[LLVMdev] [RFC] Add warning capabilities in LLVM.

[Quentin Colombet]

Hi Paul,

Thanks for sharing your patches.

This is interesting.

Cheers,

-Quentin

On Jul 29, 2013, at 2:40 PM, Redmond, Paul <paul.redmond at intel.com> wrote:

> Hi,
> 
> Several weeks ago a prototyped a feature similar to what you're describing. I was experimenting to see how one might implement a feature like ICC's -vec–report feature in clang/llvm. My approach was to create an ImmutablePass which stores notes. I modified the loop vectorizer and the unroll pass to add notes when loops were vectorized or unrolled.
> 
> On the clang side I add an OptReport to the pass manager and dump out the notes as diagnostics. It worked ok as a prototype but getting the source locations correct was a bit fragile.
> 
> I've attached some patches in case you're interested.
> 
> Paul
> 
> 
> 
> From: Quentin Colombet <qcolombet at apple.com<mailto:qcolombet at apple.com>>
> Date: Tuesday, 16 July, 2013 8:21 PM
> To: LLVM Developers Mailing List <llvmdev at cs.uiuc.edu<mailto:llvmdev at cs.uiuc.edu>>
> Subject: [LLVMdev] [RFC] Add warning capabilities in LLVM.
> 
> Hi,
> 
> I would like to start a discussion about error/warning reporting in LLVM and how we can extend the current mechanism to take advantage of clang capabilities.
> 
> 
> ** Motivation **
> 
> Currently LLVM provides a way to report error either directly (print to stderr) or by using a user defined error handler. For instance, in inline asm parsing, we can specify the diagnostic handler to report the errors in clang.
> 
> The basic idea would be to be able to do that for warnings too (and for other kind of errors?).
> A motivating example can be found with the following link where we want LLVM to be able to warn on the stack size to help developing kernels:
> http://llvm.org/bugs/show_bug.cgi?id=4072
> 
> By adding this capability, we would be able to have access to all the nice features clang provides with warnings:
> - Promote it to an error.
> - Ignore it.
> 
> 
> ** Challenge **
> 
> To be able to take advantage of clang framework for warning/error reporting, warnings have to be associated with warning groups.
> Thus, we need a way for the backend to specify a front-end warning type.
> 
> The challenge is, AFAICT (which is not much, I admit), that front-end warning types are statically handled using tablegen representation.
> 
> 
> ** Advices Needed **
> 
> 1. Decide whether or not we want such capabilities (if we do not we may just add sporadically the support for a new warning/group of warning/error).
> 2. Come up with a plan to implement that (assuming we want it).
> 
> 
> Thanks for the feedbacks.
> 
> Cheers,
> 
> -Quentin
> 
> <opt_report_clang.diff><opt_report_llvm.diff>

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