[LV] Fix for PR38110, LV encountered llvm_unreachable()

Summary: truncateToMinimalBitWidths() doesn't handle all Instructions and the worst case is compiler crash via llvm_unreachable(). Fix is to add a case to handle PHINode and changed the worst case to NO-OP (from compiler crash).

Reviewers: sbaranga, mssimpso, hsaito

Reviewed By: hsaito

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D49461

llvm-svn: 337861

1 files changed, 3 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 802f38e13da..3c693f5d5ee 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -3276,7 +3276,7 @@ void InnerLoopVectorizer::truncateToMinimalBitwidths() {
             SI->getOperand(1), VectorType::get(ScalarTruncatedTy, Elements1));
 
         NewI = B.CreateShuffleVector(O0, O1, SI->getMask());
-      } else if (isa<LoadInst>(I)) {
+      } else if (isa<LoadInst>(I) || isa<PHINode>(I)) {
         // Don't do anything with the operands, just extend the result.
         continue;
       } else if (auto *IE = dyn_cast<InsertElementInst>(I)) {
@@ -3291,7 +3291,8 @@ void InnerLoopVectorizer::truncateToMinimalBitwidths() {
             EE->getOperand(0), VectorType::get(ScalarTruncatedTy, Elements));
         NewI = B.CreateExtractElement(O0, EE->getOperand(2));
       } else {
-        llvm_unreachable("Unhandled instruction type!");
+        // If we don't know what to do, be conservative and don't do anything.
+        continue;
       }
 
       // Lastly, extend the result.