[PATCH] D101806: [TargetLowering] Only inspect attributes in the arguments for ArgListEntry

Thu May 27 11:18:24 PDT 2021

aeubanks added a comment.

In D101806#2785168 <https://reviews.llvm.org/D101806#2785168>, @uweigand wrote:

> I looks like this patch, when committed as 1c7f32334d4becc725b9025fd32291a0e5729acd <https://reviews.llvm.org/rG1c7f32334d4becc725b9025fd32291a0e5729acd>, caused two additional build bot failures on s390x:
> https://lab.llvm.org/buildbot/#/builders/94/builds/3829
>  FAIL: libFuzzer:: msan.test
>  FAIL: libFuzzer:: swap-cmp.test
> This was unfortunately hidden by other failures at the time, so I didn't notice earlier.
>
> I see that https://reviews.llvm.org/D102667 was an attempt to fix problems with this patch for msan, but it addressed only the zeroext attribute.  On s390x we also often require the signext attribute, in particular for a plain "int" function argument or return value.  I have not looked into this in detail, but I see in msan_interface_internal.h quite a number of routines using "int", so it wouldn't surprise me if this could explain the regression ...

I may be misunderstanding your comment, but that patch added zeroext to parameters of msan runtime calls, it has nothing to do with handling of zeroext/signext of existing calls in the IR.

If this patch is actually causing an issue, either some instrumentation isn't properly setting ABI parameter attributes on calls that the instrumentation introduces (e.g. calls to runtime functions/intrinsics), or the frontend didn't properly handle ABI parameter attributes in the first place (which is unlikely for Clang due to indirect calls working for many years).

To debug the msan issue I saw, I diffed object files, then looked at the calls in the LLVM IR for differing functions to see if any of their parameter ABI attributes were mismatched with the callee's.

Since I don't have a s390x machine, I'm not sure how to debug the failures.

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