[LV] Minor savings to Sink casts to unravel first order recurrence

Two minor savings: avoid copying the SinkAfter map and avoid moving a cast if it
is not needed.

Differential Revision: https://reviews.llvm.org/D36408

llvm-svn: 310910

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 5c640542e9a..adde81984c2 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -7655,7 +7655,7 @@ void LoopVectorizationPlanner::executePlan(InnerLoopVectorizer &ILV) {
   // 2. Copy and widen instructions from the old loop into the new loop.
 
   // Move instructions to handle first-order recurrences.
-  DenseMap<Instruction *, Instruction *> SinkAfter = Legal->getSinkAfter();
+  DenseMap<Instruction *, Instruction *> &SinkAfter = Legal->getSinkAfter();
   for (auto &Entry : SinkAfter) {
     Entry.first->removeFromParent();
     Entry.first->insertAfter(Entry.second);