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fold (shl x, 1) -> (add x, x)

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25120 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng
2006-01-06 01:06:31 +00:00
parent a35ef6350d
commit da95a84a11
2 changed files with 3 additions and 20 deletions
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3
lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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@@ -1282,6 +1282,9 @@ SDOperand DAGCombiner::visitSHL(SDNode *N) {
// fold (shl x, 0) -> x
if (N1C && N1C->isNullValue())
return N0;
// fold (shl x, 1) -> (add x, x)
if (N1C && N1C->getValue() == 1)
return DAG.getNode(ISD::ADD, VT, N0, N0);
// if (shl x, c) is known to be zero, return 0
if (N1C && MaskedValueIsZero(SDOperand(N, 0), ~0ULL >> (64-OpSizeInBits),TLI))
return DAG.getConstant(0, VT);