CODEWITHSUNDEEP
gccatomic
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mmmmmmmm

Reputation: 15513

GCC atomic built-ins: Is there a list showing which are supported on which platform?

Is there a site listing the various platforms and their support for GCC's atomic built-ins, for the various GCC versions?

EDIT:

To be more clear: GCC adds _sync... as intrinsics on platforms it contains support for. On all other platforms it keeps those as normal functions declarations but does not supply an implementation. This must be done by some framework.

So the question is: For which platforms does GCC supply which intrinsics without need to add a function implementation?

Upvotes: 4

Views: 3080

Answers (2)

kavadias
kavadias

Reputation: 1142

[Though this is an old question, I thought I should update and complete the answer]

I am not aware of a per-architecture-version and per-gcc-version table, describing supported built-ins.

The __sync built-in functions of gcc exist since version 4.1 (see, e.g., gcc 4.1.2 manual. As stated there:

Not all operations are supported by all target processors. If a particular operation cannot be implemented on the target processor, a warning will be generated and a call an external function will be generated. The external function will carry the same name as the builtin, with an additional suffix `_n' where n is the size of the data type.

So, when there is not an implementation for a specific architecture, a compilation warning will appear and, I guess, a link-time error, unless you provide the required function with the appropriate name.

After gcc 4.7 there are also __atomic built-ins and __sync built-ins are deprecated. For example, see how Fedora uses gcc __sync and __atomic here

Upvotes: 3

chill
chill

Reputation: 16888

I'm not aware if there's such a list, however http://gcc.gnu.org/projects/cxx0x.html says atomics are supported since GCC 4.4.

GCC libstdc++ implements <atomic> on top of the builtin functions `__sync_fetch_and_add' and friends ( http://gcc.gnu.org/onlinedocs/gcc-4.6.1/gcc/Atomic-Builtins.html ).

These functions are expanded either using machine specific expanders in the machine description of the target (usually in a file named `sync.md') or, lacking such expanders, using a CAS loop. If the presense of `sync.md' file is any indication for a proper atomics support, then you can count in MIPS, i386, ARM, BlackFin, Alpha, PowerPC, IA64 and Sparc.

Upvotes: 3

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