Changes

[LegalizeDAG] Convert strict fp nodes to libcalls without losing the
chain.
Previously we mutated the node and then converted it to a libcall. But
this loses the chain information.
This patch keeps the chain, but unfortunately breaks tail call
optimization as the functions involved in deciding if a node is in tail
call position can't handle the chain. But correct ordering seems more
important to be right.
Somehow the SystemZ tests improved. I looked at one of them and it
seemed that we're handling the split vector elements in a different
order and that made the copies work better.
Differential Revision: https://reviews.llvm.org/D70334

Implement __attribute__((objc_direct)),
__attribute__((objc_direct_members))
__attribute__((objc_direct)) is an attribute on methods declaration, and
__attribute__((objc_direct_members)) on implementation, categories or 
extensions.
A `direct` property specifier is added (@property(direct) type name)
These attributes / specifiers cause the method to have no associated 
Objective-C metadata (for the property or the method itself), and the 
calling convention to be a direct C function call.
The symbol for the method has enforced hidden visibility and such direct 
calls are hence unreachable cross image. An explicit C function must be 
made if so desired to wrap them.
The implicit `self` and `_cmd` arguments are preserved, however to 
maintain compatibility with the usual `objc_msgSend` semantics, 3
fundamental precautions are taken:
1) for instance methods, `self` is nil-checked. On arm64 backends this
  typically adds a single instruction (cbz x0, <closest-ret>) to the
  codegen, for the vast majority of the cases when the return type is a
  scalar.
2) for class methods, because the class may not be realized/initialized
  yet, a call to `[self self]` is emitted. When the proper deployment
  target is used, this is optimized to `objc_opt_self(self)`.
   However, long term we might want to emit something better that the
  optimizer can reason about. When inlining kicks in, these calls
  aren't optimized away as the optimizer has no idea that a single call
  is really necessary.
3) the calling convention for the `_cmd` argument is changed: the caller
  leaves the second argument to the call undefined, and the selector is
  loaded inside the body when it's referenced only.
As far as error reporting goes, the compiler refuses:
- making any overloads direct,
- making an overload of a direct method,
- implementations marked as direct when the declaration in the
 interface isn't (the other way around is allowed, as the direct
 attribute is inherited from the declaration),
- marking methods required for protocol conformance as direct,
- messaging an unqualified `id` with a direct method,
- forming any @selector() expression with only direct selectors.
As warnings:
- any inconsistency of direct-related calling convention when
 @selector() or messaging is used,
- forming any @selector() expression with a possibly direct selector.
Lastly an `objc_direct_members` attribute is added that can decorate
`@implementation` blocks and causes methods only declared there (and in 
no `@interface`) to be automatically direct. When decorating an
`@interface` then all methods and properties declared in this block are 
marked direct.
Radar-ID: rdar://problem/2684889 Differential Revision:
https://reviews.llvm.org/D69991 Reviewed-By: John McCall

[X86] Add AMD Matisse (znver2) model number to getHostCPUName and
compiler-rt's getAMDProcessorTypeAndSubtype.
This is the CPUID model used on Ryzen 3000 series (Zen 2/Matisse) CPUs.
Patch by Alex James
Differential Revision: https://reviews.llvm.org/D70279

[ThinLTO] Promotion handling cleanup (NFC)
Summary: Clean up the code that does GV promotion in the ThinLTO
backends.
Specifically, we don't need to check whether we are importing since that 
is already checked and handled correctly in shouldPromoteLocalToGlobal. 
Simply call shouldPromoteLocalToGlobal, and if it returns true we are 
guaranteed that we are promoting, whether or not we are importing (or in 
the exporting module). This also makes the handling in getName() 
consistent with that in getLinkage(), which checks the DoPromote
parameter regardless of whether we are importing or exporting.
Reviewers: steven_wu, pcc, evgeny777
Subscribers: mehdi_amini, inglorion, hiraditya, dexonsmith, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70327

Update the docs for building libc++.
Summary: Rewrite the in-tree build to be a clearer tl;dr like we have
for the out-of-tree build.
Reviewers: EricWF, mclow.lists, ldionne
Reviewed By: ldionne
Subscribers: dexonsmith, christof, ldionne, enh, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D69917

[Sema] Fix a -Wobjc-signed-char-bool false-positive
Unsigned bit-field flags can only have boolean values, so handle that
case in Expr::isKnownToHaveBooleanValue.
rdar://56256999

[X86] Add a 'break;' to the end of the last case in a switch to avoid
surprising the next person to add a case after this one. NFC

Fix _LIBCPP_HAS_ definitions for Android.
Summary: Android added quick_exit()/at_quick_exit() in API level 21, 
aligned_alloc() in API level 28, and timespec_get() in API level 29, but
has the other C11 features at all API levels (since they're basically 
just coming from clang directly).
_LIBCPP_HAS_QUICK_EXIT and _LIBCPP_HAS_TIMESPEC_GET already existed, so
we can reuse them. (And use _LIBCPP_HAS_TIMESPEC_GET in a few more 
places where _LIBCPP_HAS_C11_FEATURES has been used as a proxy. This 
isn't correct for Android.)
_LIBCPP_HAS_ALIGNED_ALLOC is added, to cover aligned_alloc()
(obviously).
Add a missing std:: before aligned_alloc in a cstdlib test, and remove a 
couple of !defined(_WIN32)s now that we're explicitly testing 
TEST_HAS_ALIGNED_ALLOC rather than TEST_HAS_C11_FEATURES.
Reviewers: danalbert, EricWF, mclow.lists
Reviewed By: danalbert
Subscribers: srhines, christof, libcxx-commits
Tags: #libc
Differential Revision: https://reviews.llvm.org/D69929

implement printing out raw section data of xcoff objectfile for
llvm-objdump
SUMMARY: implement printing out raw section data of xcoff objectfile for
llvm-objdump and option -D --disassemble-all option for llvm-objdump
Reviewers: Sean Fertile Subscribers: rupprecht, seiyai,hiraditya
Differential Revision: https://reviews.llvm.org/D70255