One more permutation of subtracting off a base value.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@61361 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 783bfce..e3525df 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -1184,6 +1184,12 @@
N0.getOperand(1).getOperand(0) == N1)
return DAG.getNode(ISD::SUB, VT, N0.getOperand(0),
N0.getOperand(1).getOperand(1));
+ // fold ((A-(B-C))-C) -> A-B
+ if (N0.getOpcode() == ISD::SUB &&
+ N0.getOperand(1).getOpcode() == ISD::SUB &&
+ N0.getOperand(1).getOperand(1) == N1)
+ return DAG.getNode(ISD::SUB, VT, N0.getOperand(0),
+ N0.getOperand(1).getOperand(0));
// 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);