[LLVMdev] LLVMdev Digest, Vol 80, Issue 13

[Andrew Clinton]

Agreed, I too was wondering why we need both arrays and vectors.  It 
goes against the grain, I think, of the structure typing system used by 
LLVM.  For example, a vector of 4 floats and an array of 4 floats are 
structurally the same type.  Would it be feasible in the future to 
consolidate the two types by allowing "vector" operations (add, 
multiply, etc.) on arrays where it makes sense, and doing away with the 
specialized vector types?

Andrew

On 02/14/2011 03:49 PM, Peter Lawrence wrote:
> Andrew,
>                  your response highlights a naming problem in LLVM,
> which is that  "array" and "vector"
> mean the same thing in normal computer language and compiler theory
> usage, so it is
> inconvenient and misleading within LLVM to give one a very specific
> meaning that is different
> from the other....
>
> to the LLVM developers I would suggest using the term "packed" to
> refer to the type of
> data that the SPARC-VIS, the PPC-Altivec, and the Intel-mmx/sse
> (among others) instruction
> sets support.
>
> As far as I am aware not a single one of any of the above types of
> instruction sets allows the "subscripting" of packed data within a
> register  (the Maspar
> computer had hardware that would allow subscripting of sub-elements
> of data within
> a larger/wider register, but it was the exception, not the rule, and
> it did not support
> any of the saturating arithmetic that is part-and-parcel of the
> packed data types in
> the currently existing "multi-media instruction sets").
>
>
> sincerely,
> Peter Lawrence.
>