[SLP]PR39774: Update references of the replaced external instructions.

Summary:
An additional fix for PR39774. Need to update the references for the
RedcutionRoot instruction when it is replaced during the vectorization
phase to avoid compiler crash on reduction vectorization.

Reviewers: RKSimon, spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D55017

llvm-svn: 347997

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index a1c642e7344..87a861970d1 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -3643,6 +3643,8 @@ BoUpSLP::vectorizeTree(ExtraValueToDebugLocsMap &ExternallyUsedValues) {
       auto &Locs = ExternallyUsedValues[Scalar];
       ExternallyUsedValues.insert({Ex, Locs});
       ExternallyUsedValues.erase(Scalar);
+      // Required to update internally referenced instructions.
+      Scalar->replaceAllUsesWith(Ex);
       continue;
     }