This patch introduces a new virtual method
`TargetInstrInfo::isSafeToMove()` to allow backends to control whether a
machine instruction can be safely moved by optimization passes.

The `BranchFolder` pass now respects this hook when hoisting common
code. By default, all instructions are considered safe to to move.

For LoongArch, `isSafeToMove()` is overridden to prevent
relocation-related instruction sequences (e.g. PC-relative addressing
and calls) from being broken by instruction motion. Correspondingly,
`isSchedulingBoundary()` is updated to reuse this logic for consistency.

Relands #163725

(cherry picked from commit ea10026b64f66b3b69c0545db20f9daa8579f5cb)

This was causing a build failure on Darwin and a test failure on Linux.
This config is not widely used or well tested, so I don't think the
potential and likely small performance gains and the portability from
this are worth the maintenance costs.

(cherry picked from commit 1906c3e1e30759d2eb85b2833e8c5ff64128bfba)

As reported in <https://github.com/llvm/llvm-project/issues/166870>,
some copies with src==reg are not no-ops, e.g. when self-assigning a
w-reg on AArch64 which will zero-extend the corresponding x register.

Revert in order to fix the issue. We may revisit whether the
optimisation can be made safe at a later point.

Reverts dffbc030e75b758e7512518abd499a0f680addbf.
Fixes #166870.

(cherry picked from commit a314b3b401b5f9e6218d863bfcc29393e1b6f447)

We need to take into account that we may have already done a FirstSPAdjust.

Fixes #164805.

(cherry picked from commit ff11b93bb8f5578c9eb7296160570ea001a1155f)

Fixes #165445.

Fixes a crash when `ASTWriter::GenerateNameLookupTable` processes enum
constants from C++20 header units.

The special handling for enum constants, introduced in fccc6ee, doesn't
account for declarations whose owning module is a C++20 header unit. It
calls `isNamedModule()` on the result of
`getTopLevelOwningNamedModule()`, which returns null for header units,
causing a null pointer dereference.

(cherry picked from commit bc08e69959ecefecc7ea41b648a659aa19c458c8)

This patch just copies the definitions from main, which should be working.
There are a lot of changes that were not explicitly backported.

The VM_MEMORY_SANITIZER constant was added in macOs 10.15 and friends.
Support using the constant on older OSes.

Fixes #156144

(cherry picked from commit bc55f4f4f2b4ef196cf3ec25f69dfbd9cd032237)

Fix https://github.com/llvm/llvm-project/issues/156679

There is a mismatch between the preprocessor guards around the include
of `hwloc.h` and those protecting its usages, leading to build failures
on Darwin: https://github.com/spack/spack-packages/pull/1212

This change introduces `KMP_HWLOC_ENABLED` that reflects
whether hwloc is actually used.

(cherry picked from commit cd24d108a2c19c23c4ac80b501fa7361963cca3d)

Haiku requires linking in libnetwork.

Co-authored-by: Jérôme Duval <jerome.duval@gmail.com>
(cherry picked from commit 21bcd00e54416b0950da19fe8adb0628a19bf66f)