RFR: 8187227: Zero should use compiler built-ins for atomics on linux-m68k

[John Paul Adrian Glaubitz]

On 11/23/2017 03:15 PM, Andrew Haley wrote:
> Take care: it's not absolutely guaranteed that the GCC builtins are
> correct for HotSpot.  Don't change anything that isn't broken.

I have tested them, both for m68k and ARMv4T, and both work fine.

Also, looking at what gcc does for ARM:

> https://github.com/gcc-mirror/gcc/blob/1cb6c2eb3b8361d850be8e8270c597270a1a7967/libgcc/config/arm/linux-atomic.c#L27

and what OpenJDK does for ARM:

> http://hg.openjdk.java.net/jdk/hs/file/ab188c22d4b6/src/hotspot/os_cpu/linux_zero/atomic_linux_zero.hpp#l101

it seems both code is identical as both call the kernel helper
for cmpxchg from the VDSO.

Adrian

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