[fpc-devel] Request info on static single use

Jonas Maebe jonas.maebe at elis.ugent.be
Wed Nov 8 18:03:46 CET 2006

On 8 nov 2006, at 17:58, Bart van den Broek wrote:

> All links you gave me lead to SSA,

No. The first google hit is a wikipedia article about SSA, but  
contains a subsection about SSU.

> I have gathered quite some documents on the subject.
> I found one reference in an SSI document to SSU and it was  
> discredited as incomplete (no algorithms) and vague.
> I thought you found some info i didnt see yet.
> So i guess you are using SSA?

No, SSU. SSU simply means that you not only rename a variable when  
it's written, but also when it's read. I.e.,

x1 := y1
z1 := y1;

is changed into

x2 := y1
y2 := y1
z2 := y2
y3 := y2

This allows the register allocator to more often change which  
registers are spilled to memory and which are kept in registers  
(which is mainly useful if you have few registers available)


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