Re: [f-cpu] Always problem with SIMD and RC5

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

hi,

cedric wrote:
> > cedric wrote:
> > > I always have a problem with my final test in my RC5 algorithm. I don't
> > > find a way to know the number of chunk or the current max size of the
> > > SIMD registers. Perhaps did we need to add two new SR :
> > >   SR_REGISTER_SIZE_MAX = the maximum size of a register in SIMD mode
> > This already exists, it's SR_MAX_SIZE
> 
> > >   SR_REGISTER_CURRENT_SIZE = the current limit.
> > > (If thing that both a required, because we need to first know in wich
> > > state we are and then change the value arcoding to the CPU and the
> > > algorithm)
> 
> > if you want to do it "the hard way", take the maximum value
> > that you find in SR_SIZE_0 to SR_SIZE_3. But by convention, you can decide
> > to put the maximum size in SR_SIZE_3, which usually corresponds to size=64
> > bits when the CPU is limited to 64 bits.
> 
> > hope this old trick helps,
> Euh, ok, if you prefer, I want to know if SR_MAX_SIZE div SR_SIZE_Q = Number
> of chunk in a register ? I think yes, but I am not sure.

SR_MAX_SIZE and SR_SIZE_x are powers of two, in bytes. If you have 32-bit
chunks, you can write
 geti SR_MAX_SIZE, r1
 shri 2, r1, r1
and r1 contains the number of 32-bit words per register.

> A+
>   Cedric
WHYGEE
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