forked from OSchip/llvm-project
refactor some code, no functionality change.
llvm-svn: 36037
This commit is contained in:
Chris Lattner
parent
0f6ccef96c
commit
14a251b937
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@ -352,6 +352,7 @@ namespace {
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bool isSigned, bool Inside, Instruction &IB);
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Instruction *PromoteCastOfAllocation(CastInst &CI, AllocationInst &AI);
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Instruction *MatchBSwap(BinaryOperator &I);
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bool SimplifyStoreAtEndOfBlock(StoreInst &SI);
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Value *EvaluateInDifferentType(Value *V, const Type *Ty, bool isSigned);
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};
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@ -8818,68 +8819,86 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
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// ends with an unconditional branch, try to move it to the successor block.
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BBI = &SI; ++BBI;
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if (BranchInst *BI = dyn_cast<BranchInst>(BBI))
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if (BI->isUnconditional()) {
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// Check to see if the successor block has exactly two incoming edges. If
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// so, see if the other predecessor contains a store to the same location.
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// if so, insert a PHI node (if needed) and move the stores down.
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BasicBlock *Dest = BI->getSuccessor(0);
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pred_iterator PI = pred_begin(Dest);
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BasicBlock *Other = 0;
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if (*PI != BI->getParent())
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Other = *PI;
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++PI;
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if (PI != pred_end(Dest)) {
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if (*PI != BI->getParent())
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if (Other)
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Other = 0;
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else
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Other = *PI;
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if (++PI != pred_end(Dest))
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Other = 0;
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}
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if (Other) { // If only one other pred...
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BBI = Other->getTerminator();
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// Make sure this other block ends in an unconditional branch and that
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// there is an instruction before the branch.
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if (isa<BranchInst>(BBI) && cast<BranchInst>(BBI)->isUnconditional() &&
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BBI != Other->begin()) {
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--BBI;
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StoreInst *OtherStore = dyn_cast<StoreInst>(BBI);
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// If this instruction is a store to the same location.
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if (OtherStore && OtherStore->getOperand(1) == SI.getOperand(1)) {
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// Okay, we know we can perform this transformation. Insert a PHI
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// node now if we need it.
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Value *MergedVal = OtherStore->getOperand(0);
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if (MergedVal != SI.getOperand(0)) {
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PHINode *PN = new PHINode(MergedVal->getType(), "storemerge");
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PN->reserveOperandSpace(2);
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PN->addIncoming(SI.getOperand(0), SI.getParent());
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PN->addIncoming(OtherStore->getOperand(0), Other);
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MergedVal = InsertNewInstBefore(PN, Dest->front());
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}
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// Advance to a place where it is safe to insert the new store and
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// insert it.
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BBI = Dest->begin();
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while (isa<PHINode>(BBI)) ++BBI;
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InsertNewInstBefore(new StoreInst(MergedVal, SI.getOperand(1),
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OtherStore->isVolatile()), *BBI);
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// Nuke the old stores.
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EraseInstFromFunction(SI);
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EraseInstFromFunction(*OtherStore);
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++NumCombined;
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return 0;
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}
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}
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}
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}
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if (BI->isUnconditional())
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if (SimplifyStoreAtEndOfBlock(SI))
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return 0; // xform done!
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return 0;
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}
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/// SimplifyStoreAtEndOfBlock - Turn things like:
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/// if () { *P = v1; } else { *P = v2 }
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/// into a phi node with a store in the successor.
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///
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bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) {
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BasicBlock *StoreBB = SI.getParent();
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// Check to see if the successor block has exactly two incoming edges. If
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// so, see if the other predecessor contains a store to the same location.
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// if so, insert a PHI node (if needed) and move the stores down.
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BasicBlock *Dest = StoreBB->getTerminator()->getSuccessor(0);
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// Determine whether Dest has exactly two predecessors and, if so, compute
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// the other predecessor.
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pred_iterator PI = pred_begin(Dest);
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BasicBlock *Other = 0;
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if (*PI != StoreBB)
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Other = *PI;
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++PI;
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if (PI == pred_end(Dest))
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return false;
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if (*PI != StoreBB) {
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if (Other)
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return false;
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Other = *PI;
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}
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if (++PI != pred_end(Dest))
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return false;
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BasicBlock::iterator BBI = Other->getTerminator();
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BranchInst *OtherBr = dyn_cast<BranchInst>(BBI);
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// Make sure this other block ends in an unconditional branch and that
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// there is an instruction before the branch.
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if (!OtherBr || !cast<BranchInst>(BBI)->isUnconditional() ||
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BBI == Other->begin())
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return false;
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// See if the last instruction in other block is a store to the same location.
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--BBI;
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StoreInst *OtherStore = dyn_cast<StoreInst>(BBI);
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// If this instruction is a store to the same location.
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if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1))
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return false;
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// Okay, we know we can perform this transformation. Insert a PHI
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// node now if we need it.
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Value *MergedVal = OtherStore->getOperand(0);
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if (MergedVal != SI.getOperand(0)) {
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PHINode *PN = new PHINode(MergedVal->getType(), "storemerge");
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PN->reserveOperandSpace(2);
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PN->addIncoming(SI.getOperand(0), SI.getParent());
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PN->addIncoming(OtherStore->getOperand(0), Other);
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MergedVal = InsertNewInstBefore(PN, Dest->front());
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}
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// Advance to a place where it is safe to insert the new store and
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// insert it.
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BBI = Dest->begin();
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while (isa<PHINode>(BBI)) ++BBI;
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InsertNewInstBefore(new StoreInst(MergedVal, SI.getOperand(1),
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OtherStore->isVolatile()), *BBI);
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// Nuke the old stores.
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EraseInstFromFunction(SI);
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EraseInstFromFunction(*OtherStore);
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++NumCombined;
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return true;
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}
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Instruction *InstCombiner::visitBranchInst(BranchInst &BI) {
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// Change br (not X), label True, label False to: br X, label False, True
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