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Subject: [Bug c++/55135] Segfault of gcc on a big file
Date: Thu, 28 Feb 2013 23:59:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55135

--- Comment #10 from Steven Bosscher <steven at gcc dot gnu.org> 2013-02-28 23:58:38 UTC ---
Created attachment 29557
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29557
Collected hacks to make the test case compile in reasonable time with -O0

Patch does 2 things:

- Queue up to-be-removed EH regions, instead of removing them one-by-one.
  Removing them one at a time results in walking the list of EH regions
  repeatedly, thus taking O(# of EH regions ** 2) time.

- Rewrite init_subregs_of_mode and subroutines to first collect the
  invalid mode change subregs in sbitmaps, and then converting the final
  sbitmap to a bitmap. This trades memory for time: the bitmap lookups are
  also potentially O(# of registers ** 2) and this test case has more than
  one million registers, many of them with invalid mode changes (to be fixed
  up by IRA/LRA).

Peak memory at -O0 is <4GB. Compile time on a "Quad-Core AMD Opteron(tm)
Processor 8354" at 2200MHz is 240s, half of it still taken up by IRA+LRA.

At -O1 the einline pass is consuming almost all compile time again.
-> Honza: Can we please have a proper permanent fix for this recurring
problem? What's there now just Does Not Work!