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...'E', there is no need to update the parts of LSR that analyze / modify registers to preserve correctness. Note: this type of "opaque" node also can be used to force the SCEV expander to generate a particular sequence of expressions; something that is achieved by the "expand(getSCEVUnknown(expand(Op)))" idiom in LSR currently. So far I'm leaning towards the second approach, but given that it would be a substantial change (though potentially useful elsewhere), I'd like to hear what others think before diving in. -- Sanjoy [1]: http://lists.llvm.org/pipermail/llvm-de...