RFE: CCS support for PPC64/Linux

[Paul Hargrove]

The ABI for PPC64 (big-endian) on Linux is unusual in such a way that our new support for Cross Code Segment (CCC) RPC cannot currently map function pointers (which are not addresses in a code segment) to linker segments.

The information that would probably allow us to add support can be found here: https://community.ibm.com/community/user/power/blogs/archive-user/2013/08/01/deeply-understand-64-bit-powerpc-elf-abi-function-descriptors

[Paul Hargrove]

@Colin MacLean

Not to "fix" this bug, but to improve the failure behavior, would you consider add "ban list" logic to trigger the #error "CCS not supported ..." message when this ABI is detected? If so, I can provide the right preprocessor tokens to perform the identification.

[Paul Hargrove]

Since gasnet_macros.sh already checks ARCH_POWERPC, one should be able to simply add ARCH_BIG_ENDIAN to the identifier list in that file. Once that is done, (UPCXXI_PLATFORM_ARCH_POWERPC && UPCXXI_PLATFORM_ARCH_BIG_ENDIAN) should reliably identify this platform.

[Dan Bonachea]

Requested error added in pull request #416 merged at 61336f1

Enhancement request remains open for possible later addition (unlikely unless some stakeholder expresses interest)