[llvm-dev] Assembly file compilation flow

[David Chisnall via llvm-dev]

On 10 May 2018, at 21:55, via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> I think a key point to understand is the MCStreamer interface, which has two implementations: one for object-file generation, and one for .s file generation.  CodeGen/AsmPrinter can attach to either of these implementations.  MCAsmParser will generally attach to the object-file version of MCStreamer.

Note that it is possible (even via the llvm-mc command-line interface) to attach it to the assembly back end, so you can parse assembly and generate assembly.  This can be interesting on architectures such as MIPS that include a lot of pseudos, because it will expand them to individual instructions (MIPS dla, for example, expands to one of 4 different things depending on assembler state and target).

This path is also used in testing, to ensure that assembly instructions are parsed to their canonical representation.

David