[ARM64] assert fail with 128-bit atomic: unimplemented reg-to-reg copy

[llvmbot]

Bugzilla Link	40693
Resolution	FIXED
Resolved on	Feb 12, 2019 02:46
Version	8.0
OS	Linux
Blocks	#39678
Reporter	LLVM Bugzilla Contributor
CC	@efriedma-quic,@zmodem,@zygoloid,@TNorthover

Extended Description

Fails on 8.0.0-rc2 at -O1 or higher (-O0 is ok).

clang -O2 --target=aarch64-linux-gnu -march=armv8.1a

void inc128(__int128 *p)
{
__int128 n, nn;
do {
__atomic_load(p, &n, __ATOMIC_RELAXED);
n = n + 1;
} while (!__sync_bool_compare_and_swap(p, n, nn));
}

[efriedma-quic]

There were a couple recent fixes here: r353308, r353383. We might want to cherry-pick to 8.0.

[zmodem]

Merged those in r353822.