#include "llvm/Pass.h"
#include "llvm/Function.h"
#include "llvm/BasicBlock.h"
-#include "llvm/ConstantVals.h"
+#include "llvm/Constant.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
-using cfg::DominanceFrontier;
+ public:
+ const char *getPassName() const { return "Promote Memory to Register"; }
-namespace {
+ // 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);
-//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 *, int> 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 *> > new_phinodes; //the phinodes we're adding
-
-
- void traverse(BasicBlock *f, BasicBlock * predecessor);
- bool PromoteFunction(Function *F, DominanceFrontier &DF);
- bool queuePhiNode(BasicBlock *bb, int 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; }
-};
+ // getAnalysisUsage - We need dominance frontiers
+ //
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired(DominanceFrontier::ID);
+ AU.preservesCFG();
+ }
+
+ 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
-// findSafeAllocas - Find allocas that are safe to promote
+
+// isSafeAlloca - This predicate controls what types of alloca instructions are
+// allowed to be promoted...
//
-void PromoteInstance::findSafeAllocas(Function *F)
-{
+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() != Constant::getNullValue(Type::UIntTy) ||
+ 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
+//
+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) {
- // Calculate the set of safe allocas
- findSafeAllocas(F);
-
- // Add each alloca to the killlist
- // note: killlist is destroyed MOST recently added to least recently.
- killlist.assign(Allocas.begin(), Allocas.end());
-
- // Calculate the set of write-locations for each alloca.
- // this is analogous to counting the number of 'redefinitions' of each variable.
- for (unsigned i = 0; i<Allocas.size(); ++i)
- {
- AllocaInst * AI = Allocas[i];
- WriteSets.push_back(std::vector<BasicBlock *>()); //add a new set
- for (Value::use_iterator U = AI->use_begin();U!=AI->use_end();++U)
- {
- if (MemAccessInst *MAI = dyn_cast<StoreInst>(*U)) {
- WriteSets[i].push_back(MAI->getParent()); // jot down the basic-block it came from
- }
- }
- }
-
- // Compute the locations where PhiNodes need to be inserted
- // look at the dominance frontier of EACH basic-block we have a write in
- PhiNodes.resize(Allocas.size());
- for (unsigned i = 0; i<Allocas.size(); ++i)
- {
- for (unsigned j = 0; j<WriteSets[i].size(); j++)
- {
- //look up the DF for this write, add it to PhiNodes
- DominanceFrontier::const_iterator it = DF.find(WriteSets[i][j]);
- DominanceFrontier::DomSetType s = (*it).second;
- for (DominanceFrontier::DomSetType::iterator p = s.begin();p!=s.end(); ++p)
- {
- if (queuePhiNode((BasicBlock *)*p, i))
- PhiNodes[i].push_back((BasicBlock *)*p);
- }
- }
- // perform iterative step
- for (unsigned k = 0; k<PhiNodes[i].size(); k++)
- {
- DominanceFrontier::const_iterator it = DF.find(PhiNodes[i][k]);
- DominanceFrontier::DomSetType s = it->second;
- for (DominanceFrontier::DomSetType::iterator p = s.begin(); p!=s.end(); ++p)
- {
- if (queuePhiNode((BasicBlock *)*p,i))
- PhiNodes[i].push_back((BasicBlock*)*p);
- }
- }
- }
-
- // Walks all basic blocks in the function
- // performing the SSA rename algorithm
- // and inserting the phi nodes we marked as necessary
- BasicBlock * f = F->front(); //get root basic-block
-
- CurrentValue.push_back(vector<Value *>(Allocas.size()));
-
- traverse(f, NULL); // there is no predecessor of the root node
-
-
- // ** REMOVE EVERYTHING IN THE KILL-LIST **
- // we need to kill 'uses' before root values
- // so we should probably run through in reverse
- for (vector<Instruction *>::reverse_iterator i = killlist.rbegin(); i!=killlist.rend(); ++i)
- {
- Instruction * r = *i;
- BasicBlock * o = r->getParent();
- //now go find..
-
- BasicBlock::InstListType & l = o->getInstList();
- o->getInstList().remove(r);
- delete r;
- }
-
- return !Allocas.empty();
+bool PromotePass::runOnFunction(Function *F) {
+ // Calculate the set of safe allocas
+ 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.
+ KillList.assign(Allocas.begin(), Allocas.end());
+
+ // 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];
+ for (Value::use_iterator U =AI->use_begin(), E = AI->use_end(); U != E; ++U)
+ if (StoreInst *SI = dyn_cast<StoreInst>(*U))
+ // jot down the basic-block it came from
+ 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
+ //
+ PhiNodes.resize(Allocas.size());
+ for (unsigned i = 0; i != Allocas.size(); ++i) {
+ for (unsigned j = 0; j != WriteSets[i].size(); j++) {
+ // Look up the DF for this write, add it to PhiNodes
+ DominanceFrontier::const_iterator it = DF.find(WriteSets[i][j]);
+ DominanceFrontier::DomSetType S = it->second;
+ for (DominanceFrontier::DomSetType::iterator P = S.begin(), PE = S.end();
+ P != PE; ++P)
+ QueuePhiNode(*P, i);
+ }
+
+ // Perform iterative step
+ for (unsigned k = 0; k != PhiNodes[i].size(); k++) {
+ DominanceFrontier::const_iterator it = DF.find(PhiNodes[i][k]);
+ DominanceFrontier::DomSetType S = it->second;
+ for (DominanceFrontier::DomSetType::iterator P = S.begin(), PE = S.end();
+ P != PE; ++P)
+ QueuePhiNode(*P, i);
+ }
+ }
+
+ // 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
+ //
+ 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...
+ //
+ while (!KillList.empty()) {
+ Instruction *I = KillList.back();
+ KillList.pop_back();
+
+ I->getParent()->getInstList().remove(I);
+ delete I;
+ }
+
+ // 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 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());
-void PromoteInstance::traverse(BasicBlock *f, BasicBlock * predecessor)
-{
- vector<Value *> * tos = &CurrentValue.back(); //look at top-
-
- //if this is a BB needing a phi node, lookup/create the phinode for
- // each variable we need phinodes for.
- map<BasicBlock *, vector<PHINode *> >::iterator nd = new_phinodes.find(f);
- if (nd!=new_phinodes.end())
- {
- for (unsigned k = 0; k!=nd->second.size(); ++k)
- if (nd->second[k])
- {
- //at this point we can assume that the array has phi nodes.. let's
- // add the incoming data
- if ((*tos)[k])
- nd->second[k]->addIncoming((*tos)[k],predecessor);
- //also note that the active variable IS designated by the phi node
- (*tos)[k] = nd->second[k];
- }
- }
-
- //don't revisit nodes
- if (visited.find(f)!=visited.end())
- return;
- //mark as visited
- visited.insert(f);
-
- BasicBlock::iterator i = f->begin();
- //keep track of the value of each variable we're watching.. how?
- while(i!=f->end())
- {
- Instruction * inst = *i; //get the instruction
- //is this a write/read?
- if (LoadInst * LI = dyn_cast<LoadInst>(inst))
- {
- // This is a bit weird...
- Value * ptr = LI->getPointerOperand(); //of type value
- if (AllocaInst * srcinstr = dyn_cast<AllocaInst>(ptr))
- {
- map<Instruction *, int>::iterator ai = AllocaLookup.find(srcinstr);
- if (ai!=AllocaLookup.end())
- {
- if (Value *r = (*tos)[ai->second])
- {
- //walk the use list of this load and replace
- // all uses with r
- LI->replaceAllUsesWith(r);
- //now delete the instruction.. somehow..
- killlist.push_back((Instruction *)LI);
- }
- }
- }
- }
- else if (StoreInst * SI = dyn_cast<StoreInst>(inst))
- {
- // delete this instruction and mark the name as the
- // current holder of the value
- Value * ptr = SI->getPointerOperand(); //of type value
- if (Instruction * srcinstr = dyn_cast<Instruction>(ptr))
- {
- map<Instruction *, int>::iterator ai = AllocaLookup.find(srcinstr);
- if (ai!=AllocaLookup.end())
- {
- //what value were we writing?
- Value * writeval = SI->getOperand(0);
- //write down...
- (*tos)[ai->second] = writeval;
- //now delete it.. somehow?
- killlist.push_back((Instruction *)SI);
- }
- }
-
- }
- else if (TerminatorInst * TI = dyn_cast<TerminatorInst>(inst))
- {
- // Recurse across our sucessors
- for (unsigned i = 0; i!=TI->getNumSuccessors(); i++)
- {
- CurrentValue.push_back(CurrentValue.back());
- traverse(TI->getSuccessor(i),f); //this node IS the predecessor
- CurrentValue.pop_back();
- }
- }
- i++;
- }
-}
+ // If the BB already has a phi node added for the i'th alloca then we're done!
+ if (BBPNs[AllocaNo]) return false;
-// 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, int i /*the alloca*/)
-{
- map<BasicBlock *, vector<PHINode *> >::iterator nd;
- //look up the basic-block in question
- nd = new_phinodes.find(bb);
- //if the basic-block has no phi-nodes added, or at least none
- //for the i'th alloca. then add.
- if (nd==new_phinodes.end() || nd->second[i]==NULL)
- {
- //we're not added any phi nodes to this basicblock yet
- // create the phi-node array.
- if (nd==new_phinodes.end())
- {
- new_phinodes[bb] = vector<PHINode *>(Allocas.size());
- nd = new_phinodes.find(bb);
- }
-
- //find the type the alloca returns
- const PointerType * pt = Allocas[i]->getType();
- //create a phi-node using the DEREFERENCED type
- PHINode * ph = new PHINode(pt->getElementType(), Allocas[i]->getName()+".mem2reg");
- nd->second[i] = ph;
- //add the phi-node to the basic-block
- bb->getInstList().push_front(ph);
- return true;
- }
- return false;
-}
+ // 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);
-namespace {
- struct PromotePass : public MethodPass {
+ PhiNodes[AllocaNo].push_back(BB);
+ return true;
+}
- // runOnMethod - To run this pass, first we calculate the alloca
- // instructions that are safe for promotion, then we promote each one.
- //
- virtual bool runOnMethod(Function *F) {
- return (bool)PromoteInstance(F, getAnalysis<DominanceFrontier>());
+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 (PHINode *PN = BBPNs[k]) {
+ // at this point we can assume that the array has phi nodes.. let's add
+ // the incoming data
+ PN->addIncoming(IncomingVals[k], Pred);
+
+ // also note that the active variable IS designated by the phi node
+ IncomingVals[k] = PN;
}
-
- // getAnalysisUsageInfo - We need dominance frontiers
- //
- virtual void getAnalysisUsageInfo(Pass::AnalysisSet &Requires,
- Pass::AnalysisSet &Destroyed,
- Pass::AnalysisSet &Provided) {
- Requires.push_back(DominanceFrontier::ID);
+ // don't revisit nodes
+ if (Visited.count(BB)) return;
+
+ // mark as visited
+ 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) {
+ Instruction *I = *II; //get the instruction
+
+ if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
+ 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 = IncomingVals[AI->second];
+
+ // walk the use list of this load and replace all uses with r
+ LI->replaceAllUsesWith(V);
+ KillList.push_back(LI); // Mark the load to be deleted
+ }
+ }
+ } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
+ // delete this instruction and mark the name as the current holder of the
+ // value
+ Value *Ptr = SI->getPointerOperand();
+ if (AllocaInst *Dest = dyn_cast<AllocaInst>(Ptr)) {
+ map<Instruction *, unsigned>::iterator ai = AllocaLookup.find(Dest);
+ if (ai != AllocaLookup.end()) {
+ // what value were we writing?
+ 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++) {
+ vector<Value*> OutgoingVals(IncomingVals);
+ Traverse(TI->getSuccessor(i), BB, OutgoingVals, Visited);
+ }
}
- };
+ }
}
-
+
// createPromoteMemoryToRegister - Provide an entry point to create this pass.
//
Pass *createPromoteMemoryToRegister() {
- return new PromotePass();
+ return new PromotePass();
}
-
-
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