Fix clash of gcc toolchains in hexagon driver regression tests.

If clang was configured with a custom gcc toolchain (either by using GCC_INSTALL_PREFIX in cmake or the equivalent configure command), the path to the custom gcc toolchain path takes precedence to the one specified by -ccc-install-dir. This causes several regression tests to fail as they will be using an unexpected path. Adding the switch --gcc-toolchain="" in each test command is not enough as the hexagon toolchain implementation in the driver is not evaluating this argument. This commit modifies the hexagon toolchain to take the --gcc-toolchain="" argument into account when deciding the toolchain path, similarly to what is already done for other targets toolchains. Additionally, the faulty regression tests are modified in order to --gcc-toolchain="" be passed to the commands.
Use StringRefMemoryObject in llvm-mc. NFC.
Don't redeclare a pure virtual method.

I.E., there is no value is having

void foo() override = 0;

If it is override it is already present in a base class. Since it is pure,
some other class will have to implement it.
[Mips] Do not hard-code the paired relocation type

Request `getPairRelocation()` function to get paired relocation type.
That allows us to look up another pairs like R_MICROMIPS_HI16/LO16
in the future.
SBValue::Cast is deprecated. This does not work as reliably as free-form casting via the expression evaluator. Some of our clients depend on it, so we can't remove it. But any new adopters should favor the expression parser as the way forward
This was meant to be count, not m_count
[ASan] Fix zero_page_pc test for PowerPC

Summary:
In the Power architecture, all branch instructions ignore the 2 least
significant bits of the target address. Consequently if you branch to an
invalid address, the address reported along with the SIGSEGV will have
been rounded down to a multiple of 4. Tweak this test accordingly.

This may fix the test for ARM too, in which case we could remove
the XFAIL, but I have no way of testing that.

Reviewers: kcc, willschm, glider, samsonov

Reviewed By: samsonov

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6167
R600: Remove unused define
Fix FileArchive member MemoryBuffer early destruction

When FileArchive loads a member, it instantiates a temporary MemoryBuffer
which points to the member range of the archive file.  The problem is that the
object file parsers call getBufferIndentifer() on that temporary MemoryBuffer
and store that StringRef as the _path data member for that lld::File.  When
FileArchive::instantiateMember() goes out of scope the MemoryBuffer is deleted
and the File::._path becomes a dangling reference.

The fix adds a vector<> to FileArchive to own the instantiated MemoryBuffers.
In addition it fixes member's path to be the standard format
(e.g. "/path/libfoo.a(foo.o)") instead of just the leaf name.
[mach-o] Add support for -order_file option

The darwin linker lets you rearrange functions and data for better locality
(less paging).  You do this with the -order_file option which supplies a text
file containing one symbol per line.

Implementing this required a small change to LayoutPass to add a custom sorter
hook.
Fix style.
Fix style.
Transform: add SymbolRewriter pass

This introduces the symbol rewriter. This is an IR->IR transformation that is
implemented as a CodeGenPrepare pass. This allows for the transparent
adjustment of the symbols during compilation.

It provides a clean, simple, elegant solution for symbol inter-positioning. This
technique is often used, such as in the various sanitizers and performance
analysis.

The control of this is via a custom YAML syntax map file that indicates source
to destination mapping, so as to avoid having the compiler to know the exact
details of the source to destination transformations.
Remove unused variable.
Safely generate new loop metadata node

Polly was accidently modifying a debug info metadata node when
attempting to generate a new unique metadata node for the loop id.
The problem was that we had dwarf metadata that referred to a
metadata node with a null value, like this:

  !6 = ... some dwarf metadata referring to !7 ...
  !7 = {null}

When we attempt to generate a new metadata node, we reserve the
first space for self-referential node by setting the first argument
to null and then mutating the node later to refer to itself.
However, because the nodes are uniqued based on pointer values, when
we get the new metadata node it actually referred to an existing
node (!7 in the example).  When we went to modify the metadata to
point to itself, we were accidently mutating the dwarf metatdata. We
ended up in this situation:

  !6 = ... some dwarf metadata referring to !7 ...
  !7 = {!7}

and this causes an assert when generating the debug info. The fix is
simple, we just need to use a unique value when getting a new
metadata node. The MDNode::getTemporary() provides exactly the API
we need (and it is used in clang to generate the unique nodes).

Differential Revision: http://reviews.llvm.org/D6174
PPC fix works for ARM, too
[mach-o] Fix MachOFileNode to own archives same as ELFFileNode

My previous fix to have FileArchive own the member MemoryBuffers was not a
complete solution for darwin because nothing owned the FileArchive object.
Fixed MachOFileNode to be like ELFFileNode and have the graph node own the
archive object.
[mach-o] remove stray debug output
Transforms: use typedef rather than using aliases

Visual Studio 2012 apparently does not support using alias declarations.  Use
the more traditional typedef approach.  This should let the Windows buildbots
pass.  NFC.
[Reassociate] Better preserve NSW/NUW flags.
Part of PR12985.

Phabricator Revision: http://reviews.llvm.org/D6172