[llvm-commits] CVS: llvm/lib/Transforms/Scalar/LICM.cpp
Chris Lattner
lattner at cs.uiuc.edu
Mon Mar 3 17:33:00 PST 2003
Changes in directory llvm/lib/Transforms/Scalar:
LICM.cpp updated: 1.25 -> 1.26
---
Log message:
Convert LICM over to use AliasSetTracker. Besides being nicer, this automatically
allows LICM to use access sizes to help alias analysis be more precise.
---
Diffs of the changes:
Index: llvm/lib/Transforms/Scalar/LICM.cpp
diff -u llvm/lib/Transforms/Scalar/LICM.cpp:1.25 llvm/lib/Transforms/Scalar/LICM.cpp:1.26
--- llvm/lib/Transforms/Scalar/LICM.cpp:1.25 Mon Mar 3 11:25:16 2003
+++ llvm/lib/Transforms/Scalar/LICM.cpp Mon Mar 3 17:32:45 2003
@@ -24,6 +24,7 @@
#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"
@@ -43,106 +44,6 @@
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);
@@ -154,7 +55,7 @@
AU.addRequiredID(LoopPreheadersID);
AU.addRequired<LoopInfo>();
AU.addRequired<DominatorTree>();
- AU.addRequired<DominanceFrontier>();
+ AU.addRequired<DominanceFrontier>(); // For scalar promotion (mem2reg)
AU.addRequired<AliasAnalysis>();
}
@@ -164,11 +65,11 @@
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...
/// 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
@@ -198,8 +99,8 @@
/// 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
@@ -269,8 +170,8 @@
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;
}
@@ -278,32 +179,32 @@
/// 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
@@ -472,57 +373,37 @@
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(); PointerOk && I != E; ++I)
- switch (AA->alias(V, ~0, *I, ~0)) {
- case AliasAnalysis::MustAlias:
- if (V->getType() != (*I)->getType())
- PointerOk = false;
- break;
- case AliasAnalysis::MayAlias:
- PointerOk = false;
- case AliasAnalysis::NoAlias:
- 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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