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Re: Flatten sysdeps/unix/bsd/bsd4.4 into sysdeps/unix/bsd


From: "Joseph S. Myers" <joseph@codesourcery.com>
Date: Thu, 17 May 2012 23:26:37 +0000 (UTC)

> On Thu, 17 May 2012, David Miller wrote:
> 
>> Not to mention the well understood extreme computational complexity
>> this scheme has in the context of make due to the amount of prefix
>> rules that get made to support this.
> 
> I have the idea that you could reduce the number of rules rather a lot by 
> arranging for sysd-rules to contain rules only where the sysdeps directory 
> in question contains at least one file with the given suffix.  I don't 
> know how much that would help (but, for example, rules using .s sources as 
> opposed to .S are useless for every architecture other than alpha and 
> hppa) or whether that reduction translates into less time spent in "make", 
> but it seems at least plausible that it would give a useful build speedup 
> until we have any more general solution.

That would eliminate around 1/4 of the prefix rules I believe.

Actually, my initial impression for this case is to simply rename the
hppa/alpha foo.s files to foo.S and then remove the prefix rule case
for .s entirely.

Is there something fundamental blocking that sort of change?

Another observation for shorter-term fixes is that we could, early in
the build, determine cases where we'll never end up using any of the
files in a sysdep directory because an earlier sysdep dir always has a
candidate.


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