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-rw-r--r--llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp8
1 files changed, 8 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a3f89a86fce..38494f4b241 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2470,6 +2470,14 @@ SDValue DAGCombiner::visitADDLikeCommutative(SDValue N0, SDValue N1,
if (SDValue V = foldAddSubMasked1(true, N0, N1, DAG, DL))
return V;
+ // Hoist one-use subtraction by constant: (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 Add = DAG.getNode(ISD::ADD, DL, VT, N0.getOperand(0), N1);
+ return DAG.getNode(ISD::SUB, DL, VT, Add, N0.getOperand(1));
+ }
+
// If the target's bool is represented as 0/1, prefer to make this 'sub 0/1'
// rather than 'add 0/-1' (the zext should get folded).
// add (sext i1 Y), X --> sub X, (zext i1 Y)
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