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[X86] Improve comment

llvm-svn: 217885
This commit is contained in:
Adam Nemet 2014-09-16 17:14:10 +00:00
parent 735d692499
commit 3c3ce2d2ee

View File

@ -775,9 +775,10 @@ static void InsertDAGNode(SelectionDAG &DAG, SDValue Pos, SDValue N) {
}
}
// Transform "(X >> (8-C1)) & C2" to "(X >> 8) & 0xff)" if safe. This
// allows us to convert the shift and and into an h-register extract and
// a scaled index. Returns false if the simplification is performed.
// Transform "(X >> (8-C1)) & (0xff << C1)" to "((X >> 8) & 0xff) << C1" if
// safe. This allows us to convert the shift and and into an h-register
// extract and a scaled index. Returns false if the simplification is
// performed.
static bool FoldMaskAndShiftToExtract(SelectionDAG &DAG, SDValue N,
uint64_t Mask,
SDValue Shift, SDValue X,