r215360 - Increase SmallVector<> size in DiagnosticsEngine::setSeverityForGroup

[Hans Wennborg]

On Mon, Aug 11, 2014 at 1:28 PM, David Blaikie <dblaikie at gmail.com> wrote:
> On Mon, Aug 11, 2014 at 9:05 AM, Hans Wennborg <hans at hanshq.net> wrote:
>> Author: hans
>> Date: Mon Aug 11 11:05:54 2014
>> New Revision: 215360
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=215360&view=rev
>> Log:
>> Increase SmallVector<> size in DiagnosticsEngine::setSeverityForGroup
>>
>> In a Clang bootstrap, this vector always held 129 elements.
>
> Presumably this is because the largest diagnostic group has 129
> elements. When you say "always held 129 elements" - you mean the
> maximum for a given compilation was 129? Or on /every/ call it was
> 129? I'd be surprised if it was the same count on every call.

It was 129 on every call. Maybe it was only getting called for a
specific diagnostics group.

> & are we going to update this whenever the number of diagnostics in
> the largest group changes?

I bumped it to 256 thinking that that "should be enough for everyone".

> (& my personal leaning being "if performance here doesn't matter,
> perhaps we should have a default size or drop the small optimization
> entirely so we don't have to wonder if it's right/needs updating in
> the future")

I got samples from about 2000 small-optimized containers in my
bootstrap. The vast majority of those are probably not important for
performance, but if we switched all of them to non-small optimized
containers I'm sure the impact would be visible.

 - Hans

>> Modified: cfe/trunk/lib/Basic/Diagnostic.cpp
>> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Basic/Diagnostic.cpp?rev=215360&r1=215359&r2=215360&view=diff
>> ==============================================================================
>> --- cfe/trunk/lib/Basic/Diagnostic.cpp (original)
>> +++ cfe/trunk/lib/Basic/Diagnostic.cpp Mon Aug 11 11:05:54 2014
>> @@ -232,13 +232,13 @@ bool DiagnosticsEngine::setSeverityForGr
>>                                              StringRef Group, diag::Severity Map,
>>                                              SourceLocation Loc) {
>>    // Get the diagnostics in this group.
>> -  SmallVector<diag::kind, 8> GroupDiags;
>> +  SmallVector<diag::kind, 256> GroupDiags;
>>    if (Diags->getDiagnosticsInGroup(Flavor, Group, GroupDiags))
>>      return true;
>>
>>    // Set the mapping.
>> -  for (unsigned i = 0, e = GroupDiags.size(); i != e; ++i)
>> -    setSeverity(GroupDiags[i], Map, Loc);
>> +  for (diag::kind Diag : GroupDiags)
>> +    setSeverity(Diag, Map, Loc);
>>
>>    return false;
>>  }
>>
>>
>> _______________________________________________
>> cfe-commits mailing list
>> cfe-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
> _______________________________________________
> cfe-commits mailing list
> cfe-commits at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits