Hello Marc, On Oct 9, 2014, at 12:33 PM, Marc Glisse wrote: > If this is accepted, I will gladly prepare patches removing the unused > builtins and extending this to a few more operations (integer vectors in > particular). If this is not the direction we want to go, I'd like to hear it > clearly so I can move on...
As we discussed offlist, removing all the builtins would be problematic for Ada as they are the only medium allowing flexible access to vector instructions (aside autovectorization) for users. Today, the model is very simple: people who want to build on top of vector operations just bind to the builtins they need and expose higher level interfaces if they like, provided proper type definitions (see g-sse.ads for example). We could provide an Ada version of the standard APIs for example, as we do for Altivec on powerpc, and we have offered this capability out of customer requests. Without the builtins, we'd need to define syntax + semantics for vector operations in the language. While this is an interesting perspective, we don't have that today and this would be a fair amount of non-trivial work I'm afraid, not something we can take on just like that. Note that this doesn't mean that we need all the builtins to remain there. Just at least one of those providing access to a given machine insn at some point. We can implement various sorts of always_inline wrappers to perform type conversions as needed, and builtins are understood as very low level devices so changes in the interface aren't an issue. The real issue would be if access to a given insn becomes impossible out of the removals. Thanks! With Kind Regards, Olivier
