ARM: support tlscall relocations

This adds support for TLS CALL relocations.  TLS CALL relocations are used to
indicate to the linker to generate appropriate entries to resolve TLS references
via an appropriate function invocation (e.g. __tls_get_addr(PLT)).

In order to accomodate the linker relaxation of the TLS access model for the
references (GD/LD -> IE, IE -> LE), the relocation addend must be incomplete.
This requires that the partial inplace value is also incomplete (i.e. 0).  We
simply avoid the offset value calculation at the time of the fixup adjustment in
the ARM assembler backend.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200446 91177308-0d34-0410-b5e6-96231b3b80d8
ARM: support TLS descriptor relocations

Add support for tlsdesc relocations which are part of the ABI, marked as
experimental.  These relocations permit the linker to perform TLS reference
optimizations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200447 91177308-0d34-0410-b5e6-96231b3b80d8
ARM: suuport .tlsdescseq directive

This enhances the ARMAsmParser to handle .tlsdescseq directives.  This is a
slightly special relocation.  We must be able to generate them, but not consume
them in assembly.  The relocation is meant to assist the linker in generating a
TLS descriptor sequence.  The ELF target streamer is enhanced to append
additional fixups into the current segment and that is used to emit the new
R_ARM_TLS_DESCSEQ relocations.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200448 91177308-0d34-0410-b5e6-96231b3b80d8
ARM IAS: support .movsp

.movsp is an ARM unwinding directive that indicates to the unwinder that a
register contains an offset from the current stack pointer.  If the offset is
unspecified, it defaults to zero.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200449 91177308-0d34-0410-b5e6-96231b3b80d8
tools: add support for decoding ARM attributes

Enhance the ARM specific parsing support in llvm-readobj to support attributes.
This allows for simpler tests to validate encoding of the build attributes as
specified in the ARM ELF specification.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200450 91177308-0d34-0410-b5e6-96231b3b80d8
ARM IAS: support .object_arch

The .object_arch directive indicates an alternative architecture to be specified
in the object file.  The directive does *not* effect the enabled feature bits
for the object file generation.  This is particularly useful when the code
performs runtime detection and would like to indicate a lower architecture as
the requirements than the actual instructions used.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200451 91177308-0d34-0410-b5e6-96231b3b80d8
Implement SPARCv9 atomic_swap_64 with a pseudo.

The SWAP instruction only exists in a 32-bit variant, but the 64-bit
atomic swap can be implemented in terms of CASX, like the other atomic
rmw primitives.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@200453 91177308-0d34-0410-b5e6-96231b3b80d8