1 files changed, 9 insertions, 11 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index cb19c0a4e0f..4d85532a81b 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -475,7 +475,8 @@ namespace {
     SDValue reduceBuildVecToShuffle(SDNode *N);
     SDValue createBuildVecShuffle(const SDLoc &DL, SDNode *N,
                                   ArrayRef<int> VectorMask, SDValue VecIn1,
-                                  SDValue VecIn2, unsigned LeftIdx);
+                                  SDValue VecIn2, unsigned LeftIdx,
+                                  bool DidSplitVec);
     SDValue matchVSelectOpSizesWithSetCC(SDNode *Cast);
 
     /// Walk up chain skipping non-aliasing memory nodes,
@@ -16416,7 +16417,7 @@ SDValue DAGCombiner::reduceBuildVecExtToExtBuildVec(SDNode *N) {
 SDValue DAGCombiner::createBuildVecShuffle(const SDLoc &DL, SDNode *N,
                                            ArrayRef<int> VectorMask,
                                            SDValue VecIn1, SDValue VecIn2,
-                                           unsigned LeftIdx) {
+                                           unsigned LeftIdx, bool DidSplitVec) {
   MVT IdxTy = TLI.getVectorIdxTy(DAG.getDataLayout());
   SDValue ZeroIdx = DAG.getConstant(0, DL, IdxTy);
 
@@ -16424,17 +16425,12 @@ SDValue DAGCombiner::createBuildVecShuffle(const SDLoc &DL, SDNode *N,
   EVT InVT1 = VecIn1.getValueType();
   EVT InVT2 = VecIn2.getNode() ? VecIn2.getValueType() : InVT1;
 
-  unsigned Vec2Offset = 0;
   unsigned NumElems = VT.getVectorNumElements();
   unsigned ShuffleNumElems = NumElems;
 
-  // In case both the input vectors are extracted from same base
-  // vector we do not need extra addend (Vec2Offset) while
-  // computing shuffle mask.
-  if (!VecIn2 || !(VecIn1.getOpcode() == ISD::EXTRACT_SUBVECTOR) ||
-      !(VecIn2.getOpcode() == ISD::EXTRACT_SUBVECTOR) ||
-      !(VecIn1.getOperand(0) == VecIn2.getOperand(0)))
-    Vec2Offset = InVT1.getVectorNumElements();
+  // If we artificially split a vector in two already, then the offsets in the
+  // operands will all be based off of VecIn1, even those in VecIn2.
+  unsigned Vec2Offset = DidSplitVec ? 0 : InVT1.getVectorNumElements();
 
   // We can't generate a shuffle node with mismatched input and output types.
   // Try to make the types match the type of the output.
@@ -16693,6 +16689,7 @@ SDValue DAGCombiner::reduceBuildVecToShuffle(SDNode *N) {
   // vector, then split the vector efficiently based on the maximum
   // vector access index and adjust the VectorMask and
   // VecIn accordingly.
+  bool DidSplitVec = false;
   if (VecIn.size() == 2) {
     unsigned MaxIndex = 0;
     unsigned NearestPow2 = 0;
@@ -16723,6 +16720,7 @@ SDValue DAGCombiner::reduceBuildVecToShuffle(SDNode *N) {
         VecIn.pop_back();
         VecIn.push_back(VecIn1);
         VecIn.push_back(VecIn2);
+        DidSplitVec = true;
 
         for (unsigned i = 0; i < NumElems; i++) {
           if (VectorMask[i] <= 0)
@@ -16760,7 +16758,7 @@ SDValue DAGCombiner::reduceBuildVecToShuffle(SDNode *N) {
         (LeftIdx + 1) < VecIn.size() ? VecIn[LeftIdx + 1] : SDValue();
 
     if (SDValue Shuffle = createBuildVecShuffle(DL, N, VectorMask, VecLeft,
-                                                VecRight, LeftIdx))
+                                                VecRight, LeftIdx, DidSplitVec))
       Shuffles.push_back(Shuffle);
     else
       return SDValue();