Re: Huge compile time & run time performance regression 3.3 -> HEAD

[Gabriel Dos Reis <gdr@integrable-solutions.net>]

Richard Guenther <rguenth@tat.physik.uni-tuebingen.de> writes:

| > Do you see any compile time regressions at -O0?
| >
| > (I'm asking for the obvious reason: trying to find out how much work we
| > need to do in the front end as opposed to the back end.)
| 
| After killing all forced inlining, I get almost the same timings from 3.3
| and 3.4, namely 42.50 and 44.89 seconds.
| 
| Slowdown comes from
| 
| 3.3: name lookup           :   6.92 (17%) usr   0.90 (43%) sys   7.50
| (18%) wall
| 3.4: name lookup           :   9.06 (22%) usr   0.81 (39%) sys  10.29
| (23%) wall

I've also noticed that name lookup time has increased from 3.3 to 3.4,
probably mostly because now we're doing things more correctly and
partly because we didn't really take care to optimize it.  It would be
interesting if you could report numbers for name lookup for 3.4:

  * before I applied the name lookup
  * after I applied it (i.e. cvs as of this moment)

What I've noted (and I posted figures) wkas that the patch I applied
cut the name lookup time about half on mainline, whereas I got at
least 20%  on branch.

Thanks,

-- Gaby