[PATCH] Add CHECK-UNIQ directive to FileCheck to allow more accurate error messages and error recovery

[Reid Kleckner]

If this only affects error messages, could we simply teach FileCheck some
heuristics for bounding the region of the intended match, based on common
patterns like 'CHECK: define ...', 'CHECK: asdf:', or 'CHECK: }' ?


On Wed, May 29, 2013 at 1:51 PM, Stephen Lin <swlin at post.harvard.edu> wrote:

> Anyone have any thoughts on this? :)
> -Stephen
>
> ---------- Forwarded message ----------
> From: Stephen Lin <swlin at post.harvard.edu>
> Date: Sat, May 18, 2013 at 5:36 PM
> Subject: [PATCH] Add CHECK-UNIQ directive to FileCheck to allow more
> accurate error messages and error recovery
> To: llvm-commits at cs.uiuc.edu
> Cc: Eli Bendersky <eliben at google.com>
>
>
> Hi,
>
> This patch adds a new directive, CHECK-UNIQ, which is meant to be used
> to match unique identifier lines (like labels).
>
> If present in a match file, FileCheck will use these directives to
> split the input into blocks that are independently processed, ensuring
> that a CHECK does not inadvertently match a line in a different block
> (which can lead to a misleading/useless error message when the error
> is eventually caught). Also, FileCheck can now recover from errors
> within blocks by continuing to the next block.
>
> Please let me know if you have any comments or suggestions.
>
> Also, if people like this idea, I will also script a mass update of
> tests to use CHECK-UNIQ in common cases, like assembly labels and IR
> function definition lines. (I will include a sanity check to make sure
> each pattern does indeed uniquely match a single line of the input
> before updating.)
>
> Stephen
>
> ---------- Forwarded message ----------
> From: Eli Bendersky <eliben at google.com>
> Date: Thu, Apr 25, 2013 at 10:37 AM
> Subject: Re: [LLVMdev] Minor FileCheck proposal: CHECK-UNIQUE for
> labels to improve error messages
> To: Stephen Lin <swlin at post.harvard.edu>
> Cc: llvmdev <LLVMdev at cs.uiuc.edu>
>
>
> On Wed, Apr 24, 2013 at 8:05 PM, Stephen Lin <swlin at post.harvard.edu>
> wrote:
> >
> > Hi,
> >
> > Apologies if this has been proposed before; I couldn't find anything
> > in basic searching.
> >
> > I've been writing tests lately and noticed that the error messages are
> > not very helpful in cases where a check is incorrect but matches
> > something that occurs in a later block: the checker continues assuming
> > that the matched line is correct (no matter how much farther ahead it
> > occurs) and then provides a misleading error message some time later.
> >
> > The problem is exacerbated if many similar tests are put in one file,
> > since many checks can end up succeeding with unintended matches before
> > something ends up failing.
> >
> > I propose a simple addition to FileCheck syntax to improve error
> > messages in this case: a CHECK-UNIQUE directive which indicates that a
> > given check is a unique match that should only occur once (and only
> > once) in a given file and can only be matched with the given
> > CHECK-UNIQUE; this would be used for labels or any other unique
> > identifier lines.
> >
> > The CHECK-UNIQUE lines can then allow a better error message to be
> > produced, by basically treating each section between CHECK-UNIQUE
> > lines separately, so the actual line causing the error can be
> > pinpointed more accurately.
> >
> > Anyone else thing this is a good idea? I'm happy to work on this if so.
>
>
> I like this idea. There are many places in the test cases where this
> idiom is needed and currently CHECK followed by a CHECK-NOT is used,
> which is cumbersome.
>
> Eli
>
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