diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 3fca3b45757..8b1b6bbce30 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -9019,6 +9019,17 @@ SDValue DAGCombiner::visitFP_ROUND(SDNode *N) { if (N0.getOpcode() == ISD::FP_ROUND) { const bool NIsTrunc = N->getConstantOperandVal(1) == 1; const bool N0IsTrunc = N0.getNode()->getConstantOperandVal(1) == 1; + + // Skip this folding if it results in an fp_round from f80 to f16. + // + // f80 to f16 always generates an expensive (and as yet, unimplemented) + // libcall to __truncxfhf2 instead of selecting native f16 conversion + // instructions from f32 or f64. Moreover, the first (value-preserving) + // fp_round from f80 to either f32 or f64 may become a NOP in platforms like + // x86. + if (N0.getOperand(0).getValueType() == MVT::f80 && VT == MVT::f16) + return SDValue(); + // If the first fp_round isn't a value preserving truncation, it might // introduce a tie in the second fp_round, that wouldn't occur in the // single-step fp_round we want to fold to. |
