[llvm-dev] [FileCheck] Error for unused check prefixes (was: [RFC] FileCheck: (dis)allowing unused prefixes)

via llvm-dev llvm-dev at lists.llvm.org
Wed Feb 3 06:46:40 PST 2021 

Agreed, in particular this half of the catching-typos problem is definitely worth solving.
(The other half would be typos in the CHECK directives themselves, which is a distinctly harder problem and one that FileCheck cannot solve on its own.)
--paulr

From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of James Henderson via llvm-dev
Sent: Wednesday, February 3, 2021 3:58 AM
To: Fāng-ruì Sòng <maskray at google.com>
Cc: LLVM Dev <llvm-dev at lists.llvm.org>; Johannes Doerfert <jdoerfert at anl.gov>
Subject: Re: [llvm-dev] [FileCheck] Error for unused check prefixes (was: [RFC] FileCheck: (dis)allowing unused prefixes)

In my opinion, the cost of a bit of inconvenience for users who want to allow unused prefixes is far outweighed by the potential to catch bugs (both test bugs and more importantly genuine bugs hidden by test bugs), so +1 to the default being false for the option.

On Tue, 2 Feb 2021 at 23:50, Fāng-ruì Sòng <maskray at google.com<mailto:maskray at google.com>> wrote:
Last October Mircea sent an RFC about (dis)allowing unused check prefixes in FileCheck: https://lists.llvm.org/pipermail/llvm-dev/2020-October/146162.html<https://urldefense.com/v3/__https:/lists.llvm.org/pipermail/llvm-dev/2020-October/146162.html__;!!JmoZiZGBv3RvKRSx!urdK8m31QsturtRGthDVgFi6Io__zthaWkM1QVuByejXzSHlgkB44SvRajFZNt1pFQ$>
(In short, if FileCheck --check-prefix or --check-prefixes specifies a prefix which does not occur in the test, FileCheck will error. Note: a `-NOT` pattern is also counted as an occurrence.)

Mircea created a worksheet https://docs.google.com/spreadsheets/d/1o6q3XH1n3DDyyccnYZ_kVfhFbTDzC_S09e973_cwYuw/edit#gid=0<https://urldefense.com/v3/__https:/docs.google.com/spreadsheets/d/1o6q3XH1n3DDyyccnYZ_kVfhFbTDzC_S09e973_cwYuw/edit*gid=0__;Iw!!JmoZiZGBv3RvKRSx!urdK8m31QsturtRGthDVgFi6Io__zthaWkM1QVuByejXzSHlgkB44SvRajHvvJddRQ$> which may be a bit stale now but llvm-project has reached a state where all issues have been identified and fixed, or worked around (by opting in FileCheck --allow-unused-prefixes in some test directories, such as: clang/test/OpenMP, llvm/test/Transforms/Attributor and llvm/test/FileCheck).

We can make a switch if the community thinks that not allowing unused prefixes is the better default: https://reviews.llvm.org/D95849<https://urldefense.com/v3/__https:/reviews.llvm.org/D95849__;!!JmoZiZGBv3RvKRSx!urdK8m31QsturtRGthDVgFi6Io__zthaWkM1QVuByejXzSHlgkB44SvRajH7eqwn6Q$>
For downstream projects using FileCheck and lit, it should be easy to restore the previous permissive behavior


from lit.llvm.subst import ToolSubst



fc = ToolSubst('FileCheck', unresolved='fatal')

config.substitutions.insert(0, (fc.regex, 'FileCheck --allow-unused-prefixes'))

# Note: if multiple --allow-unused-prefixes options are specified, the last wins.

Personally I am strongly in favor of disallowing unused check prefixes by default. We have identified numerous issues:

(1) typo. A misspelled check prefix does not test what it intends to test.
(2) bitrot tests due to refactoring
(3) unspecified `-NOT` patterns. Sometimes a test uses something like `--check-prefixes=COMMON,TRUE` and `--check-prefixes=COMMON,FALSE` to test both behaviors but they forget to include a `FALSE-NO:` pattern to test that some string does not appear.

(1) and (2) are especially common. There are indeed tests where --allow-unused-prefixes is more suitable - but they are sufficiently few that I think the default should be --allow-unused-prefixes=false.

So, what do folks think?

On Mon, Nov 16, 2020 at 8:22 AM Mircea Trofin <mtrofin at google.com<mailto:mtrofin at google.com>> wrote:
Thanks for doing this (as well as the awesome cleanup in CodeGen/X86)!

On Sun, Nov 15, 2020 at 6:31 PM Wang, Pengfei <pengfei.wang at intel.com<mailto:pengfei.wang at intel.com>> wrote:
Hi,

I wrote a script to help removing unused trivial prefixes. It is located in llvm/utils/update_test_prefix.py.
It is a rough one and based on problems I met. It also highly relies on the output of llvm-lit and update tools. So carefully verification on its changes is MUST.

Here's the usage of it:
1. turn allow-unused-prefixes to false and built it: sed -i '/allow-unused-prefixes/s/true/false/' llvm/utils/FileCheck/FileCheck.cpp;
2. cd llvm-project;
3. make sure llvm-lit and update_llc_test_checks.py or other update tools are available;
4. llvm/utils/update_test_prefix.py test_file_you_want_to_update.xxx
5. you can also put them in a file and cat update_tests.txt | xargs llvm/utils/update_test_prefix.py

The script removes unused prefixes and verifies those autogenerated tests. It reports "Failed" if there's conflicting in regeneration and "Changed" if there're changes in the check contents. There's a known issue if the prefix is not connected by "=", e.g. "--check-prefix X86". It will be put into "Aborted". Please pay attention for tests in these lists.
Wish the script would help you😊

Thanks
Pengfei

-----Original Message-----
From: Fāng-ruì Sòng <maskray at google.com<mailto:maskray at google.com>>
Sent: Friday, November 6, 2020 3:50 AM
To: Matt Arsenault <Matthew.Arsenault at amd.com<mailto:Matthew.Arsenault at amd.com>>; Alexey.Bataev at ibm.com<mailto:Alexey.Bataev at ibm.com>; Tim Northover <t.p.northover at gmail.com<mailto:t.p.northover at gmail.com>>; Wang, Pengfei <pengfei.wang at intel.com<mailto:pengfei.wang at intel.com>>
Cc: Mircea Trofin <mtrofin at google.com<mailto:mtrofin at google.com>>; David Blaikie <dblaikie at gmail.com<mailto:dblaikie at gmail.com>>; LLVM Dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>>
Subject: Re: [llvm-dev] [RFC] FileCheck: (dis)allowing unused prefixes

On Thu, Nov 5, 2020 at 11:36 AM David Blaikie via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
>
>
>
> On Thu, Nov 5, 2020 at 10:46 AM Mircea Trofin <mtrofin at google.com<mailto:mtrofin at google.com>> wrote:
>>
>>
>>
>> On Thu, Nov 5, 2020 at 10:40 AM David Blaikie <dblaikie at gmail.com<mailto:dblaikie at gmail.com>> wrote:
>>>
>>>
>>>
>>> On Thu, Nov 5, 2020 at 7:30 AM Mircea Trofin via llvm-dev <llvm-dev at lists.llvm.org<mailto:llvm-dev at lists.llvm.org>> wrote:
>>>>
>>>> There are currently 1350 owner-less failures in the spreadsheet. These seem to be the larger areas there.
>>>>
>>>> If you see an area you have ownership or expertise in, please sign up for fixing the tests by Monday, Nov. 9.
>>>>
>>>> Otherwise, I will "blanket-add" --allow-unused-prefixes=true to the remaining failing tests.
>>>
>>>
>>> If/when you do that, probably worth adding a comment at each site to clarify that this was added automatically, not vetted/intentionally added by a human. Something like "// FIXME: Verify that unused prefixes are used intentionally" or the like.
>>
>> Ack. or, we can grep for -allow-unused-prefixes=true, wdyt?
>
>
> Not sure I understand who/when<https://urldefense.com/v3/__https:/teams.googleplex.com/u/when__;!!JmoZiZGBv3RvKRSx!urdK8m31QsturtRGthDVgFi6Io__zthaWkM1QVuByejXzSHlgkB44SvRajGainn1NQ$> they would grep for that?
>
> I was suggesting adding an explicit "this use of --allow-unused-prefixes=true hasn't been confirmed as intentional" so that the backwards compatibility cases can be distinguished from the intentional cases when someone is reading the test case, rather than puzzling over why this flag was added (which looks intentional) though the unused prefix may not make sense in that particular test. It'll make it easier in the future when someone does look at the test for them to not feel like they're being implicitly told "this use of unused prefixes is intentional" (by the presence of an explicit flag requesting such support) while staring at the test and not being able to see why someone would've done that intentionally.

Directly CCing some folks who can fix or find people to fix some directories (*/AMDGPU, */X86, */OpenMP, */AArch64) on
https://docs.google.com/spreadsheets/d/1o6q3XH1n3DDyyccnYZ_kVfhFbTDzC_S09e973_cwYuw/edit#gid=0<https://urldefense.com/v3/__https:/docs.google.com/spreadsheets/d/1o6q3XH1n3DDyyccnYZ_kVfhFbTDzC_S09e973_cwYuw/edit*gid=0__;Iw!!JmoZiZGBv3RvKRSx!urdK8m31QsturtRGthDVgFi6Io__zthaWkM1QVuByejXzSHlgkB44SvRajHvvJddRQ$>
After these big directories are cleaned up, the remaining tests should be manageable in amount.

How to reproduce:

sed -i '/allow-unused-prefixes/s/true/false/' llvm/utils/FileCheck/FileCheck.cpp
git update-index --assume-unchanged llvm/utils/FileCheck/FileCheck.cpp
ninja check-llvm   # or check-clang ...




>>>
>>>
>>>>
>>>>
>>>>
>>>> On Fri, Oct 30, 2020 at 12:48 PM Mircea Trofin <mtrofin at google.com<mailto:mtrofin at google.com>> wrote:
>>>>>
>>>>> An update: as of 871d658c9ceb, the flag is now available, if folks need to use it.
>>>>>
>>>>> On Thu, Oct 29, 2020 at 10:28 AM Mircea Trofin <mtrofin at google.com<mailto:mtrofin at google.com>> wrote:
>>>>>>
>>>>>> Hello all,
>>>>>>
>>>>>> TL;DR; if you used FileCheck --check-prefixes and you missed (misspelled, for instance) one of the prefixes in your test, FileCheck silently ignores that and the test passes.
>>>>>>
>>>>>> 1579 tests have this property.
>>>>>>
>>>>>>
>>>>>> The details
>>>>>> =========
>>>>>> Please refer to https://reviews.llvm.org/D90281<https://urldefense.com/v3/__https:/reviews.llvm.org/D90281__;!!JmoZiZGBv3RvKRSx!urdK8m31QsturtRGthDVgFi6Io__zthaWkM1QVuByejXzSHlgkB44SvRajEFjOdqmg$> and the
>>>>>> discussion there for more details (make sure you open "older
>>>>>> changes" for full context)
>>>>>>
>>>>>> The problem is covered by the TL;DR;.
>>>>>>
>>>>>> The proposal is to add an explicit flag to FileCheck, --allow-unused-prefixes, to indicate whether the current behavior is intended (for instance, jdoerfert contributed a scenario where that is the case).
>>>>>>
>>>>>> We want the default behavior to be 'strict', i.e. --allow-unused-prefixes=false. Doing that right now would lead to 1500 test failures.
>>>>>>
>>>>>> To get there (thanks, maskray, for suggestion), we propose we:
>>>>>> * land D90281 where the flag is introduced, but is flipped to
>>>>>> match today's behavior
>>>>>> * employ a 'busy beavers' approach, where test maintainers patch their tests:
>>>>>>   - either leveraging the flag, to explicitly indicate that unused prefixes is intended (i.e. add --allow-unused-patches=true); or
>>>>>>   - fix the test (e.g. maybe there was a misspelling issue/omission/etc).
>>>>>>
>>>>>> A spreadsheet with the failing tests is available here [1].
>>>>>>
>>>>>> The request to the community members is to please sign up for their respective area in the spreadsheet, and then mark it completed when that's the case (yes/no in the respective column).
>>>>>>
>>>>>> When all the tests are fixed, we will then flip --allow-unused-prefixes to false by default.
>>>>>>
>>>>>> Meanwhile, please consider leveraging the flag explicitly when you author new tests that use --check-prefixes. That can be then cleaned up easily after we switch to the 'strict' behavior.
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>> [1]
>>>>>> https://docs.google.com/spreadsheets/d/1o6q3XH1n3DDyyccnYZ_kVfhFb<https://urldefense.com/v3/__https:/docs.google.com/spreadsheets/d/1o6q3XH1n3DDyyccnYZ_kVfhFb__;!!JmoZiZGBv3RvKRSx!urdK8m31QsturtRGthDVgFi6Io__zthaWkM1QVuByejXzSHlgkB44SvRajGTcy--8Q$>
>>>>>> TDzC_S09e973_cwYuw/edit?usp=sharing
>>>>
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