Re: [avr-gcc-list] Re: AVR byte swap optimization

[Shaun Jackman]

On 12/18/06, David VanHorn <address@hidden> wrote:
> Am I missing something here?
> Why not pop to assembler, push the high, push the low, pop the high, pop the
> low?

* Inline assembler cannot be used at compile time, for example to
initialize a static variable.

* If the swap function is called on a constant, the compiler cannot
remove the inline assembler. In general, any inline assembler tends to
handcuff the optimizer to some degree.

* Push and pop take two cycles since they access memory. Three mov
instructions are faster than one push and one pop.

Cheers,
Shaun