Re: Early inlining

[Jan Hubicka <hubicka at ucw dot cz>]

> 
> On Jun 23, 2005, at 7:37 PM, Jan Hubicka wrote:
> 
> >Hi,
> >this patch adds early inlining.  As discussed earlier it helps
> >noticeably to cut down expenses of tree profiling on testcases with
> >extreme function call overhead (such as tramp3d).  It also save memory
> >on Gerald's testcase and makes GCC module compilation test apparently
> >tinny bit faster at -O3 (but close to noise).  In the future I would
> >like to have more optimizations in between the early inlining and real
> >inliing that will make this infrastructure bit more usefull, but at
> >the moment it seems to solve some side cases and have no measurable
> >overhead otherwise (even tought we rebuild cgraph edges after the  
> >early
> >passes) so I am enabling it by default now.
> ...
> 
> Jan -
> 
> After this patch, I see that static functions called once that are  
> inlined are no longer removed from the CFG during actual (not early)  
> inlining.  Assuming this is the intended behavior, there is a slight  

Well, this is not quite intended - the actual inlining behaviour should
not be affected by the patch.  I will take a look into this...

Honza
> issue that is raised in the function cgraph_decide_inlining().  This  
> can be seen by compiling the attached test.c with "-O3 -fdump-ipa- 
> all", producing a sefault.  The problem is that when inlining  
> functions called once (starting around ipa-inline.c:809), we call  
> cgraph_mark_inline() which creates a duplicate callee node, resetting  
> node->callers to NULL.  With dumps enabled, this causes a null- 
> pointer reference immediately after.  The attached patch addresses  
> the issue by holding on to the edge across the call to  
> cgraph_mark_inline.  I haven't run any regression tests on this yet,  
> but I wanted to be sure that the original behavior of no longer  
> removing CFG nodes was the intended behavior first.
> 
> Shall I kick off the tests?
> 
> - Josh
> ~~~~~~
> Josh Conner
>