Changes in directory llvm/lib/CodeGen/SelectionDAG:
DAGCombiner.cpp updated: 1.163 -> 1.164
---
Log message:
Compile this:
short test4(unsigned X) {
return (X >> 16);
}
to:
_test4:
movl 4(%esp), %eax
sarl $16, %eax
ret
instead of:
_test4:
movl $-65536, %eax
andl 4(%esp), %eax
sarl $16, %eax
ret
---
Diffs of the changes: (+5 -0)
DAGCombiner.cpp | 5 +++++
1 files changed, 5 insertions(+)
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.163
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.164
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.163 Sun May 7 20:35:01 2006
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Mon May 8 15:51:54 2006
@@ -1575,6 +1575,11 @@
}
}
+ // Simplify, based on bits shifted out of the LHS.
+ if (N1C && SimplifyDemandedBits(SDOperand(N, 0)))
+ return SDOperand(N, 0);
+
+
// If the sign bit is known to be zero, switch this to a SRL.
if (TLI.MaskedValueIsZero(N0, MVT::getIntVTSignBit(VT)))
return DAG.getNode(ISD::SRL, VT, N0, N1);
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