LoopVectorizer: Don't attempt to vectorize extractelement instructions

The loop vectorizer does not currently understand how to vectorize
extractelement instructions. The existing check, which excluded all
vector-valued instructions, did not catch extractelement instructions because
it checked only the return value. As a result, vectorization would proceed,
producing illegal instructions like this:

  %58 = extractelement <2 x i32> %15, i32 0
  %59 = extractelement i32 %58, i32 0

where the second extractelement is illegal because its first operand is not a vector.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193434 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 3 insertions, 2 deletions

diff --git a/lib/Transforms/Vectorize/LoopVectorize.cpp b/lib/Transforms/Vectorize/LoopVectorize.cpp
index 317c1ffd85..8b5424f599 100644
--- a/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2965,8 +2965,9 @@ bool LoopVectorizationLegality::canVectorizeInstrs() {
       }
 
       // Check that the instruction return type is vectorizable.
-      if (!VectorType::isValidElementType(it->getType()) &&
-          !it->getType()->isVoidTy()) {
+      // Also, we can't vectorize extractelement instructions.
+      if ((!VectorType::isValidElementType(it->getType()) &&
+           !it->getType()->isVoidTy()) || isa<ExtractElementInst>(it)) {
         DEBUG(dbgs() << "LV: Found unvectorizable type.\n");
         return false;
       }