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From: Julian S. <js...@ac...> - 2011-11-07 08:25:30
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Hi Maynard, all, > > different approaches we could take to implement this support: > > 1. Use existing PowerPC support > > 2. Define new Iops (hopefully could get by with something less than 50) > > 3. Use the Iex_CCall type of IRExpr to invoke a helper that executes > > the I suspected this day would come. To be clear, I'm not per se opposed to new Iops. It's just that we already have zillions of them, so I'm a little wary of adding en mass to them, especially considering it's difficult to get rid of them later if they should turn out to be the wrong thing / not well thought out / whatever. Clearly (1) is impractical and (3), well, that might be doable, but you lose the ability to do much useful analysis on the resulting IR: Memcheck's V-bit analysis will simply worst-case it, so there's no opportunity to do any more sophisticated analysis. Also, doing one function call per machine operation is going to be slow. So new Iops look unavoidable in this case. What I would ask is, can you + the s390 folks make an initial proposal of the new Iops you need, with names, types and a summary of behaviour. The aim would be to come up with a minimal but efficient set of Iops that will support DFP on both Power and s390. Then we can mash it around and see how it looks. Also, some indication of how this relates to the Intel DFP support that Christian mentioned, would be useful. J |