Craig Topper 8d46403b8e [X86] Add CMPXCHG8B feature flag. Set it for all CPUs except i386/i486 including 'generic'. Disable use of CMPXCHG8B when this flag isn't set. ...

CMPXCHG8B was introduced on i586/pentium generation.

If its not enabled, limit the atomic width to 32 bits so the AtomicExpandPass will expand to lib calls. Unclear if we should be using a different limit for other configs. The default is 1024 and experimentation shows that using an i256 atomic will cause a crash in SelectionDAG.

Differential Revision: https://reviews.llvm.org/D59576

llvm-svn: 356631

2019-03-20 23:35:49 +00:00

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