openjdk/zero: use double code for atomic64 on powerpc (original) (raw)

Gary Benson gbenson at redhat.com
Wed Jun 30 09:10:51 PDT 2010

Andrew Haley wrote:

On 06/30/2010 04:30 PM, Sebastian Andrzej Siewior wrote: > this cute C code does the same thing on powerpc as the assembly > code that was here before. If the compiler was built with the SPE > extensions instead of traditional FPU and double operations are > performed in HW then we are one step further: The compiler turns > this into evldd & evstdd. Voila :) > > This C code could also be activated on s390. The compiler turns > this into a single mvc instruction which does the copy > operation. I don't know if mvc's copy ability is atomic or not > and therefore I leave it as it.

I don't quite understand this. Is it guaranteed that double stores on ppc are atomic?

No, but it does seem to work. The same trick is used in the kernel to write to flash drives IIRC.

Cheers, Gary

-- http://gbenson.net/

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