Changes

[mlir] Canonicalize AllocOp's with only store and dealloc uses

Differential Revision: https://reviews.llvm.org/D100268

[Polly] Fix stage 2 clang -Wdeprecated-copy after D79714

[lldb] [Process] Introduce protocol extension support API

Introduce a NativeProcessProtocol API for indicating support for
protocol extensions and enabling them.  LLGS calls
GetSupportedExtensions() method on the process factory to determine
which extensions are supported by the plugin.  If the future is both
supported by the plugin and reported as supported by the client, LLGS
enables it and reports to the client as supported by the server.

The extension is enabled on the process instance by calling
SetEnabledExtensions() method.  This is done after qSupported exchange
(if the debugger is attached to any process), as well as after launching
or attaching to a new inferior.

The patch adds 'fork' extension corresponding to 'fork-events+'
qSupported feature and 'vfork' extension for 'vfork-events+'.  Both
features rely on 'multiprocess+' being supported as well.

Differential Revision: https://reviews.llvm.org/D100153

[lldb] [gdb-remote server] Introduce new stop reasons for fork and vfork

Introduce three new stop reasons for fork, vfork and vforkdone events.
This includes server support for serializing fork/vfork events into
gdb-remote protocol.  The stop infos for the two base events take a pair
of PID and TID for the newly forked process.

Differential Revision: https://reviews.llvm.org/D100196

[lldb] [llgs] Support owning and detaching extra processes

Add a NativeDelegate API to pass new processes (forks) to LLGS,
and support detaching them via the 'D' packet.  A 'D' packet without
a specific PID detaches all processes, otherwise it detaches either
the specified subprocess or the main process, depending on the passed
PID.

Differential Revision: https://reviews.llvm.org/D100191

[lldb] [Process/Linux] Report fork/vfork stop reason

Enable reporting fork/vfork events to the server when supported.
At this moment, this is used only to test the server code, as real
client does not report fork-events and vfork-events as supported.

Differential Revision: https://reviews.llvm.org/D100208

[Polly][ManualOpt] Match interpretation of unroll metadata to LoopUnrolls's.

We previously had a different interpretation of unroll transformation
attributes than how LoopUnroll interpreted it. In particular,
llvm.loop.unroll.enable was needed explicitly to enable it and disabling
metadata was ignored.
Additionally, it required that either full unrolling or an unroll factor
to be specified or fail otherwise. An unroll factor is still required,
but the transformation is ignored with the hope that LoopUnroll is going
to apply the unrolling, since Polly currently does not implement an
heuristic.

Fixes llvm.org/PR50109

[InstCombine] Added testcases from PR48999, NFC

[GVN] Clobber partially aliased loads.

Use offsets stored in `AliasResult` implemented in D98718.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D95543

[lld/mac] add test coverage for -sectcreate and -order_file with --reproduce

Would've caught the (since fixed) regression in D97610.

No behavior change.

Differential Revision: https://reviews.llvm.org/D101218

[lld/mac] simplify export-options.s test a bit

- the macro seems needlessly clever -- shorter and imho clearer without it
- give all filenames an extension so they look like filenames
- rename .private_extern symbol from _private to _private_extern
  to prepare for follow-up that adds a truly private symbol

No behavior change.

Differential Revision: https://reviews.llvm.org/D101222