[LLVMdev] seeking a mailing list for llvm ports

[Jim Grosbach]

Hi Peter,

While I’m not familiar with the OR1K port specifics, since it’s an out of tree port, you’re in the general right place for LLVM related questions, including about the assembler infrastructure.

You are correct that the .td files contain most of the information for instructions. All of it for simple instructions, really. Those files are used to create .inc files for asm matchers (it’s a bunch of data tables, and a few helper functions) via the tblgen utility.

The main assembler functionality is in the lib/MC library of llvm, with target specific bits in lib/Target/<targetname>/AsmParser. You can start by perusing that code a bit and stepping through the instruction matching. The llvm-mc utility is handy for this, as it’s a developer tool that provides a no-frills front end to the assembler and disassembler engines.

-Jim

> On Apr 27, 2015, at 1:49 PM, Peter T. Breuer <ptb at inv.it.uc3m.es> wrote:
> 
> Hi - sorry to intrude, but can somebody point me to a suitable mailing
> list where a tyro can get some advice on modifying an existing llvm
> llvm assembler ...  rather lightly?
> 
> I want to add an extra instruction to the assembler/machine code
> supported by the OR1K llvm port. 
> 
> Well, there are a few more things I need to do, but that will be
> good enough to start with!
> 
> I was able to what I wanted easily enough for gas, but I don't really
> see where to start with llvm.  The files that do the business seem to be
> those with ".td" suffixes (which look like they're written in a kind of
> ML, which is OK with me!).  Is that right?  I've tried making my
> additions in
> 
>  lib/Target/OR1K/OR1KInstrFormats.td
>  lib/Target/OR1K/OR1KInstrInfo.td
> 
> in the llvm (port) source. Surely there must be somewhere where my 
> attempts at additions should be referenced, from, however!  Where is
> that?
> 
> Regards, and hoping to get a pointer to where I should be posting!
> 
> PTB
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