[SDAG] convert (sub x, 1) to (add x, -1) in ctpop expansion; NFC

We canonicalize to the add form, so create that directly for efficiency.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@366914 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/TargetLowering.cpp b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
index dc2348f6cb845f33b3a96ec4489843b51d5022b7..d6ac17e8e5e832392d6afbbd35b40c1985d63307 100644 (file)
--- a/lib/CodeGen/SelectionDAG/TargetLowering.cpp
+++ b/lib/CodeGen/SelectionDAG/TargetLowering.cpp
@@ -2876,9 +2876,9 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
       // (ctpop x) u< 2 -> (x & x-1) == 0
       // (ctpop x) u> 1 -> (x & x-1) != 0
       if ((Cond == ISD::SETULT && C1 == 2) || (Cond == ISD::SETUGT && C1 == 1)){
-        SDValue Sub = DAG.getNode(ISD::SUB, dl, CTVT, CTOp,
-                                  DAG.getConstant(1, dl, CTVT));
-        SDValue And = DAG.getNode(ISD::AND, dl, CTVT, CTOp, Sub);
+        SDValue NegOne = DAG.getAllOnesConstant(dl, CTVT);
+        SDValue Add = DAG.getNode(ISD::ADD, dl, CTVT, CTOp, NegOne);
+        SDValue And = DAG.getNode(ISD::AND, dl, CTVT, CTOp, Add);
         ISD::CondCode CC = Cond == ISD::SETULT ? ISD::SETEQ : ISD::SETNE;
         return DAG.getSetCC(dl, VT, And, DAG.getConstant(0, dl, CTVT), CC);
       }