diff options
Diffstat (limited to 'lib/CodeGen/SelectionDAG/DAGCombiner.cpp')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index a82410ae6a..3e5a446e6e 100644 --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -4298,11 +4298,19 @@ SDValue DAGCombiner::visitSIGN_EXTEND(SDNode *N) { if (isa<ConstantSDNode>(N0)) return DAG.getNode(ISD::SIGN_EXTEND, N->getDebugLoc(), VT, N0); - // fold (sext (sext x)) -> (sext x) - // fold (sext (aext x)) -> (sext x) - if (N0.getOpcode() == ISD::SIGN_EXTEND || N0.getOpcode() == ISD::ANY_EXTEND) - return DAG.getNode(ISD::SIGN_EXTEND, N->getDebugLoc(), VT, - N0.getOperand(0)); + // Folding (sext (sext x)) is obvious, but we do it only after the type + // legalization phase. When the sequence is like {(T1->T2), (T2->T3)} and + // T1 or T3 (or the both) are illegal types, the TypeLegalizer may not + // give a good sequence for the (T1->T3) pair. + // So we give a chance to target specific combiner to optimize T1->T2 and T2->T3 + // separately and may be fold them in a preceding of subsequent instruction. + if (Level >= AfterLegalizeTypes) { + // fold (sext (sext x)) -> (sext x) + // fold (sext (aext x)) -> (sext x) + if (N0.getOpcode() == ISD::SIGN_EXTEND || N0.getOpcode() == ISD::ANY_EXTEND) + return DAG.getNode(ISD::SIGN_EXTEND, N->getDebugLoc(), VT, + N0.getOperand(0)); + } if (N0.getOpcode() == ISD::TRUNCATE) { // fold (sext (truncate (load x))) -> (sext (smaller load x)) |