DAGCombiner: StoreMerging: Fix bad index calculating when adjusting mismatching vector types

This fixes a case of bad index calculation when merging mismatching
vector types. This changes the existing code to just use the existing
extract_{subvector|element} and a bitcast (instead of bitcast first and
then newly created extract_xxx) so we don't need to adjust any indices
in the first place.

rdar://44584718

Differential Revision: https://reviews.llvm.org/D52681

llvm-svn: 343493

1 files changed, 8 insertions, 17 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 4ad84bc3f88..3872f2d0142 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -13916,26 +13916,17 @@ bool DAGCombiner::MergeStoresOfConstantsOrVecElts(
         if ((MemVT != Val.getValueType()) &&
             (Val.getOpcode() == ISD::EXTRACT_VECTOR_ELT ||
              Val.getOpcode() == ISD::EXTRACT_SUBVECTOR)) {
-          SDValue Vec = Val.getOperand(0);
           EVT MemVTScalarTy = MemVT.getScalarType();
-          SDValue Idx = Val.getOperand(1);
           // We may need to add a bitcast here to get types to line up.
-          if (MemVTScalarTy != Vec.getValueType()) {
-            unsigned Elts = Vec.getValueType().getSizeInBits() /
-                            MemVTScalarTy.getSizeInBits();
-            if (Val.getValueType().isVector() && MemVT.isVector()) {
-              unsigned IdxC = cast<ConstantSDNode>(Idx)->getZExtValue();
-              unsigned NewIdx =
-                  ((uint64_t)IdxC * MemVT.getVectorNumElements()) / Elts;
-              Idx = DAG.getConstant(NewIdx, SDLoc(Val), Idx.getValueType());
-            }
-            EVT NewVecTy =
-                EVT::getVectorVT(*DAG.getContext(), MemVTScalarTy, Elts);
-            Vec = DAG.getBitcast(NewVecTy, Vec);
+          if (MemVTScalarTy != Val.getValueType().getScalarType()) {
+            Val = DAG.getBitcast(MemVT, Val);
+          } else {
+            unsigned OpC = MemVT.isVector() ? ISD::EXTRACT_SUBVECTOR
+                                            : ISD::EXTRACT_VECTOR_ELT;
+            SDValue Vec = Val.getOperand(0);
+            SDValue Idx = Val.getOperand(1);
+            Val = DAG.getNode(OpC, SDLoc(Val), MemVT, Vec, Idx);
           }
-          auto OpC = (MemVT.isVector()) ? ISD::EXTRACT_SUBVECTOR
-                                        : ISD::EXTRACT_VECTOR_ELT;
-          Val = DAG.getNode(OpC, SDLoc(Val), MemVT, Vec, Idx);
         }
         Ops.push_back(Val);
       }