Proposed

Name	Opcodes	Size
is_lock_free	0xff00	1
wake	0xff01	1
i32.wait	0xff02	1
i64.wait	0xff03	1
available	0xff04..0xff0f	12
*.atomic.rmw*.*	0xff10..0xff1b	12
*.atomic.rmw*.cmpxchg*	0xff1c..0xff27	12
*.atomic.load*	0xff28..0xff35	14
*.atomic.store*	0xff36..0xff3e	9
available	0xff3f..0xffff	193

As a cute feature, the opcodes for atomic load/store match the opcodes for load/store.

Factoring out RMW ops

Name	Opcodes	Size
is_lock_free	0xff00	1
wake	0xff01	1
i32.wait	0xff02	1
i64.wait	0xff03	1
available	0xff04..0xff0f	12
*.atomic.rmw*.add	0xff10..0xff1b	12
*.atomic.rmw*.cmpxchg*	0xff1c..0xff27	12
*.atomic.load*	0xff28..0xff35	14
*.atomic.store*	0xff36..0xff3e	9
*.atomic.rmw*.sub	0xff3f..0xff4a	12
*.atomic.rmw*.and	0xff4b..0xff56	12
*.atomic.rmw*.or	0xff57..0xff62	12
*.atomic.rmw*.xor	0xff63..0xff6e	12
*.atomic.rmw*.xchg	0xff6f..0xff7a	12
available	0xff7b..0xffff	133