
+ vector<vector<BasicBlock*> > WriteSets; // index corresponds to Allocas
WriteSets.resize(Allocas.size());
for (unsigned i = 0; i != Allocas.size(); ++i) {
AllocaInst *AI = Allocas[i];
WriteSets[i].push_back(SI->getParent());
}
+ // Get dominance frontier information...
+ DominanceFrontier &DF = getAnalysis<DominanceFrontier>();
+
// Compute the locations where PhiNodes need to be inserted. Look at the
// dominance frontier of EACH basic-block we have a write in
//
}
}
+ // Set the incoming values for the basic block to be null values for all of
+ // the alloca's. We do this in case there is a load of a value that has not
+ // been stored yet. In this case, it will get this null value.
+ //
+ vector<Value *> Values(Allocas.size());
+ for (unsigned i = 0, e = Allocas.size(); i != e; ++i)
+ Values[i] = Constant::getNullValue(Allocas[i]->getType()->getElementType());
+
// Walks all basic blocks in the function performing the SSA rename algorithm
// and inserting the phi nodes we marked as necessary
//
- CurrentValue.push_back(vector<Value *>(Allocas.size()));
- traverse(F->front(), 0); // there is no predecessor of the root node
+ set<BasicBlock*> Visited; // The basic blocks we've already visited
+ Traverse(F->front(), 0, Values, Visited);
// Remove all instructions marked by being placed in the KillList...
//
Instruction *I = KillList.back();
KillList.pop_back();
- //now go find..
I->getParent()->getInstList().remove(I);
delete I;
}
- return !Allocas.empty();
+ // Purge data structurse so they are available the next iteration...
+ Allocas.clear();
+ AllocaLookup.clear();
+ PhiNodes.clear();
+ NewPhiNodes.clear();
+ return true;
}
// 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
//
-bool PromoteInstance::QueuePhiNode(BasicBlock *BB, unsigned i /*the alloca*/) {
+bool PromotePass::QueuePhiNode(BasicBlock *BB, unsigned AllocaNo) {
// Look up the basic-block in question
vector<PHINode*> &BBPNs = NewPhiNodes[BB];
if (BBPNs.empty()) BBPNs.resize(Allocas.size());
// If the BB already has a phi node added for the i'th alloca then we're done!
- if (BBPNs[i]) return false;
+ if (BBPNs[AllocaNo]) return false;
- // Create a phi-node using the dereferenced type...
- PHINode *PN = new PHINode(Allocas[i]->getType()->getElementType(),
- Allocas[i]->getName()+".mem2reg");
- BBPNs[i] = PN;
+ // Create a PhiNode using the dereferenced type...
+ PHINode *PN = new PHINode(Allocas[AllocaNo]->getType()->getElementType(),
+ Allocas[AllocaNo]->getName()+".mem2reg");
+ BBPNs[AllocaNo] = PN;
// Add the phi-node to the basic-block
BB->getInstList().push_front(PN);
- PhiNodes[i].push_back(BB);
+ PhiNodes[AllocaNo].push_back(BB);
return true;
}
-void PromoteInstance::traverse(BasicBlock *BB, BasicBlock *Pred) {
- vector<Value *> &TOS = CurrentValue.back(); // look at top
-
+void PromotePass::Traverse(BasicBlock *BB, BasicBlock *Pred,
+ vector<Value*> &IncomingVals,
+ set<BasicBlock*> &Visited) {
// If this is a BB needing a phi node, lookup/create the phinode for each
// variable we need phinodes for.
vector<PHINode *> &BBPNs = NewPhiNodes[BB];
for (unsigned k = 0; k != BBPNs.size(); ++k)
- if (BBPNs[k]) {
+ if (PHINode *PN = BBPNs[k]) {
// at this point we can assume that the array has phi nodes.. let's add
// the incoming data
- BBPNs[k]->addIncoming(TOS[k], Pred);
+ PN->addIncoming(IncomingVals[k], Pred);
// also note that the active variable IS designated by the phi node
- TOS[k] = BBPNs[k];
+ IncomingVals[k] = PN;
}
// don't revisit nodes
- if (visited.count(BB)) return;
+ if (Visited.count(BB)) return;
// mark as visited
- visited.insert(BB);
+ Visited.insert(BB);
// keep track of the value of each variable we're watching.. how?
for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II) {
Value *Ptr = LI->getPointerOperand();
if (AllocaInst *Src = dyn_cast<AllocaInst>(Ptr)) {
- map<Instruction*, unsigned>::iterator ai = AllocaLookup.find(Src);
- if (ai != AllocaLookup.end()) {
- Value *V = TOS[ai->second];
+ map<Instruction*, unsigned>::iterator AI = AllocaLookup.find(Src);
+ if (AI != AllocaLookup.end()) {
+ Value *V = IncomingVals[AI->second];
// walk the use list of this load and replace all uses with r
LI->replaceAllUsesWith(V);
map<Instruction *, unsigned>::iterator ai = AllocaLookup.find(Dest);
if (ai != AllocaLookup.end()) {
// what value were we writing?
- TOS[ai->second] = SI->getOperand(0);
+ IncomingVals[ai->second] = SI->getOperand(0);
KillList.push_back(SI); // Mark the store to be deleted
}
}
} else if (TerminatorInst *TI = dyn_cast<TerminatorInst>(I)) {
// Recurse across our successors
for (unsigned i = 0; i != TI->getNumSuccessors(); i++) {
- CurrentValue.push_back(CurrentValue.back());
- traverse(TI->getSuccessor(i), BB); // This node becomes the predecessor
- CurrentValue.pop_back();
+ vector<Value*> OutgoingVals(IncomingVals);
+ Traverse(TI->getSuccessor(i), BB, OutgoingVals, Visited);
}
}
}
}
-namespace {
- struct PromotePass : public FunctionPass {
-
- // runOnFunction - To run this pass, first we calculate the alloca
- // instructions that are safe for promotion, then we promote each one.
- //
- virtual bool runOnFunction(Function *F) {
- return (bool)PromoteInstance(F, getAnalysis<DominanceFrontier>());
- }
-
- // getAnalysisUsage - We need dominance frontiers
- //
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired(DominanceFrontier::ID);
- }
- };
-}
-
-
// createPromoteMemoryToRegister - Provide an entry point to create this pass.
//
Pass *createPromoteMemoryToRegister() {
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