[PATCH] D45321: [atomics] Fix runtime calls for misaligned atomics

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


================
Comment at: compiler-rt/lib/builtins/atomic.c:158
         /* FIXME: __uint128_t isn't available on 32 bit platforms.
         LOCK_FREE_ACTION(__uint128_t);*/\
       }\
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t.p.northover wrote:
> efriedma wrote:
> > We also need to fix this FIXME, for correctness... if we have a 16-byte atomic store implementation, we need to use it.
> Any chance I could skip that for now?
> 
> It's an order of magnitude harder than fixing the misalignment problems since LLVM already generates a mixture of libcalls and cmpxchg based on the CPU for x86, which forces this to be a runtime CPUID check.
> 
> 
> 
> 
Can you at least fix it for targets where 16-byte atomics are always lock-free, like aarch64?  (Of course I don't expect you to implement the x86 cpuid bits.)


Repository:
  rCRT Compiler Runtime

https://reviews.llvm.org/D45321