1 files changed, 58 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 9a27cf36380..933898b17c8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -3805,6 +3805,38 @@ bool SelectionDAG::haveNoCommonBitsSet(SDValue A, SDValue B) const {
   return (computeKnownBits(A).Zero | computeKnownBits(B).Zero).isAllOnesValue();
 }
 
+static SDValue FoldBUILD_VECTOR(const SDLoc &DL, EVT VT,
+                                ArrayRef<SDValue> Ops,
+                                SelectionDAG &DAG) {
+  int NumOps = Ops.size();
+  assert(NumOps != 0 && "Can't build an empty vector!");
+  assert(VT.getVectorNumElements() == NumOps &&
+         "Incorrect element count in BUILD_VECTOR!");
+
+  // BUILD_VECTOR of UNDEFs is UNDEF.
+  if (llvm::all_of(Ops, [](SDValue Op) { return Op.isUndef(); }))
+    return DAG.getUNDEF(VT);
+
+  // BUILD_VECTOR of seq extract/insert from the same vector + type is Identity.
+  SDValue IdentitySrc;
+  bool IsIdentity = true;
+  for (int i = 0; i != NumOps; ++i) {
+    if (Ops[i].getOpcode() != ISD::EXTRACT_VECTOR_ELT ||
+        Ops[i].getOperand(0).getValueType() != VT ||
+        (IdentitySrc && Ops[i].getOperand(0) != IdentitySrc) ||
+        !isa<ConstantSDNode>(Ops[i].getOperand(1)) ||
+        cast<ConstantSDNode>(Ops[i].getOperand(1))->getAPIntValue() != i) {
+      IsIdentity = false;
+      break;
+    }
+    IdentitySrc = Ops[i].getOperand(0);
+  }
+  if (IsIdentity)
+    return IdentitySrc;
+
+  return SDValue();
+}
+
 static SDValue FoldCONCAT_VECTORS(const SDLoc &DL, EVT VT,
                                   ArrayRef<SDValue> Ops,
                                   SelectionDAG &DAG) {
@@ -4059,6 +4091,13 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
   case ISD::MERGE_VALUES:
   case ISD::CONCAT_VECTORS:
     return Operand;         // Factor, merge or concat of one node?  No need.
+  case ISD::BUILD_VECTOR: {
+    // Attempt to simplify BUILD_VECTOR.
+    SDValue Ops[] = {Operand};
+    if (SDValue V = FoldBUILD_VECTOR(DL, VT, Ops, *this))
+      return V;
+    break;
+  }
   case ISD::FP_ROUND: llvm_unreachable("Invalid method to make FP_ROUND node");
   case ISD::FP_EXTEND:
     assert(VT.isFloatingPoint() &&
@@ -4548,6 +4587,13 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
     if (N2.getOpcode() == ISD::EntryToken) return N1;
     if (N1 == N2) return N1;
     break;
+  case ISD::BUILD_VECTOR: {
+    // Attempt to simplify BUILD_VECTOR.
+    SDValue Ops[] = {N1, N2};
+    if (SDValue V = FoldBUILD_VECTOR(DL, VT, Ops, *this))
+      return V;
+    break;
+  }
   case ISD::CONCAT_VECTORS: {
     // Attempt to fold CONCAT_VECTORS into BUILD_VECTOR or UNDEF.
     SDValue Ops[] = {N1, N2};
@@ -5019,6 +5065,13 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
     }
     break;
   }
+  case ISD::BUILD_VECTOR: {
+    // Attempt to simplify BUILD_VECTOR.
+    SDValue Ops[] = {N1, N2, N3};
+    if (SDValue V = FoldBUILD_VECTOR(DL, VT, Ops, *this))
+      return V;
+    break;
+  }
   case ISD::CONCAT_VECTORS: {
     // Attempt to fold CONCAT_VECTORS into BUILD_VECTOR or UNDEF.
     SDValue Ops[] = {N1, N2, N3};
@@ -6788,6 +6841,11 @@ SDValue SelectionDAG::getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
 
   switch (Opcode) {
   default: break;
+  case ISD::BUILD_VECTOR:
+    // Attempt to simplify BUILD_VECTOR.
+    if (SDValue V = FoldBUILD_VECTOR(DL, VT, Ops, *this))
+      return V;
+    break;
   case ISD::CONCAT_VECTORS:
     // Attempt to fold CONCAT_VECTORS into BUILD_VECTOR or UNDEF.
     if (SDValue V = FoldCONCAT_VECTORS(DL, VT, Ops, *this))