[llvm-dev] Mapping from IR instructions to MIR?

Jeremy Morse via llvm-dev llvm-dev at lists.llvm.org
Thu Jan 30 05:53:32 PST 2020

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.


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