SLPVectorizer: An in-tree vectorized entry cannot also be a scalar external use

We were creating external uses for scalar values in MustGather entries that also
had a ScalarToTreeEntry (they also are present in a vectorized tuple). This
meant we would keep a value 'alive' as a scalar and vectorized causing havoc.
This is not necessary because when we create a MustGather vector we explicitly
create external uses entries for the insertelement instructions of the
MustGather vector elements.

Fixes PR18129.

radar://15582184

llvm-svn: 196508

1 files changed, 1 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 966fca766c7..2af3701b900 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -564,10 +564,8 @@ void BoUpSLP::buildTree(ArrayRef<Value *> Roots, ValueSet *Rdx) {
            UE = Scalar->use_end(); User != UE; ++User) {
         DEBUG(dbgs() << "SLP: Checking user:" << **User << ".\n");
 
-        bool Gathered = MustGather.count(*User);
-
         // Skip in-tree scalars that become vectors.
-        if (ScalarToTreeEntry.count(*User) && !Gathered) {
+        if (ScalarToTreeEntry.count(*User)) {
           DEBUG(dbgs() << "SLP: \tInternal user will be removed:" <<
                 **User << ".\n");
           int Idx = ScalarToTreeEntry[*User]; (void) Idx;
@@ -1641,8 +1639,6 @@ Value *BoUpSLP::vectorizeTree() {
         for (Value::use_iterator User = Scalar->use_begin(),
              UE = Scalar->use_end(); User != UE; ++User) {
           DEBUG(dbgs() << "SLP: \tvalidating user:" << **User << ".\n");
-          assert(!MustGather.count(*User) &&
-                 "Replacing gathered value with undef");
 
           assert((ScalarToTreeEntry.count(*User) ||
                   // It is legal to replace the reduction users by undef.