[DAGCombine] Fold insert_subvector(bitcast(x),bitcast(y),c1) -> bitcast(insert_subvector(x,y),c2)

Move this combine from x86 into generic DAGCombine, which currently only manages cases where the bitcast is between types of the same scalarsize.

Differential Revision: https://reviews.llvm.org/D59188

llvm-svn: 362324

1 files changed, 37 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 4ed17440abc..949c14f3ce4 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -18780,6 +18780,43 @@ SDValue DAGCombiner::visitINSERT_SUBVECTOR(SDNode *N) {
 
   unsigned InsIdx = cast<ConstantSDNode>(N2)->getZExtValue();
 
+  // Push subvector bitcasts to the output, adjusting the index as we go.
+  // insert_subvector(bitcast(v), bitcast(s), c1)
+  // -> bitcast(insert_subvector(v, s, c2))
+  if ((N0.isUndef() || N0.getOpcode() == ISD::BITCAST) &&
+      N1.getOpcode() == ISD::BITCAST) {
+    SDValue N0Src = peekThroughBitcasts(N0);
+    SDValue N1Src = peekThroughBitcasts(N1);
+    EVT N0SrcSVT = N0Src.getValueType().getScalarType();
+    EVT N1SrcSVT = N1Src.getValueType().getScalarType();
+    if ((N0.isUndef() || N0SrcSVT == N1SrcSVT) &&
+        N0Src.getValueType().isVector() && N1Src.getValueType().isVector()) {
+      EVT NewVT;
+      SDLoc DL(N);
+      SDValue NewIdx;
+      MVT IdxVT = TLI.getVectorIdxTy(DAG.getDataLayout());
+      LLVMContext &Ctx = *DAG.getContext();
+      unsigned NumElts = VT.getVectorNumElements();
+      unsigned EltSizeInBits = VT.getScalarSizeInBits();
+      if ((EltSizeInBits % N1SrcSVT.getSizeInBits()) == 0) {
+        unsigned Scale = EltSizeInBits / N1SrcSVT.getSizeInBits();
+        NewVT = EVT::getVectorVT(Ctx, N1SrcSVT, NumElts * Scale);
+        NewIdx = DAG.getConstant(InsIdx * Scale, DL, IdxVT);
+      } else if ((N1SrcSVT.getSizeInBits() % EltSizeInBits) == 0) {
+        unsigned Scale = N1SrcSVT.getSizeInBits() / EltSizeInBits;
+        if ((NumElts % Scale) == 0 && (InsIdx % Scale) == 0) {
+          NewVT = EVT::getVectorVT(Ctx, N1SrcSVT, NumElts / Scale);
+          NewIdx = DAG.getConstant(InsIdx / Scale, DL, IdxVT);
+        }
+      }
+      if (NewIdx && hasOperation(ISD::INSERT_SUBVECTOR, NewVT)) {
+        SDValue Res = DAG.getBitcast(NewVT, N0Src);
+        Res = DAG.getNode(ISD::INSERT_SUBVECTOR, DL, NewVT, Res, N1Src, NewIdx);
+        return DAG.getBitcast(VT, Res);
+      }
+    }
+  }
+
   // Canonicalize insert_subvector dag nodes.
   // Example:
   // (insert_subvector (insert_subvector A, Idx0), Idx1)