[PATCH] D88603: [WebAssembly] Add support for DWARF type units

David Blaikie via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Wed Oct 28 19:42:11 PDT 2020


dblaikie added a comment.

In D88603#2360845 <https://reviews.llvm.org/D88603#2360845>, @dschuff wrote:

> @sbc100 I found that the cause of the assertion is that 
> in dwarf 5, the type units apparently go in the .debug_info section (instead of the .debug_type section), and this section already exists (but it was created as a non-comdat).
> So when `getWasmSection` tries to look up an existing section it fails because the group is part of the key. Then it tries to create a new section but that fails because the name is duplicate.
>
> For some reason this doesn't happen or is not a problem with ELF but I haven't looked up why yet.
> For now I just disabled the dwarf5+TU tests since we don't really use dwarf5 yet anyway.

for ELF, each {section name, hash} pair denotes a distinct section (when using SHF_GROUP). Linker's deduplicate the group based on the hash, then squish all the distinct sections with the same name together. (same system that powers -ffunction-sections -fno-unique-section-names - even though each function section is called ".text", because they have different hashes and use SHF_GROUP, they are distinct sections in the object file)


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