[llvm] r194496 - GraphViz CFGPrinter: wrap long lines.

[Sean Silva]

On Tue, Nov 12, 2013 at 10:09 PM, Andrew Trick <atrick at apple.com> wrote:

>
> On Nov 12, 2013, at 6:26 PM, Sean Silva <silvas at purdue.edu> wrote:
>
> Out of curiousity, what was the motivation for this? It seems to add a lot
> of (honestly pretty unmaintable) complexity, and isn't this output meant to
> be fed to another tool.
>
>
> We have about as different an idea of unmaintainable as I could imagine.
> This is a trivial bit of code completely confined to a single loop that
> hasn’t been touched since Chris wrote it in 2003.
>

I'm not claiming that the previous code was a model of perfection, but this
commit caused it to cross a mental "ad-hoc poorly specified
loop"-complexity threshold of mine.


>
> If you’ll notice the existing comment on the loop is “Process string
> output to make it nicer…”
>
> Very long lines make it impossible for GraphViz to layout the graph such
> the the CFG structure is evident.  That’s definitely not nice. I don’t like
> the DOT language or the tool, but I need to make it work for our purpose.
> I’d be happy with any alternate implementation that you provide.
>

Oh, I see now. This is modifying the content of string literals, not tokens
in the source language. Sorry. Yeah I can see that making sense now (I was
thinking that this was just wrapping the actual .dot file code).

-- Sean Silva


>
> -Andy
>
> On Tue, Nov 12, 2013 at 1:06 PM, Andrew Trick <atrick at apple.com> wrote:
>
>> Author: atrick
>> Date: Tue Nov 12 12:06:09 2013
>> New Revision: 194496
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=194496&view=rev
>> Log:
>> GraphViz CFGPrinter: wrap long lines.
>>
>> Modified:
>>     llvm/trunk/include/llvm/Analysis/CFGPrinter.h
>>
>> Modified: llvm/trunk/include/llvm/Analysis/CFGPrinter.h
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Analysis/CFGPrinter.h?rev=194496&r1=194495&r2=194496&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/include/llvm/Analysis/CFGPrinter.h (original)
>> +++ llvm/trunk/include/llvm/Analysis/CFGPrinter.h Tue Nov 12 12:06:09 2013
>> @@ -46,6 +46,7 @@ struct DOTGraphTraits<const Function*> :
>>
>>    static std::string getCompleteNodeLabel(const BasicBlock *Node,
>>                                            const Function *) {
>> +    enum { MaxColumns = 80 };
>>      std::string Str;
>>      raw_string_ostream OS(Str);
>>
>> @@ -59,16 +60,32 @@ struct DOTGraphTraits<const Function*> :
>>      if (OutStr[0] == '\n') OutStr.erase(OutStr.begin());
>>
>>      // Process string output to make it nicer...
>> -    for (unsigned i = 0; i != OutStr.length(); ++i)
>> +    unsigned ColNum = 0;
>> +    unsigned LastSpace = 0;
>> +    for (unsigned i = 0; i != OutStr.length(); ++i) {
>>        if (OutStr[i] == '\n') {                            // Left justify
>>          OutStr[i] = '\\';
>>          OutStr.insert(OutStr.begin()+i+1, 'l');
>> +        ColNum = 0;
>> +        LastSpace = 0;
>>        } else if (OutStr[i] == ';') {                      // Delete
>> comments!
>>          unsigned Idx = OutStr.find('\n', i+1);            // Find end of
>> line
>>          OutStr.erase(OutStr.begin()+i, OutStr.begin()+Idx);
>>          --i;
>> +      } else if (ColNum == MaxColumns) {                  // Wrap lines.
>> +        if (LastSpace) {
>> +          OutStr.insert(LastSpace, "\\l...");
>> +          ColNum = i - LastSpace;
>> +          LastSpace = 0;
>> +          i += 3; // The loop will advance 'i' again.
>> +        }
>> +        // Else keep trying to find a space.
>>        }
>> -
>> +      else
>> +        ++ColNum;
>> +      if (OutStr[i] == ' ')
>> +        LastSpace = i;
>> +    }
>>      return OutStr;
>>    }
>>
>>
>>
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>
>
>
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