[llvm] [X86][APX] Optimize usub.sat(X, 1) to cmp+adc with NDD (PR #208475)

[Phoebe Wang via llvm-commits]

================
@@ -29644,6 +29650,22 @@ static SDValue LowerADDSAT_SUBSAT(SDValue Op, SelectionDAG &DAG,
   unsigned Opcode = Op.getOpcode();
   SDLoc DL(Op);
 
+  if (Opcode == ISD::USUBSAT && !VT.isVector() && Subtarget.hasNDD()) {
+    if (auto *C = dyn_cast<ConstantSDNode>(Y)) {
+      if (C->isOne()) {
----------------
phoebewang wrote:

isOneConstant?

https://github.com/llvm/llvm-project/pull/208475