[clang-format] Break non-trailing comments, try 2

Summary:
This patch enables `BreakableToken` to manage the formatting of non-trailing
block comments. It is a refinement of https://reviews.llvm.org/D37007.
We discovered that the optimizer outsmarts us on cases where breaking the comment
costs considerably less than breaking after the comment. This patch addresses
this by ensuring that a newline is inserted between a block comment and the next
token.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D37695

llvm-svn: 315893

1 files changed, 14 insertions, 1 deletions

diff --git a/clang/lib/Format/ContinuationIndenter.cpp b/clang/lib/Format/ContinuationIndenter.cpp
index b438a3f64e7..b57b8de2e70 100644
--- a/clang/lib/Format/ContinuationIndenter.cpp
+++ b/clang/lib/Format/ContinuationIndenter.cpp
@@ -106,6 +106,7 @@ LineState ContinuationIndenter::getInitialState(unsigned FirstIndent,
                                    /*AvoidBinPacking=*/false,
                                    /*NoLineBreak=*/false));
   State.LineContainsContinuedForLoopSection = false;
+  State.NoContinuation = false;
   State.StartOfStringLiteral = 0;
   State.StartOfLineLevel = 0;
   State.LowestLevelOnLine = 0;
@@ -322,6 +323,12 @@ bool ContinuationIndenter::mustBreak(const LineState &State) {
                                      Previous.TokenText == "\'\\n\'"))))
     return true;
 
+  if (Previous.is(TT_BlockComment) && Previous.IsMultiline)
+    return true;
+
+  if (State.NoContinuation)
+    return true;
+
   return false;
 }
 
@@ -331,6 +338,8 @@ unsigned ContinuationIndenter::addTokenToState(LineState &State, bool Newline,
   const FormatToken &Current = *State.NextToken;
 
   assert(!State.Stack.empty());
+  State.NoContinuation = false;
+
   if ((Current.is(TT_ImplicitStringLiteral) &&
        (Current.Previous->Tok.getIdentifierInfo() == nullptr ||
         Current.Previous->Tok.getIdentifierInfo()->getPPKeywordID() ==
@@ -1286,7 +1295,7 @@ unsigned ContinuationIndenter::breakProtrudingToken(const FormatToken &Current,
       return 0;
     }
   } else if (Current.is(TT_BlockComment)) {
-    if (!Current.isTrailingComment() || !Style.ReflowComments ||
+    if (!Style.ReflowComments ||
         // If a comment token switches formatting, like
         // /* clang-format on */, we don't want to break it further,
         // but we may still want to adjust its indentation.
@@ -1332,6 +1341,7 @@ unsigned ContinuationIndenter::breakProtrudingToken(const FormatToken &Current,
     ReflowInProgress = SplitBefore.first != StringRef::npos;
     TailOffset =
         ReflowInProgress ? (SplitBefore.first + SplitBefore.second) : 0;
+    BreakInserted = BreakInserted || Token->introducesBreakBefore(LineIndex);
     if (!DryRun)
       Token->replaceWhitespaceBefore(LineIndex, RemainingTokenColumns,
                                      RemainingSpace, SplitBefore, Whitespaces);
@@ -1408,6 +1418,9 @@ unsigned ContinuationIndenter::breakProtrudingToken(const FormatToken &Current,
         State.Stack[i].BreakBeforeParameter = true;
     }
 
+    if (Current.is(TT_BlockComment))
+      State.NoContinuation = true;
+
     Penalty += Current.isStringLiteral() ? Style.PenaltyBreakString
                                          : Style.PenaltyBreakComment;