Changes in directory llvm/lib/CodeGen/SelectionDAG:
DAGCombiner.cpp updated: 1.110 -> 1.111
---
Log message:
fold (sra (sra x, c1), c2) -> (sra x, c1+c2)
---
Diffs of the changes: (+11 -3)
DAGCombiner.cpp | 14 +++++++++++---
1 files changed, 11 insertions(+), 3 deletions(-)
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
diff -u llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.110
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.111
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp:1.110 Sun Feb 26 18:39:31 2006
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue Feb 28 00:23:04 2006
@@ -23,9 +23,6 @@
// FIXME: mul (x, const) -> shifts + adds
// FIXME: undef values
// FIXME: make truncate see through SIGN_EXTEND and AND
-// FIXME: (sra (sra x, c1), c2) -> (sra x, c1+c2)
-// FIXME: verify that getNode can't return extends with an operand whose type
-// is >= to that of the extend.
// FIXME: divide by zero is currently left unfolded. do we want to turn this
// into an undef?
// FIXME: select ne (select cc, 1, 0), 0, true, false -> select cc, true, false
@@ -1367,6 +1364,17 @@
return DAG.getNode(ISD::SIGN_EXTEND_INREG, VT, N0.getOperand(0),
DAG.getValueType(EVT));
}
+
+ // fold (sra (sra x, c1), c2) -> (sra x, c1+c2)
+ if (N1C && N0.getOpcode() == ISD::SRA) {
+ if (ConstantSDNode *C1 = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
+ unsigned Sum = N1C->getValue() + C1->getValue();
+ if (Sum >= MVT::getSizeInBits(VT)) Sum = MVT::getSizeInBits(VT)-1;
+ return DAG.getNode(ISD::SRA, VT, N0.getOperand(0),
+ DAG.getConstant(Sum, N1C->getValueType(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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