After #139914, `DIBilder::finalize()` finalizes both declaration and
definition DISubprograms.
Therefore, there is no need to call `DIBuilder::finalizeSubprogram()`
right before `DIBilder::finalize()`.

Forward-fixes a compile error in bc216b057d (#150212) in specific build
configurations, due to a missing const_cast.

In current DebugLoc coverage builds, the output for any reasonably large
build can become very large if any missing DebugLocs are present; this
happens because single errors in LLVM may result in many errors being
reported in the output report. The main cause of this is that the empty
locations attached to instructions may be propagated to other
instructions in later passes, which will each be reported as new errors.
This patch prevents this by adding an "unknown" annotation to
instructions after reporting them once, ensuring that any other
DebugLocs copied or derived from the original empty location will not be
marked as new errors.

As a separate but related change, this patch updates the report
generation script to deduplicate results using the recorded stacktrace
if they are available, instead of the pass+instruction combination. This
reduces the size of the reduction, but makes the reduction highly
reliable, as the stacktrace allows us to very precisely identify when
two bugs have originated from the same place.

These are identified by misc-include-cleaner.  I've filtered out those
that break builds.  Also, I'm staying away from llvm-config.h,
config.h, and Compiler.h, which likely cause platform- or
compiler-specific build failures.

This is another prune of dead code -- we never generate debug intrinsics
nowadays, therefore there's no need for these codepaths to run.

---------

Co-authored-by: Nikita Popov <github@npopov.com>

This patch is part of a series that adds origin-tracking to the debugify
source location coverage checks, allowing us to report symbolized stack
traces of the point where missing source locations appear.

This patch completes the feature, having debugify handle origin stack
traces by symbolizing them when an associated bug is found and printing
them into the JSON report file as part of the bug entry. This patch also
updates the script that parses the JSON report and creates a
human-readable HTML report, adding an "Origin" entry to the table that
contains an expandable textbox containing the symbolized stack trace.

Patch 1/4 adding bitcode support.

Store whether or not a function is using Key Instructions in its DISubprogram so
that we don't need to rely on the -mllvm flag -dwarf-use-key-instructions to
determine whether or not to interpret Key Instructions metadata to decide
is_stmt placement at DWARF emission time. This makes bitcode support simple and
enables well defined mixing of non-key-instructions and key-instructions
functions in an LTO context.

This patch adds the bit (using DISubprogram::SubclassData1).

PR 144104 and 144103 use it during DWARF emission.
PR 44102 adds bitcode
support.

See pull request for overview of alternative attempts.

Seeing how we can't generate any debug intrinsics any more: delete a
variety of codepaths where they're handled. For the most part these are
plain deletions, in others I've tweaked comments to remain coherent, or
added a type to (what was) type-generic-lambdas.

This isn't all the DbgInfoIntrinsic call sites but it's most of the
simple scenarios.

Co-authored-by: Nikita Popov <github@npopov.com>

Change in #107278 modified the CMake CACHE variable with values
that are not supported for it as documented. This patch renames the
derived vars so that they do not conflict with the CACHE variable.

This patch transforms:

  X && *X == Y

to:

  X == Y

where X is of std::optional<T>, and Y is of T or similar.