[fpc-devel] Request info on static single use

Jonas Maebe jonas.maebe at elis.ugent.be
Wed Nov 8 18:01:00 CET 2006

On 8 nov 2006, at 17:46, Micha Nelissen wrote:

> Jonas Maebe wrote:
>> On 8 nov 2006, at 17:11, Bart van den Broek wrote:
>>> Can someone give me a reference to static single use (for example  
>>> scientific paper).
>>> I know SSA and SSI (I = information).
>> http://www.google.com/search?q=static+single+use
> Is SSU easier to implement than SSA ?

No, it's a bit more work.

> Aren't variables often more used than assigned (so more generated  
> variables by SSU) ?


> How do the achieved optimizations compare ?

SSU gives somewhat better results on register-starved architectures.  
The change from SSA to SSU didn't make any difference for PPC for the  
compiler+rtl (it can give a difference for large procedures with a  
lot of variables which are used in different "phases" of course). It  
saves about 5kb on the compiler on Linux/i386 compared to SSA-only.


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