[Bug c++/13776] [tree-ssa] Many C++ compile-time regression in 3.5-tree-ssa 040120

["rguenth at tat dot physik dot uni-tuebingen dot de" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From rguenth at tat dot physik dot uni-tuebingen dot de  2004-03-13 11:43 -------
Subject: Re:  [tree-ssa] Many C++ compile-time regression in
 3.5-tree-ssa 040120

dberlin at gcc dot gnu dot org wrote:
> ------- Additional Comments From dberlin at gcc dot gnu dot org  2004-03-13 02:10 -------
> (In reply to comment #14)
> 
>>Subject: Re:  [tree-ssa] Many C++ compile-time regression in
>>        3.5-tree-ssa 040120
>>
>>On Fri, 2004-03-12 at 21:02, dberlin at dberlin dot org wrote:
>>
>>
>>>I can't fix the algorithmic properties of the SSAPRE algorithm we use, 
>>>which is what you are running into, i'm betting.
>>>
>>
>>Could we add thresholds to back away from overly complicated functions?
>>
>>
>>Diego.
>>
>>
> 
> 
> 
> I need to know what exactly the properties of these functions are, it's unclear.
> As i said, i'm working on it.

Remember you need to patch the compiler to support 
__attribute__((leafify)) to trigger the problem with the tramp3d-v2.cpp 
testcase.  I suspect the huge number of basic blocks comes from inlining 
as I suspect at least one new basic block is inserted per inlined 
function, no?  So with a lot of C++ abstraction inside a leafified 
function you get a lot of basic blocks.  But I suppose a lot of them 
could be eliminated easily?

Richard.



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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13776