Changes

[lld] Silence compiler warnings by removing always true/false comparisons

type is an uint8_t so
 type >= 0
is always true and
 type < 0
is always false.

[SCEV] Use ListSeparator (NFC)

[llvm] Fix header guards (NFC)

Identified with llvm-header-guard.

[CodeGen] Use range-based for loops (NFC)

[SampleFDO] Fix MSVC "namespace uses itself" warning (NFC)

MSVC warning:
```
SampleProfileLoaderBaseImpl.h(41): warning C4515: 'llvm': namespace uses itself
```

tsan: don't leave unmapped hole in non-app memory

If an app mmaps lots of memory, a user mmap may end up
in the tsan region for traces. Shadow for this range
overlaps with shadow for other user regions.
This causes havok: from false positives to crashes.
Don't leave unmapped holes in the traces region.

Reviewed-in: https://reviews.llvm.org/D96697

[vim] Add initial syntax definition for .mir files

This initial definition handles the yaml container and the embedding of
the inner IRs. As a stopgap, this reuses the LLVM IR syntax highlighting
for the MIR function bodies--even though it's not technically correct,
it produces decent highlighting for a first pass.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D95552

[vim] Highlight most common MIR syntax not in LLVM IR

This adds highlighting for MIR instruction opcodes, physical registers,
and MIR types.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D95553

[OpenMP] Fix a warning on an unused variable

[clang][Frontend] Fix a crash in DiagnosticRenderer.

Displaying the problem range could crash if the begin and end of a
range is in different files or macros. After the change such range
is displayed only as the beginning location.

There is a bug for this problem:
https://bugs.llvm.org/show_bug.cgi?id=46540

Reviewed By: steakhal

Differential Revision: https://reviews.llvm.org/D95860

[sanitizers] Pass CMAKE_C_FLAGS into TSan buildgo script

When compiling with ccache, compiler commands get split into smaller steps
and clang's default -Wunused-command-line-argument complains about unused
include directory arguments. In combination -Werror, compilation aborts.

This patch passes the CMAKE_C_FLAGS into the build script. Configuring with
-DCMAKE_C_FLAGS=-Wno-unused-command-line-argument allows successful testing.

Differential Revision: https://reviews.llvm.org/D96762

[MachineSink] Add a loop sink limit

To make sure compile-times don't regress, add an option to restrict the number
of instructions considered for sinking as alias analysis can be expensive and
for the same reason also skip large blocks.

Differential Revision: https://reviews.llvm.org/D96485