It should be possible provide implementations of the following section of gcc.h in terms of C11 intrinsics given a sufficiently new version of GCC:

https://github.com/wiredtiger/wiredtiger/blob/be18e7cf192c5ef7a6b782370a3765a0883a5186/src/include/gcc.h#L155-L236

Doing so would make the code more portable. In particular, we would like to be able to target both -march=z9-109 -mtune=z10 and -march=z196 -mtune=zEC12 in MongoDB 3.4, which have different barrier instructions, but there is no preprocessor define which distinguishes these settings.

We would need to find the appropriate incantation for each of

• WT_PAUSE
• WT_BARRIER
• WT_WRITE_BARRIER
• WT_READ_BARRIER
• WT_FULL_BARRIER

The following table contains a proposed mapping from the x86 primitives to the C11 equivalent.

__asm__ volatile("" ::: "memory")

atomic_signal_fence(memory_order_acq_rel)

__asm__ volatile ("lfence" ::: "memory"

atomic_thread_fence(memory_order_acquire)

__asm__ volatile ("sfence" ::: "memory"

atomic_thread_fence(memory_order_release)

__asm__ volatile ("mfence" ::: "memory")

atomic_thread_fence(memory_order_acq_rel)

These seem to be the only options, in terms of API calls, because all of the other C11 atomic operations act on specific memory addresses - only atomic_signal_fence and atomic_thread_fence do not.