[LLVMdev] Boxing and vectors

[Tomas Lindquist Olsen]

All x86-64 processors support SSE and SSE2 (most have SSE3 as well).

On Nov 30, 2007 1:09 AM, Gordon Henriksen <gordonhenriksen at mac.com> wrote:
> On Nov 29, 2007, at 16:06, Jon Harrop wrote:
>
> > So I now have a working first-order language that uses conventional
> > boxing to handle polymorphism and with ints, floats and ('a -> 'a)
> > functions.
>
> Cool.
>
> > After a huge amount of detailed benchmarking in OCaml and F# I have
> > decided that it is very important to be able to unbox complex
> > numbers but no other compound types. As LLVM provides a vector type
> > for power-of-two dimensionalities that compiles to efficient
> > parallel code, I'd like to know if I can store them unboxed in a way
> > that is equivalent to my ints, floats and function pointers, i.e.
> > can I cast to and from them or must I add an indirection via a
> > pointer?
>
> Bitcast simply depends on storage size. If two first-class types are
> of the same size, you can bitcast. If not, you can't. Pointers are the
> only exception; those require a combination bitcast/inttoptr or
> ptrtoint/bitcast to cover all possible conversions.
>
> On 32-bit platforms, these first-class types are bitcastable to one
> another:
>
> i32, float, any*, <2 x i16>, <4 x i8>
>
> On 64-bit platforms:
>
> i64, double, any*, <2 x float>, <2 x i32>, <4 x i16>, <8 x i8>
>
> So to utilize erasure-based polymorphism (as in Java or Ocaml), only
> single-precision floating-point complex numbers can be unboxed, and
> only on 64-bit hosts. If you're only interested in complex, would be
> to compile two copies of each polymorphic function, one for complex
> numbers, and the other for all other values. To more generally support
> unboxing, you'll need to look more towards .NET generics and C++
> templates for guidance.
>
> > Also, do these vectors give significant performance improvements on
> > x86-64 hardware or are they only good for x86+SSE and relatives?
>
>
> Are there (m)any x64 processors without SSE?
>
> — Gordon
>
>
>
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