[LLVMdev] ARM/MC/ELF Support for pcrel movw/movt coming soon

[Jason Kim]

Hi everyone, happy new year.

This note is to announce that support for PC relative reloc tags for
movw/movt is nearing completion (hopefully <48hrs!). This work is is
from Jan Voung, David Meyer and myself.

Unfortunately, to test this change, we need to patch ARM/AsmParser to
address http://llvm.org/bugs/show_bug.cgi?id=8721
Locally, we have hacked up a solution to 8721, but its not ideal since
VK_ARM_HI16 and VK_ARM_LO16 should apply to any MCExpr, not just
MCSymbolRef like it is now.
The proper fix to 8721 looks to be nontrivial, so what I will do is
commit the "hack" patch to 8721 separately, and then the main patch,
as 8721 is blocking the testing.
The interim hack for 8721 can then be rolled back separately once
someone (ddunbar? pdox? me? :) get around to refactoring MCExpr so
that :lower16: and :upper16: can apply to arbitrary expressions.

Thanks
-jason