Michael Matz wrote:
Apart from that I agree that in the case of conditional defs multiple ones might reach a use. I disagree for partial defs, if one dominates the other. For most cases (except register allocation) a partial def is just a complete killing def, which happens to leave some contents unchanged (by conceptually copying that part from what was in there before, hence the usual read-mod-write dependency from a partial def which generates also a use). But the use doesn't care for this, for all it knows that def is the one changing the contents, hence a use-def chain should not contain a def dominating other defs (partial or not). The relationship between both defs will be described by the use-def chain hanging off the implicit use generated by the partial def.
I completely agree, and I've tried very hard to argue that with Kenneth last year when I spotted this kind of bogosity in the dataflow code, but I got nowhere. I wish you better luck.
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