SLPVectorization: Add a basic support for cross-basic block slp vectorization.

We collect gather sequences when we vectorize basic blocks. Gather sequences are excellent
hints for vectorization of other basic blocks.

llvm-svn: 184444

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Vectorize/VecUtils.cpp b/llvm/lib/Transforms/Vectorize/VecUtils.cpp
index e79f08a56dd..88c457d1176 100644
--- a/llvm/lib/Transforms/Vectorize/VecUtils.cpp
+++ b/llvm/lib/Transforms/Vectorize/VecUtils.cpp
@@ -731,9 +731,13 @@ Value *BoUpSLP::Scalarize(ArrayRef<Value *> VL, VectorType *Ty) {
     // Remember that this instruction is used as part of a 'gather' sequence.
     // The caller of the bottom-up slp vectorizer can try to hoist the sequence
     // if the users are outside of the basic block.
-    GatherInstructions.push_back(Vec);
+    if (InsertElementInst *IEI = dyn_cast<InsertElementInst>(Vec))
+      GatherInstructions.push_back(IEI);
   }
 
+  // Mark the end of the gather sequence.
+  GatherInstructions.push_back(0);
+
   for (unsigned i = 0; i < Ty->getNumElements(); ++i)
     VectorizedValues[VL[i]] = Vec;