This reverts commit 11d61c079d4b4927efea42a38a27d4586887b764 to re-apply
6836a47b7e6b57927664ec6ec750ae37bb951129 with modifications.

Specifically, the errors in DWARFAbbreviationDeclaration::extract needed
to be moved as they are returned to ensure the right Error constructor
is selected.

This reverts commit 6836a47b7e6b57927664ec6ec750ae37bb951129.
This breaks some bots, need to investigate.

In trying to hoist errors further up this callstack, I discovered that
if the data in the debug_abbrev section is invalid entirely, the code
that parses the debug_abbrev section may do strange or unpredictable
things. The underlying issue is that DataExtractor will return a value
of 0 when it encounters an error in extracting a LEB128 value. It's thus
difficult to determine if there was an error just by looking at the
return value. This patch aims to bail at the first sight of an error in
the debug_abbrev parsing code.

Differential Revision: https://reviews.llvm.org/D151755

The motivation behind this refactor is to be able to use
DWARFAbbreviationDeclaration from LLDB. LLDB has its own implementation
of DWARFAbbreviationDeclaration that is very similar to LLVM's but it
has different semantics around error handling.

This patch modifies llvm::DWARFAbbreviationDeclaration::extract to
return an `llvm::Expected<ExtractState>` to differentiate between "I am
done extracting" and "An error has occured", something which the current
return type (bool) does not accurately capture.

Differential Revision: https://reviews.llvm.org/D150607

These source files no longer use Optional<T>, so they do not need to
include Optional.h.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

These source files no longer use None, so they do not need to include
None.h.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

This patch mechanically replaces None with std::nullopt where the
compiler would warn if None were deprecated.  The intent is to reduce
the amount of manual work required in migrating from Optional to
std::optional.

This is part of an effort to migrate from llvm::Optional to
std::optional:

https://discourse.llvm.org/t/deprecating-llvm-optional-x-hasvalue-getvalue-getvalueor/63716

As usual with that header cleanup series, some implicit dependencies now need to
be explicit:

llvm/DebugInfo/DWARF/DWARFContext.h no longer includes:
- "llvm/DebugInfo/DWARF/DWARFAcceleratorTable.h"
- "llvm/DebugInfo/DWARF/DWARFCompileUnit.h"
- "llvm/DebugInfo/DWARF/DWARFDebugAbbrev.h"
- "llvm/DebugInfo/DWARF/DWARFDebugAranges.h"
- "llvm/DebugInfo/DWARF/DWARFDebugFrame.h"
- "llvm/DebugInfo/DWARF/DWARFDebugLoc.h"
- "llvm/DebugInfo/DWARF/DWARFDebugMacro.h"
- "llvm/DebugInfo/DWARF/DWARFGdbIndex.h"
- "llvm/DebugInfo/DWARF/DWARFSection.h"
- "llvm/DebugInfo/DWARF/DWARFTypeUnit.h"
- "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"

Plus llvm/Support/Errc.h not included by a bunch of llvm/DebugInfo/DWARF/DWARF*.h files

Preprocessed lines to build llvm on my setup:
after: 1065629059
before: 1066621848

Which is a great diff!

Discourse thread: https://discourse.llvm.org/t/include-what-you-use-include-cleanup
Differential Revision: https://reviews.llvm.org/D119723

This is used by BOLT to do patching of DebugInfo section, and Line Table. Directly by using find, and through getAttrFieldOffsetForUnit.

Reviewed By: dblaikie

Differential Revision: https://reviews.llvm.org/D107874