[Patch][LoopVectorize] Print vectorization analysis when loop hint pragma is specified

[Hal Finkel via llvm-commits]

Hi Tyler,

Thanks for working on this!

+    // If a loop hint is provided the diagnostic is always produced.
+    const char *name = Hints.isForced() ? DiagnosticInfo::AlwaysPrint : LV_NAME;

name -> Name

These LGTM.

P.S. I assume we should add similar logic to the loop unroller (please add a FIXME if you're not going to do this yourself). Another place where this would be useful is to warn the user when a function marked always_inline is not actually inlined.

 -Hal

----- Original Message -----
> From: "Tyler Nowicki" <tnowicki at apple.com>
> To: "Gonzalo BG" <gonzalobg88 at gmail.com>, "Hal J. Finkel" <hfinkel at anl.gov>, "Commit Messages and Patches for LLVM"
> <llvm-commits at lists.llvm.org>, "llvm cfe" <cfe-commits at lists.llvm.org>
> Cc: "Gerolf Hoflehner" <ghoflehner at apple.com>
> Sent: Friday, August 7, 2015 4:15:51 PM
> Subject: [Patch][LoopVectorize] Print vectorization analysis when loop hint pragma is specified
> 
> 
> Hi,
> 
> 
> 
> 
> 
> Currently, when loop hint is used but vectorization fails we generate
> a warning. To get the analysis the user needs to provide the command
> line option -Rpass-analysis=<passname> with the correct pass name.
> BUT we don’t tell the user which pass name they will need to get the
> analysis message. We should be displaying the analysis without
> having to request it.
> 
> 
> These patches print the analysis information when vectorization fails
> on loops with hints when the compiler option ‘-Rpass-analysis’ is
> provided without ‘=<passname>'. Users of loop hints can provide the
> compiler option with their regular debug builds to ensure they
> always get the analysis when vectorization fails. This approach is
> preferred because diagnostic printing needs line number tracking
> which is not enabled by normally. Specifying the option without a
> pass-target enables line number tracking and makes viewing the
> messages optional.
> 
> 
> The LLVM patches modify the pass-name of the diagnostic to
> DiagnosticInfo::AlwaysPrint, which is an empty const char*. The use
> of DiagnosticInfo::AlwaysPrint is recognized when filtering the
> diagnostics allowing the message to be printed even if the filter
> doesn’t match. Note that the analysis of loops with hints will
> always be printed whenever the compiler option is provided even if
> ‘=<pass name>' is specified. This allows both types of analyses to
> be printed at the same time rather than hiding the analysis on loops
> with hints with an pass-target is given.
> 
> 
> *These patches build on several previous patches still in review to
> add late-diagnostics for fp-commut and aliasing. See threads ' Late
> evaluation of vectorization r equirements’ and ' Late evaluate of
> runtime pointer check's threshold' .
> 
> 
> Comments and reviews are much appreciated!
> 
> 
> Tyler
> 
> 
> (sorry if you received this twice. I used the wrong mailing list
> addresses)
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory