Trivial cleanup: reuse existing variable.

Extracted while trying to understand http://llvm-reviews.chandlerc.com/D1764.

Patch by Matt Arsenault.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201425 91177308-0d34-0410-b5e6-96231b3b80d8
This patch has two main functions:

1) Fix a specific bug when certain conversion functions are called in a program compiled as mips16 with hard float and
the program is linked as c++. There are two libraries that are reversed in the link order with gcc/g++ and clang/clang++ for
mips16 in this case and the proper stubs will then not be called. These stubs are normally handled in the Mips16HardFloat pass
but in this case we don't know at that time that we need to generate the stubs. This must all be handled later in code generation
and we have moved this functionality to MipsAsmPrinter. When linked as C (gcc or clang) the proper stubs are linked in from libc.

2) Set up the infrastructure to handle 90% of what is in the Mips16HardFloat pass in this new area of MipsAsmPrinter. This is a more
logical place to handle this and we have known for some time that we needed to move the code later and not implement it using
inline asm as we do now but it was not clear exactly where to do this and what mechanism should be used. Now it's clear to us
how to do this and this patch contains the infrastructure to move most of this to MipsAsmPrinter but the actual moving will be done
in a follow on patch. The same infrastructure is used to fix this current bug as described in #1. This change was requested by the list
during the original putback of the Mips16HardFloat pass but was not practical for us do at that time.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201426 91177308-0d34-0410-b5e6-96231b3b80d8
Support DWARF discriminators in object streamer.

Summary:
This adds support for emitting DWARF path discriminator values in
the object streamer. It also changes the DWARF dumper to show
discriminator values in the line table output.

Reviewers: echristo

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2794

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201427 91177308-0d34-0410-b5e6-96231b3b80d8
DebugInfo: Don't include the name of the CU file in the line table file list when it's unneeded

Recommitting r201380 (reverted in r201389)
Recommitting r201351 and r201355 (reverted in r201351 and r201355)

We weren't emitting the an empty (header only) line table when the line
table was empty - this made the DWARF invalid (the compile unit would
point to the zero-size debug_lines section where there should've been an
empty line table but there was nothing at all). Fix that, and as a
consequence this works around/addresses PR18809.

Also, we emit a non-empty line table to workaround a darwin linker bug,
so XFAILing on darwin too.

Also, mark the test as 'REQUIRES: object-emission' because it does.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@201429 91177308-0d34-0410-b5e6-96231b3b80d8