#include "llvm/Transforms/Utils/Local.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/AliasSetTracker.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/Instructions.h"
#include "llvm/DerivedTypes.h"
+#include "llvm/Target/TargetData.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/CFG.h"
-#include "Support/Statistic.h"
#include "Support/CommandLine.h"
+#include "Support/Debug.h"
+#include "Support/Statistic.h"
#include "llvm/Assembly/Writer.h"
#include <algorithm>
Statistic<> NumHoistedLoads("licm", "Number of load insts hoisted");
Statistic<> NumPromoted("licm", "Number of memory locations promoted to registers");
- /// LoopBodyInfo - We recursively traverse loops from most-deeply-nested to
- /// least-deeply-nested. For all of the loops nested within the current one,
- /// we keep track of information so that we don't have to repeat queries.
- ///
- struct LoopBodyInfo {
- std::vector<CallInst*> Calls; // Call instructions in loop
- std::vector<InvokeInst*> Invokes; // Invoke instructions in loop
-
- // StoredPointers - Targets of store instructions...
- std::set<Value*> StoredPointers;
-
- // LoadedPointers - Source pointers for load instructions...
- std::set<Value*> LoadedPointers;
-
- enum PointerClass {
- PointerUnknown = 0, // Nothing is known about this pointer yet
- PointerMustStore, // Memory is stored to ONLY through this pointer
- PointerMayStore, // Memory is stored to through this or other pointers
- PointerNoStore // Memory is not modified in this loop
- };
-
- // PointerIsModified - Keep track of information as we find out about it in
- // the loop body...
- //
- std::map<Value*, enum PointerClass> PointerIsModified;
-
- /// CantModifyAnyPointers - Return true if no memory modifying instructions
- /// occur in this loop. This is just a conservative approximation, because
- /// a call may not actually store anything.
- bool CantModifyAnyPointers() const {
- return Calls.empty() && Invokes.empty() && StoredPointers.empty();
- }
-
- /// incorporate - Incorporate information about a subloop into the current
- /// loop.
- void incorporate(const LoopBodyInfo &OtherLBI);
- void incorporate(BasicBlock &BB); // do the same for a basic block
-
- PointerClass getPointerInfo(Value *V, AliasAnalysis &AA) {
- PointerClass &VInfo = PointerIsModified[V];
- if (VInfo == PointerUnknown)
- VInfo = calculatePointerInfo(V, AA);
- return VInfo;
- }
- private:
- /// calculatePointerInfo - Calculate information about the specified
- /// pointer.
- PointerClass calculatePointerInfo(Value *V, AliasAnalysis &AA) const;
- };
-}
-
-/// incorporate - Incorporate information about a subloop into the current loop.
-void LoopBodyInfo::incorporate(const LoopBodyInfo &OtherLBI) {
- // Do not incorporate NonModifiedPointers (which is just a cache) because it
- // is too much trouble to make sure it's still valid.
- Calls.insert (Calls.end(), OtherLBI.Calls.begin(), OtherLBI.Calls.end());
- Invokes.insert(Invokes.end(),OtherLBI.Invokes.begin(),OtherLBI.Invokes.end());
- StoredPointers.insert(OtherLBI.StoredPointers.begin(),
- OtherLBI.StoredPointers.end());
- LoadedPointers.insert(OtherLBI.LoadedPointers.begin(),
- OtherLBI.LoadedPointers.end());
-}
-
-void LoopBodyInfo::incorporate(BasicBlock &BB) {
- for (BasicBlock::iterator I = BB.begin(), E = --BB.end(); I != E; ++I)
- if (CallInst *CI = dyn_cast<CallInst>(&*I))
- Calls.push_back(CI);
- else if (StoreInst *SI = dyn_cast<StoreInst>(&*I))
- StoredPointers.insert(SI->getOperand(1));
- else if (LoadInst *LI = dyn_cast<LoadInst>(&*I))
- LoadedPointers.insert(LI->getOperand(0));
-
- if (InvokeInst *II = dyn_cast<InvokeInst>(BB.getTerminator()))
- Invokes.push_back(II);
-}
-
-
-// calculatePointerInfo - Calculate information about the specified pointer.
-LoopBodyInfo::PointerClass LoopBodyInfo::calculatePointerInfo(Value *V,
- AliasAnalysis &AA) const {
- for (unsigned i = 0, e = Calls.size(); i != e; ++i)
- if (AA.getModRefInfo(Calls[i], V, ~0))
- return PointerMayStore;
-
- for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
- if (AA.getModRefInfo(Invokes[i], V, ~0))
- return PointerMayStore;
-
- PointerClass Result = PointerNoStore;
- for (std::set<Value*>::const_iterator I = StoredPointers.begin(),
- E = StoredPointers.end(); I != E; ++I)
- if (AA.alias(V, ~0, *I, ~0))
- if (V == *I)
- Result = PointerMustStore; // If this is the only alias, return must
- else
- return PointerMayStore; // We have to return may
- return Result;
-}
-
-namespace {
struct LICM : public FunctionPass, public InstVisitor<LICM> {
virtual bool runOnFunction(Function &F);
///
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.setPreservesCFG();
- AU.addRequiredID(LoopPreheadersID);
+ AU.addRequiredID(LoopSimplifyID);
AU.addRequired<LoopInfo>();
AU.addRequired<DominatorTree>();
- AU.addRequired<DominanceFrontier>();
+ AU.addRequired<DominanceFrontier>(); // For scalar promotion (mem2reg)
AU.addRequired<AliasAnalysis>();
}
private:
LoopInfo *LI; // Current LoopInfo
AliasAnalysis *AA; // Current AliasAnalysis information
+ DominanceFrontier *DF; // Current Dominance Frontier
bool Changed; // Set to true when we change anything.
BasicBlock *Preheader; // The preheader block of the current loop...
Loop *CurLoop; // The current loop we are working on...
- LoopBodyInfo *CurLBI; // Information about the current loop...
+ AliasSetTracker *CurAST; // AliasSet information for the current loop...
+ DominatorTree *DT; // Dominator Tree for the current Loop...
/// visitLoop - Hoist expressions out of the specified loop...
///
- void visitLoop(Loop *L, LoopBodyInfo &LBI);
+ void visitLoop(Loop *L, AliasSetTracker &AST);
/// HoistRegion - Walk the specified region of the CFG (defined by all
/// blocks dominated by the specified block, and that are in the current
/// loop) in depth first order w.r.t the DominatorTree. This allows us to
- /// visit defintions before uses, allowing us to hoist a loop body in one
+ /// visit definitions before uses, allowing us to hoist a loop body in one
/// pass without iteration.
///
void HoistRegion(DominatorTree::Node *N);
///
void hoist(Instruction &I);
+ /// SafeToHoist - Only hoist an instruction if it is not a trapping instruction
+ /// or if it is a trapping instruction and is guaranteed to execute
+ ///
+ bool SafeToHoist(Instruction &I);
+
/// pointerInvalidatedByLoop - Return true if the body of this loop may
/// store into the memory location pointed to by V.
///
bool pointerInvalidatedByLoop(Value *V) {
- // Check to see if any of the basic blocks in CurLoop invalidate V.
- return CurLBI->getPointerInfo(V, *AA) != LoopBodyInfo::PointerNoStore;
+ // Check to see if any of the basic blocks in CurLoop invalidate *V.
+ return CurAST->getAliasSetForPointer(V, 0).isMod();
}
/// isLoopInvariant - Return true if the specified value is loop invariant
void PromoteValuesInLoop();
/// findPromotableValuesInLoop - Check the current loop for stores to
- /// definate pointers, which are not loaded and stored through may aliases.
+ /// definite pointers, which are not loaded and stored through may aliases.
/// If these are found, create an alloca for the value, add it to the
/// PromotedValues list, and keep track of the mapping from value to
/// alloca...
///
friend class InstVisitor<LICM>;
void visitBinaryOperator(Instruction &I) {
- if (isLoopInvariant(I.getOperand(0)) && isLoopInvariant(I.getOperand(1)))
+ if (isLoopInvariant(I.getOperand(0)) && isLoopInvariant(I.getOperand(1)) && SafeToHoist(I))
hoist(I);
}
void visitCastInst(CastInst &CI) {
Instruction &I = (Instruction&)CI;
- if (isLoopInvariant(I.getOperand(0))) hoist(I);
+ if (isLoopInvariant(I.getOperand(0)) && SafeToHoist(CI)) hoist(I);
}
void visitShiftInst(ShiftInst &I) { visitBinaryOperator((Instruction&)I); }
Instruction &I = (Instruction&)GEPI;
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
if (!isLoopInvariant(I.getOperand(i))) return;
- hoist(I);
+ if(SafeToHoist(GEPI))
+ hoist(I);
}
};
// Get our Loop and Alias Analysis information...
LI = &getAnalysis<LoopInfo>();
AA = &getAnalysis<AliasAnalysis>();
+ DF = &getAnalysis<DominanceFrontier>();
+ DT = &getAnalysis<DominatorTree>();
// Hoist expressions out of all of the top-level loops.
const std::vector<Loop*> &TopLevelLoops = LI->getTopLevelLoops();
for (std::vector<Loop*>::const_iterator I = TopLevelLoops.begin(),
E = TopLevelLoops.end(); I != E; ++I) {
- LoopBodyInfo LBI;
- LICM::visitLoop(*I, LBI);
+ AliasSetTracker AST(*AA);
+ LICM::visitLoop(*I, AST);
}
return Changed;
}
/// visitLoop - Hoist expressions out of the specified loop...
///
-void LICM::visitLoop(Loop *L, LoopBodyInfo &LBI) {
+void LICM::visitLoop(Loop *L, AliasSetTracker &AST) {
// Recurse through all subloops before we process this loop...
for (std::vector<Loop*>::const_iterator I = L->getSubLoops().begin(),
E = L->getSubLoops().end(); I != E; ++I) {
- LoopBodyInfo SubLBI;
- LICM::visitLoop(*I, SubLBI);
+ AliasSetTracker SubAST(*AA);
+ LICM::visitLoop(*I, SubAST);
// Incorporate information about the subloops into this loop...
- LBI.incorporate(SubLBI);
+ AST.add(SubAST);
}
CurLoop = L;
- CurLBI = &LBI;
+ CurAST = &AST;
// Get the preheader block to move instructions into...
Preheader = L->getLoopPreheader();
assert(Preheader&&"Preheader insertion pass guarantees we have a preheader!");
// Loop over the body of this loop, looking for calls, invokes, and stores.
- // Because subloops have already been incorporated into LBI, we skip blocks in
+ // Because subloops have already been incorporated into AST, we skip blocks in
// subloops.
//
const std::vector<BasicBlock*> &LoopBBs = L->getBlocks();
for (std::vector<BasicBlock*>::const_iterator I = LoopBBs.begin(),
E = LoopBBs.end(); I != E; ++I)
if (LI->getLoopFor(*I) == L) // Ignore blocks in subloops...
- LBI.incorporate(**I); // Incorporate the specified basic block
+ AST.add(**I); // Incorporate the specified basic block
// We want to visit all of the instructions in this loop... that are not parts
// of our subloops (they have already had their invariants hoisted out of
// that we are guaranteed to see definitions before we see uses. This allows
// us to perform the LICM transformation in one pass, without iteration.
//
- HoistRegion(getAnalysis<DominatorTree>()[L->getHeader()]);
+ HoistRegion(DT->getNode(L->getHeader()));
// Now that all loop invariants have been removed from the loop, promote any
// memory references to scalars that we can...
/// HoistRegion - Walk the specified region of the CFG (defined by all blocks
/// dominated by the specified block, and that are in the current loop) in depth
-/// first order w.r.t the DominatorTree. This allows us to visit defintions
+/// first order w.r.t the DominatorTree. This allows us to visit definitions
/// before uses, allowing us to hoist a loop body in one pass without iteration.
///
void LICM::HoistRegion(DominatorTree::Node *N) {
assert(N != 0 && "Null dominator tree node?");
// If this subregion is not in the top level loop at all, exit.
- if (!CurLoop->contains(N->getNode())) return;
+ if (!CurLoop->contains(N->getBlock())) return;
// Only need to hoist the contents of this block if it is not part of a
// subloop (which would already have been hoisted)
- if (!inSubLoop(N->getNode()))
- visit(*N->getNode());
+ if (!inSubLoop(N->getBlock()))
+ visit(*N->getBlock());
const std::vector<DominatorTree::Node*> &Children = N->getChildren();
for (unsigned i = 0, e = Children.size(); i != e; ++i)
Changed = true;
}
+/// SafeToHoist - Only hoist an instruction if it is not a trapping instruction
+/// or if it is a trapping instruction and is guaranteed to execute
+///
+bool LICM::SafeToHoist(Instruction &Inst) {
+
+ //If it is a trapping instruction, then check if its guaranteed to execute.
+ if(Inst.isTrapping()) {
+
+ //Get the instruction's basic block.
+ BasicBlock *InstBB = Inst.getParent();
+
+ //Get the Dominator Tree Node for the instruction's basic block/
+ DominatorTree::Node *InstDTNode = DT->getNode(InstBB);
+
+ //Get the exit blocks for the current loop.
+ const std::vector<BasicBlock* > &ExitBlocks = CurLoop->getExitBlocks();
+
+ //For each exit block, get the DT node and walk up the DT until
+ //the instruction's basic block is found or we exit the loop.
+ for(unsigned i=0; i < ExitBlocks.size(); ++i) {
+ DominatorTree::Node *IDom = DT->getNode(ExitBlocks[i]);
+
+ while(IDom != InstDTNode) {
+
+ //Get next Immediate Dominator.
+ IDom = IDom->getIDom();
+
+ //See if we exited the loop.
+ if(!CurLoop->contains(IDom->getBlock()))
+ return false;
+ }
+ }
+ }
+
+ return true;
+}
+
void LICM::visitLoadInst(LoadInst &LI) {
- if (isLoopInvariant(LI.getOperand(0)) &&
- !pointerInvalidatedByLoop(LI.getOperand(0))) {
+ if (isLoopInvariant(LI.getOperand(0)) && !LI.isVolatile() &&
+ !pointerInvalidatedByLoop(LI.getOperand(0)) && SafeToHoist(LI)) {
hoist(LI);
++NumHoistedLoads;
}
///
void LICM::PromoteValuesInLoop() {
// PromotedValues - List of values that are promoted out of the loop. Each
- // value has an alloca instruction for it, and a cannonical version of the
+ // value has an alloca instruction for it, and a canonical version of the
// pointer.
std::vector<std::pair<AllocaInst*, Value*> > PromotedValues;
std::map<Value*, AllocaInst*> ValueToAllocaMap; // Map of ptr to alloca
// Rewrite all loads and stores in the block of the pointer...
for (BasicBlock::iterator II = (*I)->begin(), E = (*I)->end();
II != E; ++II) {
- if (LoadInst *L = dyn_cast<LoadInst>(&*II)) {
+ if (LoadInst *L = dyn_cast<LoadInst>(II)) {
std::map<Value*, AllocaInst*>::iterator
I = ValueToAllocaMap.find(L->getOperand(0));
if (I != ValueToAllocaMap.end())
L->setOperand(0, I->second); // Rewrite load instruction...
- } else if (StoreInst *S = dyn_cast<StoreInst>(&*II)) {
+ } else if (StoreInst *S = dyn_cast<StoreInst>(II)) {
std::map<Value*, AllocaInst*>::iterator
I = ValueToAllocaMap.find(S->getOperand(1));
if (I != ValueToAllocaMap.end())
PromotedAllocas.reserve(PromotedValues.size());
for (unsigned i = 0, e = PromotedValues.size(); i != e; ++i)
PromotedAllocas.push_back(PromotedValues[i].first);
- PromoteMemToReg(PromotedAllocas, getAnalysis<DominanceFrontier>());
+ PromoteMemToReg(PromotedAllocas, *DT, *DF, AA->getTargetData());
}
-/// findPromotableValuesInLoop - Check the current loop for stores to definate
+/// findPromotableValuesInLoop - Check the current loop for stores to definite
/// pointers, which are not loaded and stored through may aliases. If these are
/// found, create an alloca for the value, add it to the PromotedValues list,
/// and keep track of the mapping from value to alloca...
std::map<Value*, AllocaInst*> &ValueToAllocaMap) {
Instruction *FnStart = CurLoop->getHeader()->getParent()->begin()->begin();
- for (std::set<Value*>::iterator I = CurLBI->StoredPointers.begin(),
- E = CurLBI->StoredPointers.end(); I != E; ++I) {
- Value *V = *I;
- if (isLoopInvariant(V) &&
- CurLBI->getPointerInfo(V, *AA) == LoopBodyInfo::PointerMustStore) {
-
- // Don't add a new entry for this stored pointer if it aliases something
- // we have already processed.
- std::map<Value*, AllocaInst*>::iterator V2AMI =
- ValueToAllocaMap.lower_bound(V);
- if (V2AMI == ValueToAllocaMap.end() || V2AMI->first != V) {
- // Check to make sure that any loads in the loop are either NO or MUST
- // aliases. We cannot rewrite loads that _might_ come from this memory
- // location.
-
- bool PointerOk = true;
- for (std::set<Value*>::const_iterator I =CurLBI->LoadedPointers.begin(),
- E = CurLBI->LoadedPointers.end(); I != E; ++I)
- if (AA->alias(V, ~0, *I, ~0) == AliasAnalysis::MayAlias) {
- PointerOk = false;
- break;
- }
-
- if (PointerOk) {
- const Type *Ty = cast<PointerType>(V->getType())->getElementType();
- AllocaInst *AI = new AllocaInst(Ty, 0, V->getName()+".tmp", FnStart);
- PromotedValues.push_back(std::make_pair(AI, V));
- ValueToAllocaMap.insert(V2AMI, std::make_pair(V, AI));
-
- DEBUG(std::cerr << "LICM: Promoting value: " << *V << "\n");
-
- // Loop over all of the loads and stores that alias this pointer,
- // adding them to the Value2AllocaMap as well...
- for (std::set<Value*>::const_iterator
- I = CurLBI->LoadedPointers.begin(),
- E = CurLBI->LoadedPointers.end(); I != E; ++I)
- if (AA->alias(V, ~0, *I, ~0) == AliasAnalysis::MustAlias)
- ValueToAllocaMap[*I] = AI;
-
- for (std::set<Value*>::const_iterator
- I = CurLBI->StoredPointers.begin(),
- E = CurLBI->StoredPointers.end(); I != E; ++I)
- if (AA->alias(V, ~0, *I, ~0) == AliasAnalysis::MustAlias)
- ValueToAllocaMap[*I] = AI;
+ // Loop over all of the alias sets in the tracker object...
+ for (AliasSetTracker::iterator I = CurAST->begin(), E = CurAST->end();
+ I != E; ++I) {
+ AliasSet &AS = *I;
+ // We can promote this alias set if it has a store, if it is a "Must" alias
+ // set, and if the pointer is loop invariant.
+ if (!AS.isForwardingAliasSet() && AS.isMod() && AS.isMustAlias() &&
+ isLoopInvariant(AS.begin()->first)) {
+ assert(AS.begin() != AS.end() &&
+ "Must alias set should have at least one pointer element in it!");
+ Value *V = AS.begin()->first;
+
+ // Check that all of the pointers in the alias set have the same type. We
+ // cannot (yet) promote a memory location that is loaded and stored in
+ // different sizes.
+ bool PointerOk = true;
+ for (AliasSet::iterator I = AS.begin(), E = AS.end(); I != E; ++I)
+ if (V->getType() != I->first->getType()) {
+ PointerOk = false;
+ break;
}
+
+ if (PointerOk) {
+ const Type *Ty = cast<PointerType>(V->getType())->getElementType();
+ AllocaInst *AI = new AllocaInst(Ty, 0, V->getName()+".tmp", FnStart);
+ PromotedValues.push_back(std::make_pair(AI, V));
+
+ for (AliasSet::iterator I = AS.begin(), E = AS.end(); I != E; ++I)
+ ValueToAllocaMap.insert(std::make_pair(I->first, AI));
+
+ DEBUG(std::cerr << "LICM: Promoting value: " << *V << "\n");
}
}
}
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