[mercury-users] Field assignment optimisation

[Julien Fischer]

On Mon, 9 May 2005, Michael Day wrote:

> > Can you send us your test program?  What optimization level are you
> > using?  These intermediate structures certainly *should* be optimized
> > away.
>
> I'm only guessing at what is going on, but based on timing and mprof
> output replacing the multiple field assignments with a single construction
> gives quite a significant speedup.
>
> The structure in question has 87 fields and there were 12 field
> assignments.
>
> The compilation grade is asm_fast.gc (and asm_fast.gc.prof) and the
> compilation options include -O5 --intermodule-optimisation
> --trans-intermod-opt.
>
> Providing the entire program is not possible in this case however, as it
> is rather large.
>

No matter, we've just provided our own test program ;-).  You're correct,
the compiler is doing a really dreadful job of optimizing multiple
field assignments (essentially by not optimizing them at all.)

Cheers,
Julien.
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