[avr-gcc-list] Re: C vs. assembly performance

[David Brown]

Georg-Johann Lay wrote:
> David Brown schrieb:
> > Georg-Johann Lay wrote:
> > > regardless if optimization is on or not. If fact I would guess that 
> > > it is a policy that the code *must* be the same regardless what debug 
> > > level (if any) or debug format is used, and code beeing dependent on 
> > > debug level/format is worth a bug report.
>
> uaaa, typo devil above. I meant "debugging info enabled" instead of 
> "optimization" in the first line. With "optimization" my statement is 
> obvious nonsense. blush.
>
> > That is certainly not true.  Enabling debug information will disable 
> > or limit some optimisations.  gcc in general is pretty good at optimising 
>
> Can you make that explicit with an example? With "code" I mean code that 
> will end up in the target, i.e. no code that lives in some .stab* or 
> .debug* section.
>
> But I must admit that I don't debug my code and consequently have debug 
> info turned off, so I am not familiar with debugging info and maybe 
> fundamentally wrong on gcc policies concerning that topic.
>
> Turned on -g3 for a try in my actual AVR project (12k .text) does not 
> show other sizes for .text, and static ram usage is exactly the same as 
> without -g3. Size of .i, .s, .o and .elf stuff will increase because of 
> debug info, but .text and .data et al. should not change, neither in 
> size, nor in content.

A few quick tests here confirm what you've said.  I looks like my 
understanding of debug data generation is a bit outdated.

mvh.,

David