Re: [f-cpu] loadconsx and stream hints

[Yann Guidon <whygee@f-cpu.org>]

hi,

devik wrote:

> Please can someone explain me syntax and semantic
> of latest loadconsx (and loadcons.n) so I can add
> them to gcc ?
i prefer to stick with the old/original "loadcons[x]" which writes
a 16-bit constant to a given part of a register.

> Also if someone can write a few words what stream
> bits can be good for - I can't find definition. Will
> there be separate caches for each stream for example ?
>  
stream hints are used to differentiate unrelated data streams,
that is, flows (in and out) from memory from separate, independent
arrays.

By default there is no hint (hint #0) but this can be useful in future
architectures where multiple Load/Store Units are implemented
or when there is a direct SDRAM interface (the stream hint bit
can then serve as a bank number, in order to optimise prefetch
time and bandwidth).

It is not yet used and can remain zero, but i guess that the SDRAM bank 
trick
will be used first because it simplifies the SDRAM interface logic.
A "hint number" (or bank number, or transaction number)
can be allocated to the stack, the others are used for continuous 
(streaming)
access to main memory (for example, one is needed for memset and two are
needed for strcmp).

> thx, devik
YG

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