Re: [RFC] Contributing tree-ssa to mainline

[Andrew Pinski <pinskia@physics.uc.edu>]

On Jan 16, 2004, at 21:52, Per Bothner wrote:

> Diego Novillo wrote:
>
>> On Fri, 2004-01-16 at 22:24, Richard Kenner wrote:
>>> Remember that the last time we had the discussion of the timing of 
>>> tree-ssa,
>>> people claimed it was "essential" for 3.5 since there was a 
>>> tremendous
>>> improvement on some C++ cases.  So let's see those cases.
>>>
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12747
>
> Can you give numbers?  I.e. how much faster does that (or a similar)
> testcase run?  Have we met Kenner's 2x goal?

First it also improves C code also.
See PR 9540 for an example
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=9540

And PR 2806 for an example where the if combiner on the tree-ssa
beats the heck out of the one on the RTL level.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=2806

Also PR 9566 where the problem is that GCC will put things on the stack 
too early.
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=9566

These can be any were between .5x and 10x depending on how big the 
struct is and if you
have large number of copies.

Also compile time for some testcases are much better, see PR 2692 for 
an example:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=2692

Also the stack sizes that most function needs is going be lowered by a 
significant amount in
most C++ cases.  There are many test cases in the bugzilla for this.

I think the tree-ssa is in good shape to be included in for 3.5 except 
for the current
problem of bootstrapping on some targets/building for some targets, 
these really should be
fixed before the merging should happen.

Thanks,
Andrew Pinski