llvm dev - Nov 2021 - Strip IR metadata information in a unit test

Thanks for the pointer!

I'm a little confused how the custom script (specified by --test arg
<https://github.com/llvm-mirror/llvm/blob/master/tools/llvm-reduce/llvm-reduce.cpp#L38>)
tells llvm-reduce if something is interesting in the IR.

Is it a common practice to wrap "llvm-lit <IR>" into a shell
script to
simplify IR for a unit test?

On Thu, Nov 18, 2021 at 9:23 AM Philip Reames <listmail at
philipreames.com>
wrote:
> See llvm-reduce.
>
> Philip
> On 11/18/21 9:14 AM, Mingming Liu via llvm-dev wrote:
>
> Hi,
>
>     When modifying IR for the purpose of a unit test (e.g., in
> https://github.com/llvm/llvm-project/tree/main/llvm/test/Transforms/SROA),
> the IR generated by OPT may have metadata that's not used by the tested
> pass.
>
>     Are there some general suggestions on how to strip metadata? Is this
> mostly empirical by analyzing how the metadata takes effect in the e2e
> compiling process (i.e., outside of one pass)? Any form of pointers /
> related threads in the past would be enlightening!
>
>      From this perspective stripping unused metadata manually could be
> error prone (e.g., for a more complex IR, or a test IR consisting of 10+
> functions).
>
> --
> Thanks,
> Mingming
>
> _______________________________________________
> LLVM Developers mailing listllvm-dev at
lists.llvm.orghttps://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
-- 
Thanks,
Mingming
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Am Do., 18. Nov. 2021 um 12:34 Uhr schrieb Mingming Liu via llvm-dev
<llvm-dev at lists.llvm.org>:
> I'm a little confused how the custom script (specified by --test arg)
tells llvm-reduce if something is interesting in the IR.
>
> Is it a common practice to wrap "llvm-lit <IR>" into a
shell script to simplify IR for a unit test?
Yes, it is expected that you write your own "interesting-ness" script.
However I don't think you can use llvm-lit (which requires a `RUN:`
command comment in the file that llvm-reduce does not emit). Instead,
take the command that llvm-lit would execute (Execute with -v flag)
and instead of the test file (%s in the `RUN: ` command), pass $1 to
the opt/llc executable within your script. Check whether it has failed
with `%?`.

Michael