[llvm-dev] [clang] Running a single testcase

[Brian Cain via llvm-dev]

On Mon, May 7, 2018 at 10:46 AM, Sedat Dilek <sedat.dilek at gmail.com> wrote:

> On Mon, May 7, 2018 at 5:19 PM, Brian Cain <brian.cain at gmail.com> wrote:
> >
> >
> ...




> >  Can you give a little more context?  What is your ultimate goal for this
> > activity?  Why would you want to run the test in this fashion and what
> > meaning would you attribute to the test passing or failing?
> >
>
> When compiling a Linux-kernel I hit a problem in the
> KVM/paravirtualization area and "clobbering RCX" on Debian/testing
> AMD64.
> The question came up, is this is a compiler bug or not.
> Details see [1].
>
> Thus, I was looking for a reproducible testcase.
> I have seen that clang ships some tests.
> So, I was curious to run a single one.
> Not sure if clang/test/Sema/asm.c is suitable here to see "clobbering
> RCX" on Debian/x86-64.
>
>
Yes, I agree that it might not be the right test.


> On my host I have installed a clang-7 package from <apt.llvm.org>.
> I wanted to test against that version.
>
> Does this help you?
>
> - Sedat -
>
> [1] https://lkml.org/lkml/2018/4/24/1227
>

I see, yes, this is clearer now.

IIUC, this test is testing clang's behavior regarding inline assembly and
probably won't verify things like which registers are saved and restored.

I think you might get resolution on this issue faster if you reduce
native_save_fl()
and its caller to a simple example that shows RCX not being saved.  Bonus
points if you can identify any conditions that change this behavior -- or
versions of clang that behave differently.  Then share your test and ask on
llvm-dev and/or cfe-dev whether or not this behavior is expected.

-- 
-Brian
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