[RFR]: 8186461: zero: Don't use PowerPC FPU instructions on targets without FPU

[John Paul Adrian Glaubitz]

For 32-Bit PowerPC, zero contains a platform-specific implementation of
atomic_copy64() which uses inline-assembly with FPU instructions to
perform a 64-bit atomic copy.

Unfortunately, the inline assembly with the FPU instructions is
unconditionally enabled on all 32-Bit PowerPC machines which means that
the code in question will fail to build on 32-Bit PowerPC machines without
an FPU.

On such systems are for example the PowerPC e500 CPU, gcc will define
the macro __NO_FPRS__:

root at atlantis:~> echo | gcc -E -dM - |grep -i FPR
#define __NO_FPRS__ 1
root at atlantis:~>

Thus, in order to make sure zero builds on these systems without problems,
we should not just test whether PPC32 is defined but also that __NO_FPRS__
is not defined before enabling the inline assembly with FPU instructions.

Bug is described in [1] with an attached patch.

Adrian

> [1] https://bugs.openjdk.java.net/browse/JDK-8186461

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 .''`.  John Paul Adrian Glaubitz
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