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Sink store based on alias analysis 

- by Ella Bolshinsky
The alias analysis is used define whether the given instruction
is a barrier for store sinking. For 2 identical stores, following
instructions are checked in the both basic blocks, to determine
whether they are sinking barriers.

http://reviews.llvm.org/D6420

llvm-svn: 224247
This commit is contained in:
Elena Demikhovsky 2014-12-15 14:09:53 +00:00
parent 47c97157ef
commit a5599bfd72
4 changed files with 62 additions and 62 deletions
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25
llvm/include/llvm/Analysis/AliasAnalysis.h
View File

@ -502,7 +502,7 @@ public:
///
/// canBasicBlockModify - Return true if it is possible for execution of the
/// specified basic block to modify the value pointed to by Ptr.
/// specified basic block to modify the location Loc.
bool canBasicBlockModify(const BasicBlock &BB, const Location &Loc);
/// canBasicBlockModify - A convenience wrapper.
@ -510,17 +510,20 @@ public:
return canBasicBlockModify(BB, Location(P, Size));
}
/// canInstructionRangeModify - Return true if it is possible for the
/// execution of the specified instructions to modify the value pointed to by
/// Ptr. The instructions to consider are all of the instructions in the
/// range of [I1,I2] INCLUSIVE. I1 and I2 must be in the same basic block.
bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2,
const Location &Loc);
/// canInstructionRangeModRef - Return true if it is possible for the
/// execution of the specified instructions to mod\ref (according to the
/// mode) the location Loc. The instructions to consider are all
/// of the instructions in the range of [I1,I2] INCLUSIVE.
/// I1 and I2 must be in the same basic block.
bool canInstructionRangeModRef(const Instruction &I1,
const Instruction &I2, const Location &Loc,
const ModRefResult Mode);
/// canInstructionRangeModify - A convenience wrapper.
bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2,
const Value *Ptr, uint64_t Size) {
return canInstructionRangeModify(I1, I2, Location(Ptr, Size));
/// canInstructionRangeModRef - A convenience wrapper.
bool canInstructionRangeModRef(const Instruction &I1,
const Instruction &I2, const Value *Ptr,
uint64_t Size, const ModRefResult Mode) {
return canInstructionRangeModRef(I1, I2, Location(Ptr, Size), Mode);
}
//===--------------------------------------------------------------------===//

21
llvm/lib/Analysis/AliasAnalysis.cpp
View File

@ -483,21 +483,22 @@ uint64_t AliasAnalysis::getTypeStoreSize(Type *Ty) {
}
/// canBasicBlockModify - Return true if it is possible for execution of the
/// specified basic block to modify the value pointed to by Ptr.
/// specified basic block to modify the location Loc.
///
bool AliasAnalysis::canBasicBlockModify(const BasicBlock &BB,
const Location &Loc) {
return canInstructionRangeModify(BB.front(), BB.back(), Loc);
return canInstructionRangeModRef(BB.front(), BB.back(), Loc, Mod);
}
/// canInstructionRangeModify - Return true if it is possible for the execution
/// of the specified instructions to modify the value pointed to by Ptr. The
/// instructions to consider are all of the instructions in the range of [I1,I2]
/// INCLUSIVE. I1 and I2 must be in the same basic block.
///
bool AliasAnalysis::canInstructionRangeModify(const Instruction &I1,
/// canInstructionRangeModRef - Return true if it is possible for the
/// execution of the specified instructions to mod\ref (according to the
/// mode) the location Loc. The instructions to consider are all
/// of the instructions in the range of [I1,I2] INCLUSIVE.
/// I1 and I2 must be in the same basic block.
bool AliasAnalysis::canInstructionRangeModRef(const Instruction &I1,
const Instruction &I2,
const Location &Loc) {
const Location &Loc,
const ModRefResult Mode) {
assert(I1.getParent() == I2.getParent() &&
"Instructions not in same basic block!");
BasicBlock::const_iterator I = &I1;
@ -505,7 +506,7 @@ bool AliasAnalysis::canInstructionRangeModify(const Instruction &I1,
++E; // Convert from inclusive to exclusive range.
for (; I != E; ++I) // Check every instruction in range
if (getModRefInfo(I, Loc) & Mod)
if (getModRefInfo(I, Loc) & Mode)
return true;
return false;
}

3
llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
View File

@ -554,7 +554,8 @@ bool ArgPromotion::isSafeToPromoteArgument(Argument *Arg,
BasicBlock *BB = Load->getParent();
AliasAnalysis::Location Loc = AA.getLocation(Load);
if (AA.canInstructionRangeModify(BB->front(), *Load, Loc))
if (AA.canInstructionRangeModRef(BB->front(), *Load, Loc,
AliasAnalysis::Mod))
return false; // Pointer is invalidated!
// Now check every path from the entry block to the load for transparency.

75
llvm/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
View File

@ -143,7 +143,9 @@ private:
// Routines for sinking stores
StoreInst *canSinkFromBlock(BasicBlock *BB, StoreInst *SI);
PHINode *getPHIOperand(BasicBlock *BB, StoreInst *S0, StoreInst *S1);
bool isStoreSinkBarrier(Instruction *Inst);
bool isStoreSinkBarrierInRange(const Instruction& Start,
const Instruction& End,
AliasAnalysis::Location Loc);
bool sinkStore(BasicBlock *BB, StoreInst *SinkCand, StoreInst *ElseInst);
bool mergeStores(BasicBlock *BB);
// The mergeLoad/Store algorithms could have Size0 * Size1 complexity,
@ -239,7 +241,7 @@ bool MergedLoadStoreMotion::isLoadHoistBarrierInRange(const Instruction& Start,
const Instruction& End,
LoadInst* LI) {
AliasAnalysis::Location Loc = AA->getLocation(LI);
return AA->canInstructionRangeModify(Start, End, Loc);
return AA->canInstructionRangeModRef(Start, End, Loc, AliasAnalysis::Mod);
}
///
@ -389,26 +391,19 @@ bool MergedLoadStoreMotion::mergeLoads(BasicBlock *BB) {
}
///
/// \brief True when instruction is sink barrier for a store
///
bool MergedLoadStoreMotion::isStoreSinkBarrier(Instruction *Inst) {
// FIXME: Conservatively let a load instruction block the store.
// Use alias analysis instead.
if (isa<LoadInst>(Inst))
return true;
if (isa<CallInst>(Inst))
return true;
if (isa<TerminatorInst>(Inst) && !isa<BranchInst>(Inst))
return true;
// Note: mayHaveSideEffects covers all instructions that could
// trigger a change to state. Eg. in-flight stores have to be executed
// before ordered loads or fences, calls could invoke functions that store
// data to memory etc.
if (!isa<StoreInst>(Inst) && Inst->mayHaveSideEffects()) {
return true;
}
DEBUG(dbgs() << "No Sink Barrier\n");
return false;
/// \brief True when instruction is a sink barrier for a store
/// located in Loc
///
/// Whenever an instruction could possibly read or modify the
/// value being stored or protect against the store from
/// happening it is considered a sink barrier.
///
bool MergedLoadStoreMotion::isStoreSinkBarrierInRange(const Instruction& Start,
const Instruction& End,
AliasAnalysis::Location
Loc) {
return AA->canInstructionRangeModRef(Start, End, Loc, AliasAnalysis::Ref);
}
///
@ -416,27 +411,28 @@ bool MergedLoadStoreMotion::isStoreSinkBarrier(Instruction *Inst) {
///
/// \return The store in \p when it is safe to sink. Otherwise return Null.
///
StoreInst *MergedLoadStoreMotion::canSinkFromBlock(BasicBlock *BB,
StoreInst *SI) {
StoreInst *I = 0;
DEBUG(dbgs() << "can Sink? : "; SI->dump(); dbgs() << "\n");
for (BasicBlock::reverse_iterator RBI = BB->rbegin(), RBE = BB->rend();
StoreInst *MergedLoadStoreMotion::canSinkFromBlock(BasicBlock *BB1,
StoreInst *Store0) {
DEBUG(dbgs() << "can Sink? : "; Store0->dump(); dbgs() << "\n");
for (BasicBlock::reverse_iterator RBI = BB1->rbegin(), RBE = BB1->rend();
RBI != RBE; ++RBI) {
Instruction *Inst = &*RBI;
// Only move loads if they are used in the block.
if (isStoreSinkBarrier(Inst))
break;
if (isa<StoreInst>(Inst)) {
AliasAnalysis::Location LocSI = AA->getLocation(SI);
AliasAnalysis::Location LocInst = AA->getLocation((StoreInst *)Inst);
if (AA->isMustAlias(LocSI, LocInst)) {
I = (StoreInst *)Inst;
break;
}
if (!isa<StoreInst>(Inst))
continue;
StoreInst *Store1 = cast<StoreInst>(Inst);
BasicBlock *BB0 = Store0->getParent();
AliasAnalysis::Location Loc0 = AA->getLocation(Store0);
AliasAnalysis::Location Loc1 = AA->getLocation(Store1);
if (AA->isMustAlias(Loc0, Loc1) && Store0->isSameOperationAs(Store1) &&
!isStoreSinkBarrierInRange(*Store1, BB1->back(), Loc1) &&
!isStoreSinkBarrierInRange(*Store0, BB0->back(), Loc0)) {
return Store1;
}
}
return I;
return nullptr;
}
///
@ -548,8 +544,7 @@ bool MergedLoadStoreMotion::mergeStores(BasicBlock *T) {
Instruction *I = &*RBI;
++RBI;
if (isStoreSinkBarrier(I))
break;
// Sink move non-simple (atomic, volatile) stores
if (!isa<StoreInst>(I))
continue;