[PATCH] D71726: Let clang atomic builtins fetch add/sub support floating point types

[JF Bastien via Phabricator via cfe-commits]

jfb added a comment.

In D71726#2165445 <https://reviews.llvm.org/D71726#2165445>, @yaxunl wrote:

> In D71726#2165424 <https://reviews.llvm.org/D71726#2165424>, @jyknight wrote:
>
> > Why not have clang always emit atomicrmw for floats, and let AtomicExpandPass handle legalizing that into integer atomics if necessary, rather than adding a target hook in clang?
>
>
> Not all targets can legalize fp atomics by AtomicExpandPass. Some targets need library support.


What are they missing? It can be expanded to a cmpxchg loop with bitcast to an integer type of the same size.


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