llvm dev - Jan 2020 - Mapping from IR instructions to MIR?

Hi all,

I'd like to use LLVM to generate a total mapping from IR instructions to
their lowered MIR counterpart(s), post all gMIR/legalization/ISel passes.
However, I'm having trouble figuring out whether this is currently
supported somewhere in the backend/has a known correct approach.

Does anybody know if this is something currently do-able within the
backend? I've run into a bit of a dead end with IRTranslator. There's
also
a comment in LegalizerHelper.h that suggests the presence of configurable
"RecordInsertInstruction" functions[1], but I can't find any other
references to it.

Thanks!
William Woodruff

[1]:
https://github.com/llvm/llvm-project/blob/a9af1dc34d33762751958a91aa8b82b856c2077a/llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h#L91
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Hi William,

On Wed, Jan 29, 2020 at 4:21 PM William Woodruff via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> I'd like to use LLVM to generate a total mapping from IR instructions
to their lowered MIR counterpart(s), post all gMIR/legalization/ISel passes.
However, I'm having trouble figuring out whether this is currently supported
somewhere in the backend/has a known correct approach.
Does debugging information fit your use case? An IR instruction's
DebugLoc tracks its line number (and more), which is preserved through
to the corresponding MIR instructions.

Due to the optimisations involved in isel, I don't think it's
guaranteed that an IR instruction has to have one corresponding MIR
instruction, there can be several, or none.

--
Thanks,
Jeremy