On Wed, Apr 20, 2016 at 10:55:45 -0700, Richard Henderson wrote:
On 04/20/2016 10:17 AM, Emilio G. Cota wrote:
I've tried to find a GCC intrinsic for test-and-set, and I've only found
lock_test_and_set, which is what we use for atomic_xchg (except on ppc)
because it really is an atomic exchange:
"This builtin, as described by Intel, is not a traditional test-and-set
operation, but rather an atomic exchange operation."
https://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Atomic-Builtins.html
Please read the entire documentation, not just the first sentence.
I did read it and I'm aware of the limitations of using xchg.
My comment was related to this:
[...] do note that there are compiler primitives for test-and-set that
(can be) simpler for a cpu to implement than xchg.
What compiler (I assume gcc) primitives are these? I couldn't find them.