From: Duncan Sands <baldrick@free.fr>
Date: Wed, 6 May 2009 11:29:50 +0000 (+0000)
Subject: Add generic expansion of SUB when ADD and XOR
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a9cad0e7e09e6d34de2fccb4f1294b7f0b8f3b68;p=oota-llvm.git

Add generic expansion of SUB when ADD and XOR
are legal.  Based on a patch by Micah Villmow.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71078 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index bdcad0a3b5e..ca5f962a869 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -3268,8 +3268,7 @@ SDValue SelectionDAGLegalize::LegalizeOp(SDValue Op) {
           OpToUse = ISD::UMUL_LOHI;
         }
         if (OpToUse) {
-          Result = SDValue(DAG.getNode(OpToUse, dl, VTs, Tmp1, Tmp2).getNode(),
-                           0);
+          Result = DAG.getNode(OpToUse, dl, VTs, Tmp1, Tmp2);
           break;
         }
       }
@@ -3289,16 +3288,21 @@ SDValue SelectionDAGLegalize::LegalizeOp(SDValue Op) {
       }
       if (Node->getOpcode() == ISD::SDIV &&
           TLI.isOperationLegalOrCustom(ISD::SDIVREM, VT)) {
-        Result = SDValue(DAG.getNode(ISD::SDIVREM, dl,
-                                     VTs, Tmp1, Tmp2).getNode(),
-                         0);
+        Result = DAG.getNode(ISD::SDIVREM, dl, VTs, Tmp1, Tmp2);
         break;
       }
       if (Node->getOpcode() == ISD::UDIV &&
           TLI.isOperationLegalOrCustom(ISD::UDIVREM, VT)) {
-        Result = SDValue(DAG.getNode(ISD::UDIVREM, dl,
-                                     VTs, Tmp1, Tmp2).getNode(),
-                         0);
+        Result = DAG.getNode(ISD::UDIVREM, dl, VTs, Tmp1, Tmp2);
+        break;
+      }
+      if (Node->getOpcode() == ISD::SUB &&
+          TLI.isOperationLegalOrCustom(ISD::ADD, VT) &&
+          TLI.isOperationLegalOrCustom(ISD::XOR, VT)) {
+        Tmp2 = DAG.getNode(ISD::XOR, dl, VT, Tmp2,
+               DAG.getConstant(APInt::getAllOnesValue(VT.getSizeInBits()), VT));
+        Tmp2 = DAG.getNode(ISD::ADD, dl, VT, Tmp2, DAG.getConstant(1, VT));
+        Result = DAG.getNode(ISD::ADD, dl, VT, Tmp1, Tmp2);
         break;
       }