[m-rev.] for review: fix equivalence type performance problems

[Fergus Henderson]

On 18-Dec-2003, Simon Taylor <stayl at cs.mu.OZ.AU> wrote:
> On 18-Dec-2003, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> > On 17-Dec-2003, Simon Taylor <stayl at cs.mu.OZ.AU> wrote:
> > > On 12-Dec-2003, Fergus Henderson <fjh at cs.mu.OZ.AU> wrote:
> > > > On 12-Dec-2003, Simon Taylor <stayl at cs.mu.OZ.AU> wrote:
> > > > > compiler/mercury_compile.m:
> > > > > 	Re-enable equiv_type_hlds.m.
> > > > > 
> > > > > tests/hard_coded/Mmakefile:
> > > > > 	Re-enable testing of equiv_type_hlds.m.
> > > > 
> > > > I would like to see some performance figures for how much
> > > > it costs to run this extra pass before we re-enable it.
> > > 
> > > With the extra change below, the equiv_type_hlds pass adds about
> > > 5% to compile time, much of that in equiv_type.replace_in_type.
> > 
> > The extra changes below are fine.
> > 
> > I'd still rather avoid the extra 5% if we can...
> > for the --high-level-data grades we can't, but is this pass
> > really needed for the hlc and LLDS grades?
> 
> I'd say yes, because otherwise `:- pragma foreign_proc' and
> `:- pragma export' will behave differently in different grades;
> the foreign types of the arguments will be different.

Could we just expand equivalence types when converting Mercury types
to foreign types?  In particular, in foreign__to_exported_type?

We're already looking up the HLDS type definition there, to check for
`foreign_type' declarations, so it wouldn't cost much more to check for
equivalence types and expand them too.  I think that should cost a lot
less than 5%.

-- 
Fergus Henderson <fjh at cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.
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