[Bug tree-optimization/34683] SSA rewriting in the loop unroller causes quadratic behavior

["jaydub66 at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #45 from jaydub66 at gmail dot com  2008-01-10 20:14 -------
(In reply to comment #42)
> This is probably all we can get for now - maybe another few % with minor
> tweaks,
> but nothing earth-shattering.  After all, we _do_ have a much larger IL due
> to the number of VOPs not partitioned.

Well, it may not be earth-shattering, but it's still a solid improvement - of
more than a few %! With rev. 131446 I get the following numbers:

-O1 -fstrict-aliasing: 11sec, 201825 kB
-O2:                   22sec, 392166 kB
-O3:                   24sec, 388802 kB

Compile time is reduced by a factor of 4 for -O2, and memory usage is halved
for -O1! Nice job, Richard.

So I'd say compile time really isn't an issue any more. But memory consumption
is still a factor of 10 above what it was last year. Most of that comes from
'tree FRE' (~140MB), but all the junk in 'tree operand scan' is gone. For -O2
and -O3 another large chunk appears in 'tree PRE' (~160MB).

Are you sure you want to close this bug? For me memory consumption is still an
issue, and I would really like to see this fixed at some point. And if there is
another bug which is a duplicate of this, could you point me to it?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34683