[PATCH] D35384: PGOInstrumentation: Move profile matching warnings to remarks

[Chandler Carruth via llvm-commits]

On Thu, Jul 13, 2017 at 7:29 PM Xinliang David Li via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> On Thu, Jul 13, 2017 at 4:17 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>>
>>
>> On Thu, Jul 13, 2017 at 2:03 PM David Li via Phabricator <
>> reviews at reviews.llvm.org> wrote:
>>
>>> davidxl added a comment.
>>>
>>> Blindly downgrade the warning into remarks can be bad -- profile
>>> mismatch problems can go undetected. People may spend more time diagnosing
>>> performance regressions due to missed warnings. Worse, we may regress in
>>> compiler without noticing.
>>>
>>
>> Any other ideas?
>>
>> The diagnostic handling callbacks through to Clang aren't granular enough
>> to demote only this warning to -Wno-error
>>
>
> Can this be fixed?
>
>
>
>> (also as a warning it undermines the confidence as warnings as actionable
>> things that Clang has helped provide users).
>>
>
>
> Warnings like this are usually actionable by users or compiler developers.
>

Warnings are really to indicate a bug in user code.

For example, we use some things like this to warn users when inline
assembly is likely to have a bug, because that is user code that can be
fixed.

A profile mismatch seems much less like "user code has a bug" and so
doesn't seem to fit any well in the "warning" category.

On the other hand, remarks were specifically designed to be non-bug
important information from optimization passes that users may need to act
on.
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