[SelectionDAG] combine vextract (v1iX extract_subvector(vNiX, Idx))

into vextract(vNiX,Idx) when creating vextract with getNode().
This case appeared in AVX512 after fixing pr33349 in r310552.

Differential revision: https://reviews.llvm.org/D36571

llvm-svn: 310828

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index b37704946a0..0ef8adaabbb 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -4373,6 +4373,15 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
         return getNode(ISD::EXTRACT_VECTOR_ELT, DL, VT, N1.getOperand(0), N2);
       }
     }
+
+    // EXTRACT_VECTOR_ELT of v1iX EXTRACT_SUBVECTOR could be formed
+    // when vector types are scalarized and v1iX is legal.
+    // vextract (v1iX extract_subvector(vNiX, Idx)) -> vextract(vNiX,Idx)
+    if (N1.getOpcode() == ISD::EXTRACT_SUBVECTOR &&
+        N1.getValueType().getVectorNumElements() == 1) {
+      return getNode(ISD::EXTRACT_VECTOR_ELT, DL, VT, N1.getOperand(0),
+                     N1.getOperand(1));
+    }
     break;
   case ISD::EXTRACT_ELEMENT:
     assert(N2C && (unsigned)N2C->getZExtValue() < 2 && "Bad EXTRACT_ELEMENT!");