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Code simplification.

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llvm-svn: 51345
This commit is contained in:
Dan Gohman 2008-05-20 20:56:33 +00:00
parent 7d9e5793c5
commit 287e750e64
1 changed files with 4 additions and 6 deletions
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10
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@ -2776,20 +2776,18 @@ SDOperand DAGCombiner::visitSIGN_EXTEND(SDNode *N) {
if (N0.getOpcode() == ISD::SIGN_EXTEND || N0.getOpcode() == ISD::ANY_EXTEND)
return DAG.getNode(ISD::SIGN_EXTEND, VT, N0.getOperand(0));
// fold (sext (truncate (load x))) -> (sext (smaller load x))
// fold (sext (truncate (srl (load x), c))) -> (sext (smaller load (x+c/n)))
if (N0.getOpcode() == ISD::TRUNCATE) {
// fold (sext (truncate (load x))) -> (sext (smaller load x))
// fold (sext (truncate (srl (load x), c))) -> (sext (smaller load (x+c/n)))
SDOperand NarrowLoad = ReduceLoadWidth(N0.Val);
if (NarrowLoad.Val) {
if (NarrowLoad.Val != N0.Val)
CombineTo(N0.Val, NarrowLoad);
return DAG.getNode(ISD::SIGN_EXTEND, VT, NarrowLoad);
}
}
// See if the value being truncated is already sign extended. If so, just
// eliminate the trunc/sext pair.
if (N0.getOpcode() == ISD::TRUNCATE) {
// See if the value being truncated is already sign extended. If so, just
// eliminate the trunc/sext pair.
SDOperand Op = N0.getOperand(0);
unsigned OpBits = MVT::getSizeInBits(Op.getValueType());
unsigned MidBits = MVT::getSizeInBits(N0.getValueType());