start on SIMD documentation

[Walter Bright]

On 1/13/2012 8:52 PM, Andrei Alexandrescu wrote:
> On 1/13/12 10:03 PM, Walter Bright wrote:
>> On 1/13/2012 7:03 PM, Andrei Alexandrescu wrote:
>>> How is that possibly different from what you have now?
>>
>> Intrinsic functions are today just a table lookup in the compiler.
>
> They're a table lookup if the operation is a compile-time constant. So this
> argument does not apply.
>
>> Template intrinsics currently do not exist, so more code needs to be
>> written for them.
>
> The same table lookup could be done, except in this case it would be more
> principled.

You and I are talking about different things.

The current compiler looks for intrinsics after all template functions are 
converted into real functions. The mangled name is looked up in a table to see if:

1. it is an intrinsic function

2. what is the corresponding expression node operator

Doing it for intrinsic functions would require either:

1. adding hundreds of function signatures to the table

2. moving the intrinsic detection to the template instantiation logic