diff options
Diffstat (limited to 'llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
-rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 7 |
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). |