Changes in directory llvm/lib/CodeGen/SelectionDAG:
DAGCombiner.cpp updated: 1.157 -> 1.158
---
Log message:
Shrink shifts when possible.
---
Diffs of the changes: (+12 -0)
DAGCombiner.cpp | 12 ++++++++++++
1 files changed, 12 insertions(+)
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.157
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.158
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.157 Fri May 5 16:34:35 2006
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Fri May 5 17:53:17 2006
@@ -1615,6 +1615,18 @@
DAG.getConstant(c1 + c2, N1.getValueType()));
}
+ // fold (srl (anyextend x), c) -> (anyextend (srl x, c))
+ if (N1C && N0.getOpcode() == ISD::ANY_EXTEND) {
+ // Shifting in all undef bits?
+ MVT::ValueType SmallVT = N0.getOperand(0).getValueType();
+ if (N1C->getValue() >= MVT::getSizeInBits(SmallVT))
+ return DAG.getNode(ISD::UNDEF, VT);
+
+ SDOperand SmallShift = DAG.getNode(ISD::SRL, SmallVT, N0.getOperand(0),
N1);
+ AddToWorkList(SmallShift.Val);
+ return DAG.getNode(ISD::ANY_EXTEND, VT, SmallShift);
+ }
+
// fold (srl (ctlz x), "5") -> x iff x has one bit set (the low bit).
if (N1C && N0.getOpcode() == ISD::CTLZ &&
N1C->getValue() == Log2_32(MVT::getSizeInBits(VT))) {
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