[llvm-dev] [RFC][FileCheck] New option to negate check patterns

Mon Feb 3 02:59:39 PST 2020

Thanks for the suggestions. I think the naming the whole line idea is okay,
but it feels a bit clunky. Either we'd have to have a syntax that FileCheck
would recognise without caring about the prefix (which seems to be against
the ethos of FileCheck, and also makes it less flexible), or in the case
I'm referring to, we'd have to have an extra line that does nothing other
than define the pattern that can then be used later, and we'd still have
some duplication (namely of the NOT check) i.e. something like:

RUN: tool --print-string | FileCheck %s --check-prefixes=COMMON,CHECK
RUN: tool --no-print-string | FileCheck %s --check-prefixes=COMMON,NO

COMMON-DEFINE-MYNAME: some string
CHECK: [[MYNAME]]
NO-NOT: [[MYNAME]]

Assuming we go with this modified proposal, I'd be tempted for something
like the above as the syntax, namely "<prefix>-DEFINE-<name of new
pattern>".

Perhaps a little less verbose, and more obvious could be the following:

CHECK-DEFINE: {{MYNAME:some string}}
or even
CHECK-DEFINE: {{VAR1:a literal}} {{VAR2:a.*pattern}}

Where "DEFINE" is a new kind of directive which says "don't actually match
anything, but do define regex patterns as defined on the line, so that they
can be used in subsequent checks". Patterns defined in this way would then
be applied in the same way as {{.*}} style patterns, unlike other
variables, which just match the earlier string they captured (ignoring
Thomas's recent changes at least).

On Fri, 31 Jan 2020 at 14:32, Robinson, Paul <paul.robinson at sony.com> wrote:

> Seems to me there was a proposal (possibly years ago now) to allow
> defining named patterns, from someone who had (IIRC) implemented such a
> feature in a downstream project.  I don’t remember the details of their
> use-case, but apparently by itself it wasn’t compelling enough to get the
> encouragement to proceed.
>
>
>
> FileCheck directives are already easy to get wrong, and adding a
> command-line option to change their interpretation just seems like asking
> for trouble. But adding a way to define a pattern that is independent of
> the input text seems like it could be useful.
>
>
>
> I’d suggest that initially at least, the define-a-pattern directive would
> take only “immediate” text, no embedded regexes. That is, you could do
>
>     DEFPAT[MYPATTERN]: Define a pattern here
>
> but you couldn’t do
>
>     DEFPAT[MYPATTERN]: Define {{some|any}} pattern here
>
> although it might be reasonable to allow
>
>     DEFPAT[PATTERN1]: some
>
>     DEFPAT[PATTERN2]: Define [[PATTERN1]] pattern here
>
> as the [[]] substitution can be done when the directive is read.
>
>
>
> My $.02,
>
> --paulr
>
>
>
> *From:* George Rimar <grimar at accesssoftek.com>
> *Sent:* Friday, January 31, 2020 5:52 AM
> *To:* Thomas Preud'homme <thomasp at graphcore.ai>; llvm-dev <
> llvm-dev at lists.llvm.org>; Robinson, Paul <paul.robinson at sony.com>;
> jh7370.2008 at my.bristol.ac.uk
> *Subject:* Re: [RFC][FileCheck] New option to negate check patterns
>
>
>
> Hi all,
>
>
>
> > I feel it might be confusing to have a CHECK becomes effectively a
> CHECK-NOT,
>
> > especially if the RUN line is far from the CHECK line (which is often
> the case when
>
> > a single RUN line drives several groups of CHECK directives (e.g. code
> generation
>
> > tested for several functions for a specific feature, like PIC). You also
> loose control
>
> > on where the NOT should be: it would have to be at the same location as
> the
>
> > CHECK even though for the NOT case you might want to check it somewhere
> else.
>
>
>
> I think I agree with Thomas.
>
> + the relationship with "CHECK-NOT/CHECK-NEXT/CHECK-SAME" might
> make things overcomplicated probably.
>
>
>
> > How about having a concept of regex variables where you give a name
>
> > to a given directive's pattern which you could reuse as another pattern.
> Something like (syntax TBD):
>
> >
>
> > CHECK<NAME>: mov [[REG:r[0-9]+]], #42
>
> > CHECK-NOT: <NAME>
>
>
>
> I.e. without adding a new optinons for FileCheck, something like the
> following?
>
> # RUN: llvm-sometool --print-string | FileCheck %s --check-prefix=CHECK1
>
> # RUN: llvm-sometool --no-print-string | FileCheck %s --check-prefix=
> CHECK2
>
>
>
> CHECK1<NAME>: mov [[REG:r[0-9]+]], #42
>
> CHECK2-NOT: <NAME>
>
>
>
> It might work probably.  We already have the ability to name parts of
>
> the output checked:
>
>
>
> // CHECK:      Dynamic Relocations {
>
> // CHECK-NEXT:   {{.*}} R_AARCH64_RELATIVE - [[BAR_ADDR:.*]]
>
>
>
> // CHECK:      Symbols [
>
> // CHECK-NEXT:     Value: [[BAR_ADDR]]
>
>
>
> So adding a way for naming the whole line does not look
>
> an unreasonable/inconsistent extention to me I think.
>
>
>
> Best regards,
>
> George | Developer | Access Softek, Inc
>
>
> ------------------------------
>
> *From:* James Henderson <jh7370.2008 at my.bristol.ac.uk>
> *Sent:* 31 January 2020 09:14
> *To:* llvm-dev <llvm-dev at lists.llvm.org>; Thomas Preud'homme <
> thomasp at graphcore.ai>; Paul Robinson <paul.robinson at sony.com>; George
> Rimar <grimar at accesssoftek.com>
> *Subject:* [RFC][FileCheck] New option to negate check patterns
>
>
>
>      [This message was sent from somebody outside of your organisation]
>
>
>
>
> Hi all,
>
>
>
> There have been a few cases recently where I've noticed two test cases in
> the same lit test that do the same thing except invert the CHECK, to show
> that something is NOT present. I'm talking about something like the
> following:
>
>
>
> # RUN: llvm-sometool --print-string | FileCheck %s --check-prefix=STRING
>
> # RUN: llvm-sometool --no-print-string | FileCheck %s
> --check-prefix=NO-STRING
>
> # STRING: This is the string
>
> # NO-STRING-NOT: This is the string
>
>
>
> In such cases, as can be seen, the CHECK line effectively has to be
> duplicated (either in an explicit check like in the above example, or via
> --implicit-check-not). Duplication is generally bad, especially in this
> sort of case, as it only takes a typo in the NOT pattern, or a careless
> developer/reviewer pair changing the output to cause the NOT pattern to no
> longer be useful.
>
>
>
> I'd like to propose a new FileCheck option (e.g.
> --check-not-prefix/--check-not-prefixes) which allows implicitly converting
> a check prefix to a -NOT version of the same prefix. That would allow
> writing the above example as:
>
>
>
> # RUN: llvm-sometool --print-string | FileCheck %s --check-prefix=STRING
>
> # RUN: llvm-sometool --no-print-string | FileCheck %s
> --check-not-prefix=STRING
>
> # STRING: This is the string
>
>
>
> If there was a typo or somebody changed the string output, this mechanism
> would ensure there is no chance of the pattern rotting.
>
>
>
> Caveat: I don't know what would be the appropriate way of handling
> non-trivial checks, i.e. existing CHECK-NOT/CHECK-NEXT/CHECK-SAME etc. I'd
> appreciate any ideas on this.
>
>
>
> Thoughts?
>
>
>
> James
>
>
>
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