Fwd: GCC Optimization for expressions

[Vincent Lefevre]

On 2008-12-01 13:02:21 -0800, Ian Lance Taylor wrote:
> "Nirav Shah" <nirav4ever4u@gmail.com> writes:
> 
> > No expression is evaluated in loop nor any particular intermediate
> > result is used more than once. Given this, can I get benefit in terms
> > of lesser clock cycle to execute the computation if done in a single
> > statement as compared to done over multiple statements with local
> > variables?
> 
> No.  When optimizing, the compiler converts your program into an
> internal representation in SSA form.  The number of local variables
> used in the original program is irrelevant to the generated code.

This may be what GCC currently does, but this is a bug when extended
precision is used to evaluate an expression.

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=323

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Vincent Lefèvre <vincent@vinc17.org> - Web: <http://www.vinc17.org/>
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