The result of the function cannot be correctly interpreted without
knowing the precise form type (a type signature needs to be looked up
very differently from a supplementary debug info reference). The
function sort of worked because the two reference types (unit-relative
and section-relative) that can be handled uniformly are also the most
common types of references, but this setup made it easy to write code
which does not support other kinds of reference (and if one tried to
support them, the result didn't look pretty --
https://github.com/llvm/llvm-project/pull/97423/files#r1676217081).

The split is based on the reference type classification from DWARFv5
(Section 7.5.5 Classes and Forms), and it should enable uniform (if
slightly more verbose) hadling. Note that this only affects users which
want more control of how (or if) the references are resolved. Users
which just want to access the referenced DIE can use the higher level
API (DWARFDie::GetAttributeValueAsReferencedDie) which returns (or will
return after #97423 is merged) the correct die for all reference types
(except for supplementary references, which we don't support right now).

This revision implement new mechanism for DWARFRewriter.
In the new mechanism, we adopt the same way with DWARFLinker did.
By parsing Debug information into IR, we are allowed to handle debug information more flexible.
Now the debug information updating process relies on IR and IR will be written out to binary once the updating finished.

A new class was added: DIEBuilder. This class is responsible for parsing debug information and raising it to the IR level.
This class is also used to write out the .debug_info and .debug_abbrev sections.
Since we output brand new Abbrev section we won't need to always convert low_pc/high_pc into ranges.
When conversion does happen we can also remove low_pc entry.

Reviewed By: maksfb, ayermolo

Differential Revision: https://reviews.llvm.org/D130315

This reverts commit 460a2244430fae192298a5fd9fa2a269e540e8c1.
It breaks building on macOS, and it was landed with a review URL
pointing to some Facebook-internal service.

Also reverts a bunch of follow-ups:

Revert "[BOLT][DWARF] Don't check string offsets"
This reverts commit f9d6f48c8bf5acaac07502403c41cf0b0d89c8d2.

Revert "[BOLT][DWARF] Change to process and write out TUs first then CUs in batches"
This reverts commit 88e95c1e4bb6e2ad3bfd185b96341ad5c09eff6b.

Revert "[BOLT][DWARF] Output DWO files as they are being processed"
This reverts commit 46ca2e3fcd419b1246357ed3b9cd36630f16e64d.

Revert "[BOLT][DWARF] Don't check string offsets"
This reverts commit cfe4a4b04f219a9dbb4e3fc01883437b6ff0e702.

Revert "[BOLT][DWARF] Numerous fixes for a new DWARFRewriter"
This reverts commit 2701a661daa393ad5901ac88d420d7aa931eda0d.

Summary:
This revision implement new mechanism for DWARFRewriter.
In the new mechanism, we adopt the same way with DWARFLinker did.
By parsing Debug information into IR, we are allowed to handle debug information more flexible.
Now the debug information updating process relies on IR and IR will be written out to binary once the updating finished.

A new class was added: DIEBuilder. This class is responsible for parsing debug information and raising it to the IR level.
This class is also used to write out the .debug_info and .debug_abbrev sections.
Since we output brand new Abbrev section we won't need to always convert low_pc/high_pc into ranges.
When conversion does happen we can also remove low_pc entry.

Differential Revision: https://phabricator.intern.facebook.com/D39484421

Tasks: T117448832

DW_FORM_line_strp reads from the .debug_line_str section, but
previously the out-of-bounds error reported the .debug_line section.

This incorrect error message showed up when debugging an issue with
some invalid DWARF5 data.

The verify_string.s test has now been extended to check this (which
required a small change to the DWARF verifier to also look at
DW_FORM_line_strp).

Differential Revision: https://reviews.llvm.org/D146539

The result of DWARFFormValue::isFormClass depends on DWARF version in some cases.
The current implementation takes DWARF version from the stored DWARFUnit.
If there is no stored DWARFUnit then the current behavior is to assume
DwarfVersion <= 3. This patch adds new function which has a DWARF version as a
parameter so it is possible to check form class for various DWARF versions.

Differential Revision: https://reviews.llvm.org/D145499

This fixes a few places where the addrx3 and strx3 forms were missed.
Previously this meant if one of these forms appeared somewhere various
errors could occur. This now also adds an extra test case for the addrx3
form (which previously failed).

Differential Revision: https://reviews.llvm.org/D143488

Previously this would incorrectly return the raw offset into the .debug_addr section for the
DW_FORM_addrx1/2/3/4 forms rather than the actual address.

Note that this was handled correctly in the dump() function so this issue only occurs for users
of this API and not in tools such as llvm-dwarfdump. The dump() method has now been updated
to use this method to increase coverage.

This also now adds a few unit tests for indexed addresses to DWARFDebugInfoTest.

Differential Revision: https://reviews.llvm.org/D143073