Atomic operations (increment, decrement, compare exchange?)

[Jeff Ward]

Hi Naclers!

Are there any built in atomic operations available for NaCL yet?  Things like win32's InterlockedIncrement, InterlocedDecrement, or InterlockedCompareExchange?

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Jeff

[Derek Schuff]

Hi Jeff,

It depends on what you mean by "built in." There are plenty of ways to get atomic operations, in various libraries (e.g. the examples you gave are in the win32 library), or built right into the compiler. Win32 is obviously not available in NaCl, but the gcc compiler has several builtin functions for atomic operations: http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Atomic-Builtins.html That set includes interlocked increment/decrement (either __sync_fetch_and_add or __sync_add_and_fetch can be used for atomic increment) and compare and swap, and a few others. 

-Derek

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Jeff

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[Victor Khimenko]

On Tue, Nov 29, 2011 at 10:07 AM, Derek Schuff <dsc...@google.com> wrote:

Hi Jeff,

It depends on what you mean by "built in." There are plenty of ways to get atomic operations, in various libraries (e.g. the examples you gave are in the win32 library), or built right into the compiler. Win32 is obviously not available in NaCl, but the gcc compiler has several builtin functions for atomic operations: http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Atomic-Builtins.html That set includes interlocked increment/decrement (either __sync_fetch_and_add or __sync_add_and_fetch can be used for atomic increment) and compare and swap, and a few others. 

Proper link is http://gcc.gnu.org/onlinedocs/gcc-4.4.3/gcc/Atomic-Builtins.html , but it only fixes problem with NAND operation...

[Jeff Ward]

Thanks guys, exactly what I needed.

And these work as expected in NaCL?

[Derek Schuff]

Yes, the atomic gcc builtins all work in NaCl