Credits for this description go to @ftynse in
<https://discourse.llvm.org/t/scf-dialect-vs-cfg/3524/2> and
@antiagainst in
<https://www.lei.chat/posts/mlir-codegen-dialects-for-machine-learning-compilers/>!
(Unless it's wrong of course, then it's my bad.)

EDIT: Also related:
<https://discourse.llvm.org/t/codegen-dialect-overview/2723

>.

---------

Co-authored-by: Mehdi Amini <joker.eph@gmail.com>

Factor out some stack allocation in a separate function. This patch
splits out the generic portion of a larger refactoring done as a part of
stack clash protection support.

The patch is almost, but not quite NFC. The only difference should
be that where we have adjacent allocation of stack space
for local SVE objects and non-local SVE objects the order
of `sub sp, ...` and `addvl sp, ...` instructions is reversed, because now
it's done with a single call to `emitFrameOffset` and it happens
add/subtract the fixed part before the scalable part, e.g.

    addvl sp, sp, #-2
    sub sp, sp, #16, lsl #12
    sub sp, sp, #16

becomes

    sub sp, sp, #16, lsl #12
    sub sp, sp, #16
    addvl sp, sp, #-2

Patch 3/3 of the transition step 1 described in

https://discourse.llvm.org/t/rfc-enabling-the-hlfir-lowering-by-default/72778/7

This patch changes bbc and flang-new driver to use HLFIR lowering by
default.

`-hlfir=false` can be used with bbc and `-flang-deprecated-no-hlfir`
with flang-new to get the previous default lowering behavior, but these
options will only be available for a limited period of time.

If any user needs these options to workaround bugs, they should open an
issue against flang in llvm github repo so that the regression can be
fixed in HLFIR.

This reverts commit 9a9933fa.

The OCaml bindings were using `LLVMDIBuilderCreateStaticMemberType`,
causing the API change in `9a9933fa`
to break buildbots that built the bindings. Revert until we figure out
whether to fixup the bindings or just not change the C-API

Due to a GCC bug (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25940),
GCC doesn't consider extern "C" functions with the same name but
different namespace to be the same. As such, the default visibility
attribute (on a declaration outside the namespace) doesn't get applied
to the definition in the namespace and the symbol is not exported.

This came up as an ABI diff when switching between gcc and clang for
compiling compiler-rt.

FileCheck currently compiles a regular expression of the form
`Prefix1|Prefix2|...` and uses it to find the next prefix in the input.

If we had a fast regex implementation, this would be a useful thing to
do, as the regex implementation would be able to match multiple prefixes
more efficiently than a naive approach. However, with our actual regex
implementation, finding the prefixes basically becomes O(InputLen *
RegexLen * LargeConstantFactor), which is a lot worse than a simple
string search.

Replace the regex with StringRef::find(), and keeping track of the next
position of each prefix. There are various ways this could be improved
on, but it's already significantly faster that the previous approach.

For me, this improves check-llvm time from 138.5s to 132.5s, so by
around 4-5%.

For vector-interleaved-load-i16-stride-7.ll in particular, test time
drops from 5s to 2.5s.

This patch adds the LLVM-side infrastructure to implement DWARFv5 issue
161118.1: "DW_TAG for C++ static data members".

The clang-side of this patch will simply construct the DIDerivedType
with a different DW_TAG.

Fix indentation, naming and capitalization to match current style
guides.

EvaluateAsConstantExpr() uses ::EvaluateInPlace() directly, which does
not use the new interpreter if requested. Do it here, which is the same
pattern we use in EvaluateAsInitializer.

This was a combination of issues:
  1) We can subtract pointers that don't point into arrays.
  2) In C, everything is possible.

https://github.com/llvm/llvm-project/pull/70958 adds registers R16-R31
(EGPR), this patch


1. Supports decoding of EGPR for instruction w/ REX2 prefix
2. Supports decoding of EGPR for instruction w/ EVEX prefix

For simplicity's sake,  we 
1.  Simulate the REX prefix w/ the 1st payload of REX2
2.  Simulate the REX2 prefix w/ the 2nd and 3rd payloads of EVEX

RFC:

https://discourse.llvm.org/t/rfc-design-for-apx-feature-egpr-and-ndd-support/73031/4

Explanations for some changes:
1. invalid-EVEX-R2.txt is deleted b/c `0x62 0xe1 0xff 0x08 0x79 0xc0` is
valid and decoded to `vcvtsd2usi %xmm0, %r16` now.
2. One line in x86-64-err.txt is removed b/c APX relaxes the limitation
of the 1st and 2nd payloads of EVEX prefix, so the error message changes

The first commit extends the capacity from the compiler infrastructure,
and the second commit continues the effort in #71140 to introduce tuple
types for bfloat16.

Allowed lexers are documented in https://pygments.org/docs/lexers/.

Just a minor fix for the section depth for the patch in
https://reviews.llvm.org/D155029.

[X86][MC] Remove duplicated code in X86DisassemblerDecoder.h by defining macro helpers (NFCI) (#72341)

memref.atomic_rmw will fail to convert for memref types that have an offset because they do not have identity maps. This restriction is overly conservative, so this changes the restriction to only strided memref types.

Very little of it needs to be public.

The tests for 'b' which commented with FIXME are incorrect, the
following patch will fix it.

This is partially based on AArch64, but reduced to handle just the case
we currently have a test for.

suggested in review of https://github.com/llvm/llvm-project/pull/69553

This is actually not an NFC as isFunction() does not return false for
some "invalid" object, instead it returns the errors to its caller. But
since there is no such invalid object in the LIT tests, so no case
changes.

The R_LARCH_{ADD,SUB}6 relocation type are usually used by DwarfCFA to
calculate a tiny offset. They appear after binutils 2.41, with GAS
enabling relaxation by default.

This patch adds support for saving minidumps with the arm64
architecture. It also will cause unsupported architectures to emit an
error where before this patch it would emit a minidump with partial
information. This new code is tested by the arm64 windows buildbot that
was failing:

https://lab.llvm.org/buildbot/#/builders/219/builds/6868

This is needed following this PR:
https://github.com/llvm/llvm-project/pull/71772

This PR separates parts of the symbolizer markup
implementation that are Fuchsia OS specific. This
is in preparation of enabling symbolizer markup
in other OSs.

SelectionDAG does the same thing in 74c83649

These variables are used by other platforms as well.

This was important when typed LLVM pointers wanted a struct definition
for every type, but that's no longer necessary with opaque pointers.
NFCI.

We don't allow SCUDO_OPTIONS to be preserved across SELinux transitions,
so introducing a more constrained one that we can preserve.

Prevent a null pointer exception for allocation_ring_buffer_size < 0.

Fixes https://github.com/llvm/llvm-project/issues/72194.

```
---------------------------------------------------
Benchmark                       old             new
---------------------------------------------------
bm_for_each/1               3.00 ns         2.98 ns
bm_for_each/2               4.53 ns         4.57 ns
bm_for_each/3               5.82 ns         5.82 ns
bm_for_each/4               6.94 ns         6.91 ns
bm_for_each/5               7.55 ns         7.75 ns
bm_for_each/6               7.06 ns         7.45 ns
bm_for_each/7               6.69 ns         7.14 ns
bm_for_each/8               6.86 ns         4.06 ns
bm_for_each/16              11.5 ns         5.73 ns
bm_for_each/64              43.7 ns         4.06 ns
bm_for_each/512              356 ns         7.98 ns
bm_for_each/4096            2787 ns         53.6 ns
bm_for_each/32768          20836 ns          438 ns
bm_for_each/262144        195362 ns         4945 ns
bm_for_each/1048576       685482 ns        19822 ns
```

Reviewed By: ldionne, Mordante, #libc

Spies: bgraur, sberg, arichardson, libcxx-commits

Differential Revision: https://reviews.llvm.org/D151274

The tryMergeAdjacentSTG function tries to merge multiple
stg/st2g/stg_loop instructions. It doesn't verify the liveness of NZCV
flag before moving around STGloop which also alters NZCV flags. This was
not issue before the patch 5e612bc2 as these stack tag stores does not
alter the NZCV flags. But after the change, this merge function leads to
miscompilation because of control flow change in instructions. Added the
check to to see if the first instruction after insert point reads or
writes to NZCV flag and it's liveout state. This check happens after the
filling of merge list just before merge and bails out if necessary.

This fixes all the warnings of the following type in the CI
(https://lab.llvm.org/buildbot/#/builders/89/builds/50248/steps/5/logs/stdio)
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