diff options
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineInternal.h | 2 | ||||
| -rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp | 77 |
2 files changed, 28 insertions, 51 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h index 431856c9e00..6c9a3facf51 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h +++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h @@ -920,7 +920,7 @@ private: bool isSigned, bool Inside); Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI); Instruction *MatchBSwap(BinaryOperator &I); - bool SimplifyStoreAtEndOfBlock(StoreInst &SI); + bool mergeStoreIntoSuccessor(StoreInst &SI); Instruction *SimplifyAnyMemTransfer(AnyMemTransferInst *MI); Instruction *SimplifyAnyMemSet(AnyMemSetInst *MI); diff --git a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp index 1ff7037c8d2..670168bf537 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp @@ -1498,64 +1498,45 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) { if (isa<UndefValue>(Val)) return eraseInstFromFunction(SI); - // If this store is the last instruction in the basic block (possibly - // excepting debug info instructions), and if the block ends with an - // unconditional branch, try to move it to the successor block. + // If this store is the second-to-last instruction in the basic block + // (excluding debug info and bitcasts of pointers) and if the block ends with + // an unconditional branch, try to move the store to the successor block. BBI = SI.getIterator(); do { ++BBI; } while (isa<DbgInfoIntrinsic>(BBI) || (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())); + if (BranchInst *BI = dyn_cast<BranchInst>(BBI)) if (BI->isUnconditional()) - if (SimplifyStoreAtEndOfBlock(SI)) - return nullptr; // xform done! + mergeStoreIntoSuccessor(SI); return nullptr; } -/// SimplifyStoreAtEndOfBlock - Turn things like: +/// Try to transform: /// if () { *P = v1; } else { *P = v2 } -/// into a phi node with a store in the successor. -/// -/// Simplify things like: +/// or: /// *P = v1; if () { *P = v2; } /// into a phi node with a store in the successor. -/// -bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { +bool InstCombiner::mergeStoreIntoSuccessor(StoreInst &SI) { assert(SI.isUnordered() && - "this code has not been auditted for volatile or ordered store case"); + "This code has not been audited for volatile or ordered store case."); + // Check if the successor block has exactly 2 incoming edges. BasicBlock *StoreBB = SI.getParent(); - - // Check to see if the successor block has exactly two incoming edges. If - // so, see if the other predecessor contains a store to the same location. - // if so, insert a PHI node (if needed) and move the stores down. BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0); - - // Determine whether Dest has exactly two predecessors and, if so, compute - // the other predecessor. - pred_iterator PI = pred_begin(DestBB); - BasicBlock *P = *PI; - BasicBlock *OtherBB = nullptr; - - if (P != StoreBB) - OtherBB = P; - - if (++PI == pred_end(DestBB)) + if (pred_size(DestBB) != 2) return false; - P = *PI; - if (P != StoreBB) { - if (OtherBB) - return false; - OtherBB = P; - } - if (++PI != pred_end(DestBB)) - return false; + // Capture the other block (the block that doesn't contain our store). + pred_iterator PredIter = pred_begin(DestBB); + if (*PredIter == StoreBB) + ++PredIter; + BasicBlock *OtherBB = *PredIter; - // Bail out if all the relevant blocks aren't distinct (this can happen, - // for example, if SI is in an infinite loop) + // Bail out if all of the relevant blocks aren't distinct. This can happen, + // for example, if SI is in an infinite loop. if (StoreBB == DestBB || OtherBB == DestBB) return false; @@ -1566,7 +1547,7 @@ bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { return false; // If the other block ends in an unconditional branch, check for the 'if then - // else' case. there is an instruction before the branch. + // else' case. There is an instruction before the branch. StoreInst *OtherStore = nullptr; if (OtherBr->isUnconditional()) { --BBI; @@ -1591,7 +1572,7 @@ bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { return false; // Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an - // if/then triangle. See if there is a store to the same ptr as SI that + // if/then triangle. See if there is a store to the same ptr as SI that // lives in OtherBB. for (;; --BBI) { // Check to see if we find the matching store. @@ -1602,15 +1583,14 @@ bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { break; } // If we find something that may be using or overwriting the stored - // value, or if we run out of instructions, we can't do the xform. + // value, or if we run out of instructions, we can't do the transform. if (BBI->mayReadFromMemory() || BBI->mayThrow() || BBI->mayWriteToMemory() || BBI == OtherBB->begin()) return false; } - // In order to eliminate the store in OtherBr, we have to - // make sure nothing reads or overwrites the stored value in - // StoreBB. + // In order to eliminate the store in OtherBr, we have to make sure nothing + // reads or overwrites the stored value in StoreBB. for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) { // FIXME: This should really be AA driven. if (I->mayReadFromMemory() || I->mayThrow() || I->mayWriteToMemory()) @@ -1627,16 +1607,13 @@ bool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { MergedVal = InsertNewInstBefore(PN, DestBB->front()); } - // Advance to a place where it is safe to insert the new store and - // insert it. + // Advance to a place where it is safe to insert the new store and insert it. BBI = DestBB->getFirstInsertionPt(); StoreInst *NewSI = new StoreInst(MergedVal, SI.getOperand(1), - SI.isVolatile(), - SI.getAlignment(), - SI.getOrdering(), - SI.getSyncScopeID()); + SI.isVolatile(), SI.getAlignment(), + SI.getOrdering(), SI.getSyncScopeID()); InsertNewInstBefore(NewSI, *BBI); - // The debug locations of the original instructions might differ; merge them. + // The debug locations of the original instructions might differ. Merge them. NewSI->applyMergedLocation(SI.getDebugLoc(), OtherStore->getDebugLoc()); // If the two stores had AA tags, merge them. |
