diff options
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
-rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 8 |
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) |