Richard Sandiford bef3d7af2b Add TargetLowering::prepareVolatileOrAtomicLoad ...

One unusual feature of the z architecture is that the result of a
previous load can be reused indefinitely for subsequent loads, even if
a cache-coherent store to that location is performed by another CPU.
A special serializing instruction must be used if you want to force
a load to be reattempted.

Since volatile loads are not supposed to be omitted in this way,
we should insert a serializing instruction before each such load.
The same goes for atomic loads.

The patch implements this at the IR->DAG boundary, in a similar way
to atomic fences.  It is a no-op for targets other than SystemZ.

llvm-svn: 196906

2013-12-10 10:49:34 +00:00

263 B

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