This to protect against non-sensical instruction sequences being assembled,
which would either cause asserts/crashes further down, or a Wasm module being output that doesn't validate.
Unlike a validator, this type checker is able to give type-errors as part of the parsing process, which makes the assembler much friendlier to be used by humans writing manual input.
Because the MC system is single pass (instructions aren't even stored in MC format, they are directly output) the type checker has to be single pass as well, which means that from now on .globaltype and .functype decls must come before their use. An extra pass is added to Codegen to collect information for this purpose, since AsmPrinter is normally single pass / streaming as well, and would otherwise generate this information on the fly.
A `-no-type-check` flag was added to llvm-mc (and any other tools that take asm input) that surpresses type errors, as a quick escape hatch for tests that were not intended to be type correct.
This is a first version of the type checker that ignores control flow, i.e. it checks that types are correct along the linear path, but not the branch path. This will still catch most errors. Branch checking could be added in the future.
Differential Revision: https://reviews.llvm.org/D104945
When running in relocatable mode any input data segments that are part
of a comdat group should not be merged with other segments of the same
name. This is because the final linker needs to keep the separate so
they can be included/excluded individually.
Often this is not a problem since normally only one section with a given
name `foo` ends up in the output object file. However, the problem
occurs when one input contains `foo` which part of a comdat and another
object contains a local symbol `foo` we were attempting to merge them.
This behaviour matches (I believe) that of the ELF linker. See
`LinkerScript.cpp:addInputSec`.
Fixes: https://github.com/emscripten-core/emscripten/issues/9726
Differential Revision: https://reviews.llvm.org/D101703
Wouter van Oortmerssen