Compilation time in gcc-4.4.0

[Paolo Bonzini]

On 07/13/2010 04:53 PM, Richard Guenther wrote:
> On Tue, Jul 13, 2010 at 4:50 PM, Paolo Bonzini<bonzini@gnu.org>  wrote:
>> On 07/08/2010 10:58 PM, Maxiwell Garcia wrote:
>>>
>>> Hi,
>>>
>>> I am writing a paper about instruction-set architecture simulators. In
>>> first time, I used gcc-4.4.0 and the compilation time reached 33
>>> minutes (with -O3) for my simulator and the performance reached 270
>>> MIPS (Million instruction per second). When I used the gcc-4.4.4, in
>>> the same code, the compilation time reached 39 seconds and the
>>> performance reached 600 MIPS. My code have many "switchs" with 512
>>> "cases" and the library<systemc.h>    is in use.
>>> How to explain this behavior in the compilation and performance in my
>>> paper?
>>
>> Try -ftime-report, it should explain the compilation time change.  Such a
>> dramatic performance change is usually due to better register allocation,
>> but this is just a guess.
>
> I would guess it was the various backports of tree PRE fixes actually.

Sorry, I was referring to the change in performance which I justified by 
better register allocation.  PRE is indeed a good candidate for the 
compilation time fixes.  Could the changes to PRE cause different code 
to be generated?

Paolo