Pass *llvm::createLICMPass() { return new LICM(); }
/// Hoist expressions out of the specified loop. Note, alias info for inner
-/// loop is not preserved so it is not a good idea to run LICM multiple
+/// loop is not preserved so it is not a good idea to run LICM multiple
/// times on one loop.
///
bool LICM::runOnLoop(Loop *L, LPPassManager &LPM) {
// What if InnerLoop was modified by other passes ?
CurAST->add(*InnerAST);
-
+
// Once we've incorporated the inner loop's AST into ours, we don't need the
// subloop's anymore.
delete InnerAST;
LoopToAliasSetMap.erase(InnerL);
}
-
+
CurLoop = L;
// Get the preheader block to move instructions into...
I != E; ++I)
PromoteAliasSet(*I);
}
-
+
// Clear out loops state information for the next iteration
CurLoop = 0;
Preheader = 0;
for (BasicBlock::iterator II = BB->end(); II != BB->begin(); ) {
Instruction &I = *--II;
-
+
// If the instruction is dead, we would try to sink it because it isn't used
// in the loop, instead, just delete it.
if (isInstructionTriviallyDead(&I)) {
I.eraseFromParent();
continue;
}
-
+
// Try hoisting the instruction out to the preheader. We can only do this
// if all of the operands of the instruction are loop invariant and if it
// is safe to hoist the instruction.
// in the same alias set as something that ends up being modified.
if (AA->pointsToConstantMemory(LI->getOperand(0)))
return true;
-
+
// Don't hoist loads which have may-aliased stores in loop.
uint64_t Size = 0;
if (LI->getType()->isSized())
}
return;
}
-
+
if (ExitBlocks.empty()) {
// The instruction is actually dead if there ARE NO exit blocks.
CurAST->deleteValue(&I);
I.eraseFromParent();
return;
}
-
+
// Otherwise, if we have multiple exits, use the SSAUpdater to do all of the
// hard work of inserting PHI nodes as necessary.
SmallVector<PHINode*, 8> NewPHIs;
SSAUpdater SSA(&NewPHIs);
-
+
if (!I.use_empty())
SSA.Initialize(I.getType(), I.getName());
-
+
// Insert a copy of the instruction in each exit block of the loop that is
// dominated by the instruction. Each exit block is known to only be in the
// ExitBlocks list once.
BasicBlock *InstOrigBB = I.getParent();
unsigned NumInserted = 0;
-
+
for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
BasicBlock *ExitBlock = ExitBlocks[i];
-
+
if (!DT->dominates(InstOrigBB, ExitBlock))
continue;
-
+
// Insert the code after the last PHI node.
BasicBlock::iterator InsertPt = ExitBlock->getFirstNonPHI();
-
+
// If this is the first exit block processed, just move the original
// instruction, otherwise clone the original instruction and insert
// the copy.
New->setName(I.getName()+".le");
ExitBlock->getInstList().insert(InsertPt, New);
}
-
+
// Now that we have inserted the instruction, inform SSAUpdater.
if (!I.use_empty())
SSA.AddAvailableValue(ExitBlock, New);
}
-
+
// If the instruction doesn't dominate any exit blocks, it must be dead.
if (NumInserted == 0) {
CurAST->deleteValue(&I);
I.eraseFromParent();
return;
}
-
+
// Next, rewrite uses of the instruction, inserting PHI nodes as needed.
for (Value::use_iterator UI = I.use_begin(), UE = I.use_end(); UI != UE; ) {
// Grab the use before incrementing the iterator.
++UI;
SSA.RewriteUseAfterInsertions(U);
}
-
+
// Update CurAST for NewPHIs if I had pointer type.
if (I.getType()->isPointerTy())
for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
CurAST->copyValue(&I, NewPHIs[i]);
-
+
// Finally, remove the instruction from CurAST. It is no longer in the loop.
CurAST->deleteValue(&I);
}
: LoadAndStorePromoter(Insts, S, 0, 0), SomePtr(SP),
PointerMustAliases(PMA), LoopExitBlocks(LEB), AST(ast), DL(dl),
Alignment(alignment) {}
-
+
virtual bool isInstInList(Instruction *I,
const SmallVectorImpl<Instruction*> &) const {
Value *Ptr;
Ptr = cast<StoreInst>(I)->getPointerOperand();
return PointerMustAliases.count(Ptr);
}
-
+
virtual void doExtraRewritesBeforeFinalDeletion() const {
// Insert stores after in the loop exit blocks. Each exit block gets a
// store of the live-out values that feed them. Since we've already told
if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() ||
AS.isVolatile() || !CurLoop->isLoopInvariant(AS.begin()->getValue()))
return;
-
+
assert(!AS.empty() &&
"Must alias set should have at least one pointer element in it!");
Value *SomePtr = AS.begin()->getValue();
// tmp = *P; for () { if (c) tmp +=1; } *P = tmp;
//
// is not safe, because *P may only be valid to access if 'c' is true.
- //
+ //
// It is safe to promote P if all uses are direct load/stores and if at
// least one is guaranteed to be executed.
bool GuaranteedToExecute = false;
for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
Value *ASIV = ASI->getValue();
PointerMustAliases.insert(ASIV);
-
+
// 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.
if (SomePtr->getType() != ASIV->getType())
return;
-
+
for (Value::use_iterator UI = ASIV->use_begin(), UE = ASIV->use_end();
UI != UE; ++UI) {
// Ignore instructions that are outside the loop.
Instruction *Use = dyn_cast<Instruction>(*UI);
if (!Use || !CurLoop->contains(Use))
continue;
-
+
// If there is an non-load/store instruction in the loop, we can't promote
// it.
unsigned InstAlignment;
if (!GuaranteedToExecute)
GuaranteedToExecute = isSafeToExecuteUnconditionally(*Use);
-
+
LoopUses.push_back(Use);
}
}
// If there isn't a guaranteed-to-execute instruction, we can't promote.
if (!GuaranteedToExecute)
return;
-
+
// Otherwise, this is safe to promote, lets do it!
- DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n');
+ DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n');
Changed = true;
++NumPromoted;
SmallVector<BasicBlock*, 8> ExitBlocks;
CurLoop->getUniqueExitBlocks(ExitBlocks);
-
+
// We use the SSAUpdater interface to insert phi nodes as required.
SmallVector<PHINode*, 16> NewPHIs;
SSAUpdater SSA(&NewPHIs);
LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks,
*CurAST, DL, Alignment);
-
+
// Set up the preheader to have a definition of the value. It is the live-out
// value from the preheader that uses in the loop will use.
LoadInst *PreheaderLoad =
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