Add a few more transformations.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60391 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 6b35126..629e22d 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1013,6 +1013,30 @@
// fold ((B-A)+A) -> B
if (N0.getOpcode() == ISD::SUB && N1 == N0.getOperand(1))
return N0.getOperand(0);
+ // fold (A+(B-(A+C))) to (B-C)
+ if (N1.getOpcode() == ISD::SUB && N1.getOperand(1).getOpcode() == ISD::ADD &&
+ N0 == N1.getOperand(1).getOperand(0)) {
+ return DAG.getNode(ISD::SUB, VT, N1.getOperand(0),
+ N1.getOperand(1).getOperand(1));
+ }
+ // fold (A+(B-(C+A))) to (B-C)
+ if (N1.getOpcode() == ISD::SUB && N1.getOperand(1).getOpcode() == ISD::ADD &&
+ N0 == N1.getOperand(1).getOperand(1)) {
+ return DAG.getNode(ISD::SUB, VT, N1.getOperand(0),
+ N1.getOperand(1).getOperand(0));
+ }
+ // fold (A-B)+(C-D) to (A+C)-(B+D) when A or C is constant
+ if (N0.getOpcode() == ISD::SUB && N1.getOpcode() == ISD::SUB) {
+ SDValue N00 = N0.getOperand(0);
+ SDValue N01 = N0.getOperand(1);
+ SDValue N10 = N1.getOperand(0);
+ SDValue N11 = N1.getOperand(1);
+ if (isa<ConstantSDNode>(N00) || isa<ConstantSDNode>(N10)) {
+ return DAG.getNode(ISD::SUB, VT,
+ DAG.getNode(ISD::ADD, VT, N00, N10),
+ DAG.getNode(ISD::ADD, VT, N01, N11));
+ }
+ }
if (!VT.isVector() && SimplifyDemandedBits(SDValue(N, 0)))
return SDValue(N, 0);