[CodeGen][X86] Don't scalarize vector saturating add/sub

Now that we have vector support for [US](ADD|SUB)O we no longer
need to scalarize when expanding [US](ADD|SUB)SAT.

This matches what the cost model already does.

Differential Revision: https://reviews.llvm.org/D57348

llvm-svn: 353651

1 files changed, 6 insertions, 15 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index 370e0d5a088..26c495507cf 100644
--- a/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -5385,6 +5385,11 @@ SDValue TargetLowering::expandAddSubSat(SDNode *Node, SelectionDAG &DAG) const {
   EVT VT = LHS.getValueType();
   SDLoc dl(Node);
 
+  assert(LHS.getValueType().isInteger() && "Expected operands to be integers");
+  assert(RHS.getValueType().isInteger() && "Expected operands to be integers");
+  assert(LHS.getValueType() == RHS.getValueType() &&
+         "Expected both operands to be the same type");
+
   // 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);
@@ -5397,11 +5402,6 @@ SDValue TargetLowering::expandAddSubSat(SDNode *Node, SelectionDAG &DAG) const {
     return DAG.getNode(ISD::ADD, dl, VT, Min, RHS);
   }
 
-  if (VT.isVector()) {
-    // TODO: Consider not scalarizing here.
-    return SDValue();
-  }
-
   unsigned OverflowOp;
   switch (Opcode) {
   case ISD::SADDSAT:
@@ -5421,16 +5421,7 @@ SDValue TargetLowering::expandAddSubSat(SDNode *Node, SelectionDAG &DAG) const {
                      "addition or subtraction node.");
   }
 
-  assert(LHS.getValueType().isScalarInteger() &&
-         "Expected operands to be integers. Vector of int arguments should "
-         "already be unrolled.");
-  assert(RHS.getValueType().isScalarInteger() &&
-         "Expected operands to be integers. Vector of int arguments should "
-         "already be unrolled.");
-  assert(LHS.getValueType() == RHS.getValueType() &&
-         "Expected both operands to be the same type");
-
-  unsigned BitWidth = LHS.getValueSizeInBits();
+  unsigned BitWidth = LHS.getScalarValueSizeInBits();
   EVT ResultType = LHS.getValueType();
   EVT BoolVT =
       getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(), ResultType);