diff options
Diffstat (limited to 'llvm/lib')
| -rw-r--r-- | llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp index 8e0e0fe2822..8388a95b8cf 100644 --- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp +++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp @@ -4362,6 +4362,22 @@ SDValue DAGCombiner::visitSHL(SDNode *N) { } } + // fold (shl (sr[la] exact X, C1), C2) -> (shl X, (C2-C1)) if C1 <= C2 + // fold (shl (sr[la] exact X, C1), C2) -> (sr[la] X, (C2-C1)) if C1 > C2 + if (N1C && (N0.getOpcode() == ISD::SRL || N0.getOpcode() == ISD::SRA) && + cast<BinaryWithFlagsSDNode>(N0)->Flags.hasExact()) { + if (ConstantSDNode *N0C1 = isConstOrConstSplat(N0.getOperand(1))) { + uint64_t C1 = N0C1->getZExtValue(); + uint64_t C2 = N1C->getZExtValue(); + SDLoc DL(N); + if (C1 <= C2) + return DAG.getNode(ISD::SHL, DL, VT, N0.getOperand(0), + DAG.getConstant(C2 - C1, DL, N1.getValueType())); + return DAG.getNode(N0.getOpcode(), DL, VT, N0.getOperand(0), + DAG.getConstant(C1 - C2, DL, N1.getValueType())); + } + } + // fold (shl (srl x, c1), c2) -> (and (shl x, (sub c2, c1), MASK) or // (and (srl x, (sub c1, c2), MASK) // Only fold this if the inner shift has no other uses -- if it does, folding |
