C++ code generation: any way of deflating large expressions?

[Richard B. Kreckel]

Dear Hugo,

On Thu, 10 Jul 2003 hugo_lec at club-internet.fr wrote:
[...]
>        There's an algorithm to use the less temporary variables as possible (in order
> to help the compiler to optimize).
[...]

Could you please elaborate a little bit on that statement?

As it stands I find it slightly irritiating.  Is this assessment based on
real experience?  Given a compiler that transforms its parsed tree into
SSA form at some stage (as GCC 3.5 will), besides those phi-expressions
tons of temporaries are generated anyway in the IR.  More or less by
definition, later optimizations must cope with and reduce them.  So: is
there a point in trying to keep the number of temporaries low or is that
just fiction?

Maybe an example of the effect you are alluding at would be helpful.

Cheers
   -richy.
-- 
Richard B. Kreckel
<Richard.Kreckel at GiNaC.DE>
<http://www.ginac.de/~kreckel/>