diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 879a4100e210..5ebda953fbd3 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -3648,6 +3648,15 @@ SDOperand DAGCombiner::visitFP_ROUND(SDNode *N) { if (N0.getOpcode() == ISD::FP_EXTEND && VT == N0.getOperand(0).getValueType()) return N0.getOperand(0); + // fold (fp_round (fp_round x)) -> (fp_round x) + if (N0.getOpcode() == ISD::FP_ROUND) { + // This is a value preserving truncation if both round's are. + bool IsTrunc = N->getConstantOperandVal(1) == 1 && + N0.Val->getConstantOperandVal(1) == 1; + return DAG.getNode(ISD::FP_ROUND, VT, N0.getOperand(0), + DAG.getIntPtrConstant(IsTrunc)); + } + // fold (fp_round (copysign X, Y)) -> (copysign (fp_round X), Y) if (N0.getOpcode() == ISD::FCOPYSIGN && N0.Val->hasOneUse()) { SDOperand Tmp = DAG.getNode(ISD::FP_ROUND, VT, N0.getOperand(0), N1);