A new dag combine; several permutations of this
are there under ADD, this one was missing.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61107 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 6538417..783bfce 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1178,6 +1178,12 @@
// fold (A+B)-B -> A
if (N0.getOpcode() == ISD::ADD && N0.getOperand(1) == N1)
return N0.getOperand(0);
+ // fold ((A+(B-C))-B) -> A-C
+ if (N0.getOpcode() == ISD::ADD &&
+ N0.getOperand(1).getOpcode() == ISD::SUB &&
+ N0.getOperand(1).getOperand(0) == N1)
+ return DAG.getNode(ISD::SUB, VT, N0.getOperand(0),
+ N0.getOperand(1).getOperand(1));
// fold (sub x, (select cc, 0, c)) -> (select cc, x, (sub, x, c))
if (N1.getOpcode() == ISD::SELECT && N1.getNode()->hasOneUse()) {
SDValue Result = combineSelectAndUse(N, N1, N0, DAG, TLI, LegalOperations);