2 files changed, 28 insertions, 4 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
index 6e0bc97e92b..4923a529c21 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorOps.cpp
@@ -141,6 +141,7 @@ class VectorLegalizer {
   SDValue ExpandFunnelShift(SDValue Op);
   SDValue ExpandROT(SDValue Op);
   SDValue ExpandFMINNUM_FMAXNUM(SDValue Op);
+  SDValue ExpandAddSubSat(SDValue Op);
   SDValue ExpandStrictFPOp(SDValue Op);
 
   /// Implements vector promotion.
@@ -777,6 +778,11 @@ SDValue VectorLegalizer::Expand(SDValue Op) {
   case ISD::FMINNUM:
   case ISD::FMAXNUM:
     return ExpandFMINNUM_FMAXNUM(Op);
+  case ISD::USUBSAT:
+  case ISD::SSUBSAT:
+  case ISD::UADDSAT:
+  case ISD::SADDSAT:
+    return ExpandAddSubSat(Op);
   case ISD::STRICT_FADD:
   case ISD::STRICT_FSUB:
   case ISD::STRICT_FMUL:
@@ -1206,6 +1212,12 @@ SDValue VectorLegalizer::ExpandFMINNUM_FMAXNUM(SDValue Op) {
   return DAG.UnrollVectorOp(Op.getNode());
 }
 
+SDValue VectorLegalizer::ExpandAddSubSat(SDValue Op) {
+  if (SDValue Expanded = TLI.expandAddSubSat(Op.getNode(), DAG))
+    return Expanded;
+  return DAG.UnrollVectorOp(Op.getNode());
+}
+
 SDValue VectorLegalizer::ExpandStrictFPOp(SDValue Op) {
   EVT VT = Op.getValueType();
   EVT EltVT = VT.getVectorElementType();
diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 3c757440367..a2f05c1e3ce 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -5277,6 +5277,22 @@ SDValue TargetLowering::lowerCmpEqZeroToCtlzSrl(SDValue Op,
 
 SDValue TargetLowering::expandAddSubSat(SDNode *Node, SelectionDAG &DAG) const {
   unsigned Opcode = Node->getOpcode();
+  SDValue LHS = Node->getOperand(0);
+  SDValue RHS = Node->getOperand(1);
+  EVT VT = LHS.getValueType();
+  SDLoc dl(Node);
+
+  // usub.sat(a, b) -> umax(a, b) - b
+  if (Opcode == ISD::USUBSAT && isOperationLegalOrCustom(ISD::UMAX, VT)) {
+    SDValue Max = DAG.getNode(ISD::UMAX, dl, VT, LHS, RHS);
+    return DAG.getNode(ISD::SUB, dl, VT, Max, RHS);
+  }
+
+  if (VT.isVector()) {
+    // TODO: Consider not scalarizing here.
+    return SDValue();
+  }
+
   unsigned OverflowOp;
   switch (Opcode) {
   case ISD::SADDSAT:
@@ -5295,11 +5311,7 @@ SDValue TargetLowering::expandAddSubSat(SDNode *Node, SelectionDAG &DAG) const {
     llvm_unreachable("Expected method to receive signed or unsigned saturation "
                      "addition or subtraction node.");
   }
-  assert(Node->getNumOperands() == 2 && "Expected node to have 2 operands.");
 
-  SDLoc dl(Node);
-  SDValue LHS = Node->getOperand(0);
-  SDValue RHS = Node->getOperand(1);
   assert(LHS.getValueType().isScalarInteger() &&
          "Expected operands to be integers. Vector of int arguments should "
          "already be unrolled.");