Re: optimization/10160: [3.3/3.4 regression][SPARC] compile time regression; inordinate time spent in "scheduling"

[Vladimir Makarov <vmakarov at redhat dot com>]

The following reply was made to PR optimization/10160; it has been noted by GNATS.

From: Vladimir Makarov <vmakarov at redhat dot com>
To: ebotcazou at gcc dot gnu dot org, china at thewrittenword dot com,
	gcc-bugs at gcc dot gnu dot org, gcc-prs at gcc dot gnu dot org, vmakarov at gcc dot gnu dot org,
	gcc-gnats at gcc dot gnu dot org
Cc:  
Subject: Re: optimization/10160: [3.3/3.4 regression][SPARC] compile time 
 regression; inordinate time spent in "scheduling"
Date: Wed, 16 Apr 2003 13:39:59 -0400

 ebotcazou at gcc dot gnu dot org wrote:
 > 
 > Synopsis: [3.3/3.4 regression][SPARC] compile time regression; inordinate time spent in "scheduling"
 > 
 > Responsible-Changed-From-To: vmakarov->ebotcazou
 > Responsible-Changed-By: ebotcazou
 > Responsible-Changed-When: Wed Apr 16 13:14:39 2003
 > Responsible-Changed-Why:
 >     Hum... I don't think that the scheduler is to be blamed here,
 >     rather the tree inliner: cutting the inlining limit by 10
 >     (-finline-limit=60) brings the compile time on par with that
 >     of the 3.2.x branch.
 > 
 >     The new logic of the tree inliner is not exactly adapted to this testcase.
 > 
 > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=10160
 
 You are absolutely right.  I was afraid that it is because of the first
 cycle multipass insn scheduling.  So I switched it off and got the same
 result.  So this is not because of the recent insn scheduling changes. 
 Simply insn scheduling (even simplest heuristic list one) is O(n*2)
 algorithm.  So it may behave very nasty when the input is big.  There
 are some heuristics constraining number of dependencies but they do not
 help in this case.  Even without insn scheduling compilation of this
 file takes 12 minutes on my sparc computer.
 
 Vlad