[llvm] r366914 - [SDAG] convert (sub x, 1) to (add x, -1) in ctpop expansion; NFC

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Wed Jul 24 08:43:50 2019
New Revision: 366914

URL: http://llvm.org/viewvc/llvm-project?rev=366914&view=rev
Log:
[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.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp?rev=366914&r1=366913&r2=366914&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp Wed Jul 24 08:43:50 2019
@@ -2876,9 +2876,9 @@ SDValue TargetLowering::SimplifySetCC(EV
       // (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);
       }