Re: [avr-gcc-list] Avr-gcc Produces Incorrect Code with -Os

[David Brown]

Andy H wrote:
> http://gcc.gnu.org/onlinedocs/gcc-4.1.0/gcc/Atomic-Builtins.html

To quote from the first paragraph of that manual page:

The following builtins are intended to be compatible with those 
described in the Intel Itanium Processor-specific Application Binary 
Interface, section 7.4. As such, they depart from the normal GCC 
practice of using the “__builtin_” prefix, and further that they are 
overloaded such that they work on multiple types.


I've never used these functions, so I may be skating on thin ice here - 
you'll no doubt correct me if I'm wrong!

These "atomic access" builtins are very much specific to the Itanium - 
they are basically wrappers around some assembly primitives, for use in 
operating system fundamentals such as locks and synchronisation 
primitives.  For other targets, people normally just use a couple of 
lines of inline assembly - for the Itanium, assembly language is so 
hideous that it's worth having these builtin wrappers.


While I think it is worth having a set of consistent atomic access 
builtins that work across gcc ports, I'm not sure the Itanium's 
functions are the best model.

mvh.,

David