[DAGCombine] Use FoldConstantArithmetic() to perform ((c1-A)+c2) -> (c1+c2)-A fold

Summary: No tests change, and i'm not sure how to test this, but it's better safe than sorry.

Reviewers: spatel, RKSimon, craig.topper, t.p.northover

Reviewed By: craig.topper

Subscribers: llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D62661

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@362130 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index d2045d764a0755cfc60b3a6754032a4f3cc2d387..49cd7596f5af414fb0036613f0be6a5f71d1e710 100644 (file)
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2164,10 +2164,10 @@ SDValue DAGCombiner::visitADDLike(SDNode *N) {
     // fold ((c1-A)+c2) -> (c1+c2)-A
     if (N0.getOpcode() == ISD::SUB &&
         isConstantOrConstantVector(N0.getOperand(0), /* NoOpaque */ true)) {
-      // FIXME: Adding 2 constants should be handled by FoldConstantArithmetic.
-      return DAG.getNode(ISD::SUB, DL, VT,
-                         DAG.getNode(ISD::ADD, DL, VT, N1, N0.getOperand(0)),
-                         N0.getOperand(1));
+      SDValue Add = DAG.FoldConstantArithmetic(ISD::ADD, DL, VT, N1.getNode(),
+                                               N0.getOperand(0).getNode());
+      assert(Add && "Constant folding failed");
+      return DAG.getNode(ISD::SUB, DL, VT, Add, N0.getOperand(1));
     }
 
     // add (sext i1 X), 1 -> zext (not i1 X)