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

[Stephen Lin]

Thanks Owen; Andy (Trick) off-list says he thinks it's a good idea, too.

Eli B. (also off-list) thinks that the documentation can be approved
and also suggests that the name CHECK-BOUNDARY is better. Anyone else
have an opinion?

I much prefer CHECK-LABEL to CHECK-BOUNDARY myself, but I am willing
to paint the bike shed whatever color others can agree on.

Stephen

On Thu, Jul 11, 2013 at 12:31 PM, Owen Anderson <resistor at mac.com> wrote:
> I'm not familiar enough with the FileCheck internals to comment on the implementation, but I *really* like this feature.  I've spent way too much time over the years tracking down cryptic FileCheck errors that would have been solved by this.
>
> --Owen
>
> On Jul 11, 2013, at 10:50 AM, Stephen Lin <swlin at post.harvard.edu> wrote:
>
>> Hi,
>>
>> Can anyone review this patch? It adds a new directive type called
>> "CHECK-LABEL" to FileCheck...
>>
>> 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.
>>
>> As an example, I purposely introduced the a switch fall-through bug in
>> the last patch I submitted to llvm-commits ("Allow FMAs in safe math
>> mode in some cases when one operand of the fmul is either exactly 0.0
>> or exactly 1.0")...
>>
>> Bug diff:
>>
>> diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>> b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>> index 0290afc..239b119 100644
>> --- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>> +++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>> @@ -5791,7 +5791,7 @@ static bool isExactlyZeroOrOne(const
>> TargetLowering &TLI, const SDValue &Op) {
>>           continue;
>>         }
>>       }
>> -      break;
>> +//      break;
>>     case ISD::FADD:
>>       if (ConstantFPSDNode *V0CFP =
>>             dyn_cast<ConstantFPSDNode>(V->getOperand(0))) {
>>
>> The single error message without CHECK-LABEL is:
>>
>> ; CHECK-SAFE: test_add_8
>>              ^
>> <stdin>:125:2: note: scanning from here
>> .cfi_endproc
>> ^
>> <stdin>:127:10: note: possible intended match here
>> .globl _test_add_10
>>         ^
>>
>> The error messages with CHECK-LABEL are:
>>
>> ; CHECK-SAFE: vmulsd
>>              ^
>> <stdin>:87:2: note: scanning from here
>> .align 4, 0x90
>> ^
>> <stdin>:95:2: note: possible intended match here
>> vsubsd %xmm0, %xmm3, %xmm0
>> ^
>> fp-contract.ll:118:15: error: expected string not found in input
>> ; CHECK-SAFE: vmulsd
>>              ^
>> <stdin>:102:2: note: scanning from here
>> .align 4, 0x90
>> ^
>> <stdin>:109:2: note: possible intended match here
>> vsubsd %xmm2, %xmm3, %xmm2
>> ^
>> fp-contract.ll:288:15: error: expected string not found in input
>> ; CHECK-SAFE: vmulsd
>>              ^
>> <stdin>:258:2: note: scanning from here
>> .align 4, 0x90
>> ^
>> <stdin>:266:2: note: possible intended match here
>> vsubsd %xmm0, %xmm3, %xmm0
>> ^
>>
>> The three error messages in the CHECK-LABEL case exactly pinpoint the
>> source lines of the actual problem in three separate blocks; the
>> single error message given without CHECK-LABEL is (imho) much less
>> useful.
>>
>> (In this case, the non-CHECK-LABEL version happens to error on the on
>> a label line, so the user could presume that the error happened in the
>> block immediately before test_add_8, which is correct, but in general
>> this might not be true; the only thing that can be concluded is that
>> the error happened sometime before test_add_8.)
>>
>> Please let me know if you have any feedback.
>>
>> Stephen
>>
>> ---------- Forwarded message ----------
>> From: Stephen Lin <swlin at apple.com>
>> Date: Mon, Jun 10, 2013 at 4:21 PM
>> Subject: [PATCH] Add CHECK-LABEL directive to FileCheck to allow more
>> accurate error messages and error recovery
>> To: llvm-commits at cs.uiuc.edu
>>
>>
>> Actually, I went ahead and renamed it CHECK-LABEL and rebased, since I
>> think it’s better :)
>> -Stephen
>> <check-label.patch>_______________________________________________
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>> llvm-commits at cs.uiuc.edu
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>
>
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