Fix a dagga combiner bug: avoid creating illegal constant.
Is this really a winning transformation?
fold (shl (srl x, c1), c2) -> (shl (and x, (shl -1, c1)), (sub c2, c1)) or
(srl (and x, (shl -1, c1)), (sub c1, c2))
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76535 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 4ff2a3a..370054d 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2475,15 +2475,18 @@
if (N1C && N0.getOpcode() == ISD::SRL &&
N0.getOperand(1).getOpcode() == ISD::Constant) {
uint64_t c1 = cast<ConstantSDNode>(N0.getOperand(1))->getZExtValue();
- uint64_t c2 = N1C->getZExtValue();
- SDValue Mask = DAG.getNode(ISD::AND, N0.getDebugLoc(), VT, N0.getOperand(0),
- DAG.getConstant(~0ULL << c1, VT));
- if (c2 > c1)
- return DAG.getNode(ISD::SHL, N->getDebugLoc(), VT, Mask,
- DAG.getConstant(c2-c1, N1.getValueType()));
- else
- return DAG.getNode(ISD::SRL, N->getDebugLoc(), VT, Mask,
- DAG.getConstant(c1-c2, N1.getValueType()));
+ if (c1 < VT.getSizeInBits()) {
+ uint64_t c2 = N1C->getZExtValue();
+ SDValue Mask = DAG.getNode(ISD::AND, N0.getDebugLoc(), VT,
+ N0.getOperand(0),
+ DAG.getConstant(~0ULL << c1, VT));
+ if (c2 > c1)
+ return DAG.getNode(ISD::SHL, N->getDebugLoc(), VT, Mask,
+ DAG.getConstant(c2-c1, N1.getValueType()));
+ else
+ return DAG.getNode(ISD::SRL, N->getDebugLoc(), VT, Mask,
+ DAG.getConstant(c1-c2, N1.getValueType()));
+ }
}
// fold (shl (sra x, c1), c1) -> (and x, (shl -1, c1))
if (N1C && N0.getOpcode() == ISD::SRA && N1 == N0.getOperand(1))