diff options
Diffstat (limited to 'lib/Transforms/Vectorize/LoopVectorize.cpp')
| -rw-r--r-- | lib/Transforms/Vectorize/LoopVectorize.cpp | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp index ef9c7c9db2..0d11372808 100644 --- a/lib/Transforms/Vectorize/LoopVectorize.cpp +++ b/lib/Transforms/Vectorize/LoopVectorize.cpp @@ -116,6 +116,12 @@ static const unsigned TinyTripCountUnrollThreshold = 128; /// number of pointers. Notice that the check is quadratic! static const unsigned RuntimeMemoryCheckThreshold = 4; +/// We use a metadata with this name to indicate that a scalar loop was +/// vectorized and that we don't need to re-vectorize it if we run into it +/// again. +static const char* +AlreadyVectorizedMDName = "llvm.vectorizer.already_vectorized"; + namespace { // Forward declarations. @@ -1159,6 +1165,11 @@ InnerLoopVectorizer::createEmptyLoop(LoopVectorizationLegality *Legal) { BasicBlock *ExitBlock = OrigLoop->getExitBlock(); assert(ExitBlock && "Must have an exit block"); + // Mark the old scalar loop with metadata that tells us not to vectorize this + // loop again if we run into it. + MDNode *MD = MDNode::get(OldBasicBlock->getContext(), ArrayRef<Value*>()); + OldBasicBlock->getTerminator()->setMetadata(AlreadyVectorizedMDName, MD); + // Some loops have a single integer induction variable, while other loops // don't. One example is c++ iterators that often have multiple pointer // induction variables. In the code below we also support a case where we @@ -2224,6 +2235,13 @@ bool LoopVectorizationLegality::canVectorizeInstrs() { BasicBlock *PreHeader = TheLoop->getLoopPreheader(); BasicBlock *Header = TheLoop->getHeader(); + // If we marked the scalar loop as "already vectorized" then no need + // to vectorize it again. + if (Header->getTerminator()->getMetadata(AlreadyVectorizedMDName)) { + DEBUG(dbgs() << "LV: This loop was vectorized before\n"); + return false; + } + // For each block in the loop. for (Loop::block_iterator bb = TheLoop->block_begin(), be = TheLoop->block_end(); bb != be; ++bb) { |