[Dwarf-Discuss] modeling different address spaces

[Metzger, Markus T]

Hello Michael,

Sorry for the late reply.  I found the email in the spam folder today.

> >>> We'd also want an unbounded piece operator to describe partially
> registerized
> >>> unbounded arrays, but I have not worked that out in detail, yet, and we're a
> bit
> >>> farther away from an implementation.
> >>
> >> Can you describe this more?
> >
> > Consider a large array kept in memory and a for loop iterating over the array.
> If that
> > loop gets vectorized, compilers would load a portion of the array into registers
> at the
> > beginning of the loop body, operate on the registers, and write them back at
> the end
> > of the loop body.
> >
> > The entire array can be split into three pieces:
> > - elements that have already been processed: in memory
> > - elements that are currently being processed: in registers
> > - elements that will be processed in future iterations: in memory
> >
> > For unbounded arrays, the size of the third piece is not known.
> 
> When would you need to know the third piece?
> 
> How is this different from a non-vector processor doing an optimized
> string operation, loading 4 characters into a register at a time?  If
> the string is nul-terminated, the string length might be unknown.

I don't think that this is different from the use-case I sketched above.  We wouldn't
even need to load a sequence of elements.  Loading a single element would produce
the same scenario.

Can this be described in DWARF today?

Markus.

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