[llvm-dev] Support for out-of-tree backend passes?

[William Woodruff via llvm-dev]

On Mon, Mar 04, 2019 at 05:26:16PM -0500, Nemanja Ivanovic wrote:
>    Don't forget that the back end lowers LLVM IR to
>    SDAG, then the SDAG is selected, converted into SSA MIR, then RA and
>    rewriting happens to take it out of SSA and finally it lowers to the MC
>    layer. It would be ambiguous to invoke  llc -my-pass unless we are
>    restricting the passes to IR->IR ones, restricting it to
>    pre-codegenprep and generally imposing the same requirements on the
>    passes as exist in the middle end.

Excellent points. My use case does indeed involve just IR->IR,
but there's not much point in exposing the back-end if more
diverse cases don't benefit from it.

In the mean time, I've been successfully implementing what I want
with a combination of a middle-end pass for metadata and an in-tree
back-end pass for analysis. Thanks to all for answering my questions!

William

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