Re: c++/5504: Optimization breaks wei-ku-1 from blitz

[rth@gcc.gnu.org]

Synopsis: Optimization breaks wei-ku-1 from blitz

Responsible-Changed-From-To: jason->rth
Responsible-Changed-By: rth
Responsible-Changed-When: Wed Apr 10 10:42:22 2002
Responsible-Changed-Why:
    My patch.
State-Changed-From-To: analyzed->suspended
State-Changed-By: rth
State-Changed-When: Wed Apr 10 10:42:22 2002
State-Changed-Why:
    http://gcc.gnu.org/ml/gcc-patches/2002-04/msg00474.html
    
    Given enough memory, this solves the compile-time problem.
    It now takes about 6 minutes to compile instead of 7 hours.
    
    Peak memory usage is still atrocious though -- abour 1.2GB;
    I'm not sure how to solve that, or indeed if it can be solved.
    EH semantics of goto requires that all of the EH regions be
    created so that we can bind vs other EH regions at the end.
    Even if we discover in the middle that there will be no such
    goto requiring such processing, we'll have already created
    the rtl, which means that the memory is already in use.
    Since we can't garbage collect in the middle of rtl generation, 
    peak memory usage will not be impacted by any complex schemes
    in the middle of code generation.
    
    It may be possible to perform an optimization pass in which
    EH cleanups are removed from the AST before instantiation
    in rtl.  That would indeed positively impact peak memory use.
    Put that in the indefinite future though...

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=5504