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-rw-r--r--llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp7
1 files changed, 7 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index c733c24d5d7..a3f89a86fce 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2990,6 +2990,13 @@ SDValue DAGCombiner::visitSUB(SDNode *N) {
SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, N0, N1.getOperand(0));
return DAG.getNode(ISD::SUB, DL, VT, Sub, N1.getOperand(1));
}
+ // (x - C) - y -> (x - y) - C
+ // This is necessary because SUB(X,C) -> ADD(X,-C) doesn't work for vectors.
+ if (N0.hasOneUse() && N0.getOpcode() == ISD::SUB &&
+ isConstantOrConstantVector(N0.getOperand(1))) {
+ SDValue Sub = DAG.getNode(ISD::SUB, DL, VT, N0.getOperand(0), N1);
+ return DAG.getNode(ISD::SUB, DL, VT, Sub, N0.getOperand(1));
+ }
// If the target's bool is represented as 0/-1, prefer to make this 'add 0/-1'
// rather than 'sub 0/1' (the sext should get folded).
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