[X86][AVX] insert_subvector(bitcast(v), bitcast(s), c1) -> bitcast(insert_subvector(v,s,c2))

Similar to what we already do in DAGCombiner, but this version also handles bitcasts from types with different scalar sizes, which x86 is better at handling.

Differential Revision: https://reviews.llvm.org/D57514

llvm-svn: 352773

1 files changed, 36 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 9bc3d482074..da479eb692c 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -41573,6 +41573,42 @@ static SDValue combineInsertSubvector(SDNode *N, SelectionDAG &DAG,
     }
   }
 
+  // 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))
+  // TODO: Move this to generic - which only supports same scalar sizes.
+  if ((Vec.isUndef() || Vec.getOpcode() == ISD::BITCAST) &&
+      SubVec.getOpcode() == ISD::BITCAST) {
+    SDValue VecSrc = peekThroughBitcasts(Vec);
+    SDValue SubVecSrc = peekThroughBitcasts(SubVec);
+    MVT VecSrcSVT = VecSrc.getSimpleValueType().getScalarType();
+    MVT SubVecSrcSVT = SubVecSrc.getSimpleValueType().getScalarType();
+    if (Vec.isUndef() || VecSrcSVT == SubVecSrcSVT) {
+      MVT NewOpVT;
+      SDValue NewIdx;
+      unsigned NumElts = OpVT.getVectorNumElements();
+      unsigned EltSizeInBits = OpVT.getScalarSizeInBits();
+      if ((EltSizeInBits % SubVecSrcSVT.getSizeInBits()) == 0) {
+        unsigned Scale = EltSizeInBits / SubVecSrcSVT.getSizeInBits();
+        NewOpVT = MVT::getVectorVT(SubVecSrcSVT, NumElts * Scale);
+        NewIdx = DAG.getIntPtrConstant(IdxVal * Scale, dl);
+      } else if ((SubVecSrcSVT.getSizeInBits() % EltSizeInBits) == 0) {
+        unsigned Scale = SubVecSrcSVT.getSizeInBits() / EltSizeInBits;
+        if ((IdxVal % Scale) == 0) {
+          NewOpVT = MVT::getVectorVT(SubVecSrcSVT, NumElts / Scale);
+          NewIdx = DAG.getIntPtrConstant(IdxVal / Scale, dl);
+        }
+      }
+      if (NewIdx && DAG.getTargetLoweringInfo().isOperationLegal(
+                        ISD::INSERT_SUBVECTOR, NewOpVT)) {
+        SDValue Res = DAG.getBitcast(NewOpVT, VecSrc);
+        Res = DAG.getNode(ISD::INSERT_SUBVECTOR, dl, NewOpVT, Res, SubVecSrc,
+                          NewIdx);
+        return DAG.getBitcast(OpVT, Res);
+      }
+    }
+  }
+
   // Fold two 16-byte or 32-byte subvector loads into one 32-byte or 64-byte
   // load:
   // (insert_subvector (insert_subvector undef, (load16 addr), 0),