[llvm-dev] Passing arguments to LLVM pass through Clang

Shishir V Jessu via llvm-dev llvm-dev at lists.llvm.org
Tue Mar 17 11:22:11 PDT 2020

Hi Benno,

Thanks for your response! Unfortunately, I don't think the -mllvm flag is
doing what I need.

Specifically, I am adding to the LowerTypeTests optimization pass in LLVM.
When I invoke this pass with opt, there is a command line option called "
lowertypetests-read-summary", which allows me to specify a file name. I've
added a similar option, that takes a filename as input and opens that file
to obtain some information necessary to do the pass.

It looks like -lowertypetests is not a pass that -mllvm recognizes, so I'm
not able to input arguments to this pass using -mllvm. In fact, it doesn't
seem like *any* of the passes that -mllvm recognizes can be invoked
with opt. Do
you know if there's some code I can modify that will allow -mllvm to
recognize this pass? Or is there a better way to get clang to send the
filename input to my pass? Thanks so much for your help!

Shishir Jessu

On Tue, Mar 17, 2020 at 2:48 AM Benno Krauss <benno.krauss at wibu.com> wrote:

> Hello Shishir,
> To pass arguments to LLVM from clang, use something like `clang source.c
> -mllvm -customarg -mllvm argvalue`. The -mllvm argument tells clang to
> forward the following argument to LLVM. Similarly, there is the -Xclang
> argument to pass the following argument to clang proper, as opposed to the
> clang driver.
> Cheers,
> Benno
> Am 16.03.2020 um 23:45 schrieb Shishir V Jessu via llvm-dev <
> llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>:
> Hello,
> I am adding to an LLVM pass that requires a filename as input. I am able
> to input this filename as a command line argument when I invoke this pass
> using opt, but I ultimately need to pass this argument to my code when I
> compile code with clang.
> How can I pass this argument to clang so that I can use it in my LLVM
> pass? Thanks for your help!
> Best,
> Shishir Jessu
> [
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