[PATCH] D76612: [Matrix] Add draft specification for matrix support in Clang.

[Sjoerd Meijer via Phabricator via cfe-commits]

SjoerdMeijer added inline comments.


================
Comment at: clang/docs/MatrixTypes.rst:27
+internal layout, overall size and alignment are implementation-defined.
+A *matrix element type* must be a real type (as in C99 6.2.5p17) excluding
+enumeration types or an implementation-defined half-precision floating point
----------------
fhahn wrote:
> SjoerdMeijer wrote:
> > above you're using *element type* and here *matrix element type*. Since hopefully we're talking about the same things, "matrix *element type*" would be more consistent.
> > 
> > But this is just a nit, my main question is about the types:
> > why not e.g. define this to be the C11 types, that include _FloatN types, so that we can include N=16? Or is this intentionally omitted? I haven't even checked if this is supported in the architecture extension, but might make sense? And also, an element type cannot be an integer type? 
> > 
> >  
> > above you're using *element type* and here *matrix element type*. Since hopefully we're talking about the same things, "matrix *element type*" would be more consistent.
> 
> Yes it is referring to the same thing. I had a look at most uses, and in most cases `element type` is used to refer to the element type of a given matrix type. In that context it seems a bit verbose to use `matrix element type`, although I am more than happy to change that if it helps with clarifying things.
> 
> I intentionally used `matrix element type` in `Arithmetic Conversions`, because there it is standing on its own and refers exactly to the set of types defined as valid matrix element types here.
> 
> > why not e.g. define this to be the C11 types, that include _FloatN types, so that we can include N=16? Or is this intentionally omitted? I haven't even checked if this is supported in the architecture extension, but might make sense?
> 
> I couldn't find any reference to _FloatN types in the C11 draft version I checked. Do you by any chance have a reference to the _FloatN types?
> 
> > And also, an element type cannot be an integer type?
> 
> The current definition should include it (real types include integer and real floating point types according to  C99 6.2.5p17). I don't think there is any reason to exclude them I think.
>>    why not e.g. define this to be the C11 types, that include _FloatN types, so that we can include N=16? Or is this intentionally omitted? I haven't even checked if this is supported in the architecture extension, but might make sense?
>>
> I couldn't find any reference to _FloatN types in the C11 draft version I checked. Do you by any chance have a reference to the _FloatN types?

Sorry, I was a bit imprecise here, it's an extension of C11: ISO/IEC TS 18661-3:2015.
My thinking was it would be cool to support the "proper" half-precision type. I thought about this, because of "or an implementation-defined half-precision" mentioned just below here, of which probably __fp16 is an example.  If you refer to the C99 types, you probably don't even need to mention this (although it won't do any harm)?

>>  And also, an element type cannot be an integer type?
>
> The current definition should include it (real types include integer and real floating point types according to C99 6.2.5p17). I don't think there is any reason to exclude them I think.

Ok, cheers, wrote this from memory (forgot this), and didn't check the standard.


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