Revert unnecessary and incorrect change made to GraphWriter

[jamieschmeiser]

Summary

As pointed out in https://github.com/llvm/llvm-project/issues/52610, the changes to GraphWriter made
in https://reviews.llvm.org/D87202 introduced some bad code and the changes are actually unnecessary
for -print-changed=dot-cfg. The code in question is guarded by a call to
DefaultDOTGraphTraits::hasEdgeDestLabels() which is always false when the graph writer is called for
-print-changed=dot-cfg. Revert this section of the changes.

[aeubanks]

not familiar enough with html, I'll let somebody else review this

[jrtc27]

Thanks. It'd be nice if everything supported HTML output (and that were an option somewhere, not hard-coded), but given the rest of the code for this case needs updating to support HTML this seems fine as a fix for the regression.

[jamieschmeiser]

Yes, it would be nice. BTW, the choice is not hard coded but is specified with DefaultDOTGraphTraits::renderNodesUsingHTML() and stored in the ctor since it is unlikely that an HTML and non-HTML mix would be desirable.

[jrtc27]

That's what I mean by hard-coded; the code has non-overridable values baked in for specific classes as far as LLVM as a whole is concerned, even if it's not in GraphWriter.h. I'm talking from a command-line standpoint; it'd be nice to be able to say -mllvm -view-sched-dags-html or something and have the user be able to request a different format.

[jamieschmeiser]

I see. Yes, that would be a nice feature.

[xgupta]

A test case is missing, but I tested on local system, above reported issue is now fixed.

llvm/include/llvm/Support/GraphWriter.h

if (DTraits.hasEdgeDestLabels()) {
 
       unsigned i = 0, e = DTraits.numEdgeDestLabels(Node);
       for (; i != e && i != 64; ++i) {
         if (i) O << "|";
         O << "<d" << i << ">"
           << DOT::EscapeString(DTraits.getEdgeDestLabel(Node, i));
       }
 
-      if (RenderUsingHTML)
-        O << "<td colspan=\"1\">... truncated</td>";
-      else if (i != e)
-        O << "|<d64>truncated...}";
+      if (i != e)
+        O << "|<d64>truncated...";
+      O << "}";
     }
 
     if (RenderUsingHTML)
       O << "</tr></table>>";
     else
       O << "}\"";
     O << "];\n"; // Finish printing the "node" line