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

[Jeff Law]

On 11/19/09 13:06, Linus Torvalds wrote:
> On Thu, 19 Nov 2009, H. Peter Anvin wrote:
>    
> > 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...
> >      
> As far as I know, that's true of _mcount already: it's not a normal ABI
> and is rather a highly architecture-specific special case to begin with.
> At least ARM has some (several?) special mcount calling conventions,
> afaik.
>    
Correct.  _mcount's ABI typically has been defined by the implementation 
of the vendor's C library mcount.

GCC has options to emit the profiling code prior to or after the 
prologue controllable through the usual variety of target macros & 
hooks.  I can't imagine anyone would object to a clean, tested patch to 
change how x86-linux's profiling code was implemented.

jeff



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