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Re: Optimizer suggestions for 4.x
- From: Andrew Pinski <pinskia at physics dot uc dot edu>
- To: "Sam Lauber" <sam124 at operamail dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Sun, 31 Oct 2004 15:55:53 -0500
- Subject: Re: Optimizer suggestions for 4.x
- References: <20041031204937.ECACE23C12@ws5-3.us4.outblaze.com>
On Oct 31, 2004, at 3:49 PM, Sam Lauber wrote:
According to the Info manuals for GCC (at least 3.3.3), the -fssa
option is buggy and not ready for production use. I think a
progressive optimizing solution would not only make ssa less buggy,
but if it was applied to the rest of cc1, it could up the amount of
optimization. I also think optimizatons should run in parrell so that
for example, when -O1 is specified, it will run two -O1/2s
(multithreading?). This would make optimization faster, especially
considering almost all programs nowadays are compiled with something
like "gcc -g -O2" or even -O3. Also, I think an -foptimize-loops
option should be added to convert loops that are appropriate to for
loops. I think also that specifying -Oanything should remove GOTOs
since they are messy and slow programming pratcice and can send the PC
bouncing like a Ping-Pong ball.
-fssa is removed from 3.4.0 and above. But now we have a tree level SSA
optimization which is turned on by default.
Also in 3.4.0, we already have the RTL based loop optimizations to
use CFG based instead of based notes. In 4.0.0, we have tree SSA
based loop optimizations already.
Also gotos are removed/changed so that they are not there are at all.
This has been done for a while, since at least 2.95, most likely a
large time before that.
Thanks,
Andrew Pinski