Re: BUG: GCC-4.4.x changes the function frame on some functions

[Steven Rostedt]

On Thu, 2009-11-19 at 11:50 -0800, H. Peter Anvin wrote:

> > Perhaps we could create another profiler? Instead of calling mcount,
> > call a new function: __fentry__ or something. Have it activated with
> > another switch. This could make the performance of the function tracer
> > even better without all these exceptions.
> > 
> > 	<function>:
> > 		call __fentry__
> > 		[...]
> > 
> 
> Calling the profiler immediately at the entry point is clearly the more
> sane option.  It means the ABI is well-defined, stable, and independent
> of what the actual function contents are.  It means that ABI isn't the
> normal C ABI (the __fentry__ function would have to preserve all
> registers), but that's fine...

mcount already has that requirement (saving all/most regs). Anyway, you
are right, we don't care. The tracer should carry the blunt of the load,
not the individual callers.

-- Steve


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