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Avoid creating shift-by-zero SDNodes in the common case of 

i8* getelementptr. DAGCombine eliminates these, but this is
a fairly common case.

llvm-svn: 55214
This commit is contained in:
Dan Gohman 2008-08-23 01:06:51 +00:00
parent 4e7713c04d
commit 95d1056831
1 changed files with 10 additions and 9 deletions
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19
llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
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@ -2814,16 +2814,17 @@ void SelectionDAGLowering::visitGetElementPtr(User &I) {
// If this is a multiply by a power of two, turn it into a shl
// immediately. This is a very common case.
if (isPowerOf2_64(ElementSize)) {
unsigned Amt = Log2_64(ElementSize);
IdxN = DAG.getNode(ISD::SHL, N.getValueType(), IdxN,
DAG.getConstant(Amt, TLI.getShiftAmountTy()));
N = DAG.getNode(ISD::ADD, N.getValueType(), N, IdxN);
continue;
if (ElementSize != 1) {
if (isPowerOf2_64(ElementSize)) {
unsigned Amt = Log2_64(ElementSize);
IdxN = DAG.getNode(ISD::SHL, N.getValueType(), IdxN,
DAG.getConstant(Amt, TLI.getShiftAmountTy()));
} else {
SDValue Scale = DAG.getIntPtrConstant(ElementSize);
IdxN = DAG.getNode(ISD::MUL, N.getValueType(), IdxN, Scale);
}
}
SDValue Scale = DAG.getIntPtrConstant(ElementSize);
IdxN = DAG.getNode(ISD::MUL, N.getValueType(), IdxN, Scale);
N = DAG.getNode(ISD::ADD, N.getValueType(), N, IdxN);
}
}