[fpc-devel] Request info on static single use

Vincent Snijders vsnijders at quicknet.nl
Wed Nov 8 20:13:03 CET 2006

Jonas Maebe schreef:
> On 8 nov 2006, at 17:46, Micha Nelissen wrote:
>> 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) ?
> Yes.
>> 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.

Will you be working on SSA and/or SSU with control blocks (e.g. using 
SSA in procedures where a for loop is used) before 2.2? Or will that be 
released only in a later version.

A synthetic example that will benefit is the CalculatePoint procedure of 


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