[clang-format][PR45816] Add AlignConsecutiveBitFields

[JakeMerdichAMD]

Summary

The following revision follows D80115 since @MyDeveloperDay and I apparently both had the same idea at the same time, for https://bugs.llvm.org/show_bug.cgi?id=45816 and my efforts on tooling support for AMDVLK, respectively.

This option aligns adjacent bitfield separators across lines, in a manner similar to AlignConsecutiveAssignments and friends.

Example:

struct RawFloat {
  uint32_t sign : 1;
  uint32_t exponent : 8;
  uint32_t mantissa : 23;
};

would become

struct RawFloat {
  uint32_t sign     : 1;
  uint32_t exponent : 8;
  uint32_t mantissa : 23;
};

This also handles c++2a style bitfield-initializers with AlignConsecutiveAssignments.

struct RawFloat {
  uint32_t sign     : 1  = 0;
  uint32_t exponent : 8  = 127;
  uint32_t mantissa : 23 = 0;
}; // defaults to 1.0f

Things this change does not do:

• Align multiple comma-chained bitfield variables. None of the other AlignConsecutive* options seem to implement that either.
• Detect bitfields that have a width specified with something other than a numeric literal (ie, int a : SOME_MACRO;). That'd be fairly difficult to parse and is rare.

[MyDeveloperDay]

The LGTM (nit: clang-format)

[JakeMerdichAMD]

Reformat with a newer clang-format

[MyDeveloperDay]

LGTM

[JakeMerdichAMD]

Can I get your assistance committing this?

clang/docs/ClangFormatStyleOptions.rst

**AlignConsecutiveAssignments** (``bool``)
   will result in formattings like
 
   .. code-block:: c++
 
     int aaaa = 12;
     int b    = 23;
     int ccc  = 23;
 
+**AlignConsecutiveBitFields** (``bool``)
+  If ``true``, aligns consecutive bitfield members.
+
+  This will align the bitfield separator of consecutive lines. This
+  will result in formattings like
+
+  .. code-block:: c++
+
+    int aaaa : 1;
+    int b    : 12;
+    int ccc  : 8;
+
 **AlignConsecutiveDeclarations** (``bool``)
   If ``true``, aligns consecutive declarations.
 
   This will align the declaration names of consecutive lines. This
   will result in formattings like
 
   .. code-block:: c++
 

clang/docs/ReleaseNotes.rst

.. code-block:: c++
         });
 
       false:
       connect([]() {
           foo();
           bar();
         });
 
+- Option ``AlignConsecutiveBitFields`` has been added to align bit field
+  declarations across multiple adjacent lines
+
+  .. code-block:: c++
+
+      true:
+        bool aaa  : 1;
+        bool a    : 1;
+        bool bb   : 1;
+
+      false:
+        bool aaa : 1;
+        bool a : 1;
+        bool bb : 1;
+
 libclang
 --------
 
 - ...
 
 Static Analyzer
 ---------------
 

clang/include/clang/Format/Format.h

struct FormatStyle {
   /// will result in formattings like
   /// \code
   ///   int aaaa = 12;
   ///   int b    = 23;
   ///   int ccc  = 23;
   /// \endcode
   bool AlignConsecutiveAssignments;
 
+  /// If ``true``, aligns consecutive bitfield members.
+  ///
+  /// This will align the bitfield separators of consecutive lines. This
+  /// will result in formattings like
+  /// \code
+  ///   int aaaa : 1;
+  ///   int b    : 12;
+  ///   int ccc  : 8;
+  /// \endcode
+  bool AlignConsecutiveBitFields;
+
   /// If ``true``, aligns consecutive declarations.
   ///
   /// This will align the declaration names of consecutive lines. This
   /// will result in formattings like
   /// \code
   ///   int         aaaa = 12;
   ///   float       b = 23;
   ///   std::string ccc = 23;

 
   /// The way to use tab characters in the resulting file.
   UseTabStyle UseTab;
 
   bool operator==(const FormatStyle &R) const {
     return AccessModifierOffset == R.AccessModifierOffset &&
            AlignAfterOpenBracket == R.AlignAfterOpenBracket &&
            AlignConsecutiveAssignments == R.AlignConsecutiveAssignments &&
+           AlignConsecutiveBitFields == R.AlignConsecutiveBitFields &&
            AlignConsecutiveDeclarations == R.AlignConsecutiveDeclarations &&
            AlignEscapedNewlines == R.AlignEscapedNewlines &&
            AlignOperands == R.AlignOperands &&
            AlignTrailingComments == R.AlignTrailingComments &&
            AllowAllArgumentsOnNextLine == R.AllowAllArgumentsOnNextLine &&
            AllowAllConstructorInitializersOnNextLine ==
                R.AllowAllConstructorInitializersOnNextLine &&
            AllowAllParametersOfDeclarationOnNextLine ==

clang/lib/Format/Format.cpp

if (!IO.outputting()) {
                      Style.SpaceBeforeParens);
     }
 
     IO.mapOptional("AccessModifierOffset", Style.AccessModifierOffset);
     IO.mapOptional("AlignAfterOpenBracket", Style.AlignAfterOpenBracket);
     IO.mapOptional("AlignConsecutiveMacros", Style.AlignConsecutiveMacros);
     IO.mapOptional("AlignConsecutiveAssignments",
                    Style.AlignConsecutiveAssignments);
+    IO.mapOptional("AlignConsecutiveBitFields",
+                   Style.AlignConsecutiveBitFields);
     IO.mapOptional("AlignConsecutiveDeclarations",
                    Style.AlignConsecutiveDeclarations);
     IO.mapOptional("AlignEscapedNewlines", Style.AlignEscapedNewlines);
     IO.mapOptional("AlignOperands", Style.AlignOperands);
     IO.mapOptional("AlignTrailingComments", Style.AlignTrailingComments);
     IO.mapOptional("AllowAllArgumentsOnNextLine",
                    Style.AllowAllArgumentsOnNextLine);
     IO.mapOptional("AllowAllConstructorInitializersOnNextLine",
FormatStyle getLLVMStyle(FormatStyle::LanguageKind Language) {
   FormatStyle LLVMStyle;
   LLVMStyle.Language = Language;
   LLVMStyle.AccessModifierOffset = -2;
   LLVMStyle.AlignEscapedNewlines = FormatStyle::ENAS_Right;
   LLVMStyle.AlignAfterOpenBracket = FormatStyle::BAS_Align;
   LLVMStyle.AlignOperands = FormatStyle::OAS_Align;
   LLVMStyle.AlignTrailingComments = true;
   LLVMStyle.AlignConsecutiveAssignments = false;
+  LLVMStyle.AlignConsecutiveBitFields = false;
   LLVMStyle.AlignConsecutiveDeclarations = false;
   LLVMStyle.AlignConsecutiveMacros = false;
   LLVMStyle.AllowAllArgumentsOnNextLine = true;
   LLVMStyle.AllowAllConstructorInitializersOnNextLine = true;
   LLVMStyle.AllowAllParametersOfDeclarationOnNextLine = true;
   LLVMStyle.AllowShortEnumsOnASingleLine = true;
   LLVMStyle.AllowShortFunctionsOnASingleLine = FormatStyle::SFS_All;
   LLVMStyle.AllowShortBlocksOnASingleLine = FormatStyle::SBS_Never;

clang/lib/Format/WhitespaceManager.h

private:
   void calculateLineBreakInformation();
 
   /// \brief Align consecutive C/C++ preprocessor macros over all \c Changes.
   void alignConsecutiveMacros();
 
   /// Align consecutive assignments over all \c Changes.
   void alignConsecutiveAssignments();
 
+  /// Align consecutive bitfields over all \c Changes.
+  void alignConsecutiveBitFields();
+
   /// Align consecutive declarations over all \c Changes.
   void alignConsecutiveDeclarations();
 
   /// Align consecutive declarations over all \c Changes.
   void alignChainedConditionals();
 
   /// Align trailing comments over all \c Changes.
   void alignTrailingComments();

clang/lib/Format/WhitespaceManager.cpp

 const tooling::Replacements &WhitespaceManager::generateReplacements() {
   if (Changes.empty())
     return Replaces;
 
   llvm::sort(Changes, Change::IsBeforeInFile(SourceMgr));
   calculateLineBreakInformation();
   alignConsecutiveMacros();
   alignConsecutiveDeclarations();
+  alignConsecutiveBitFields();
   alignConsecutiveAssignments();
   alignChainedConditionals();
   alignTrailingComments();
   alignEscapedNewlines();
   generateChanges();
 
   return Replaces;
 }
AlignTokens(
         if (&C != &Changes.back() && (&C + 1)->NewlinesBefore > 0)
           return false;
 
         return C.Tok->is(tok::equal);
       },
       Changes, /*StartAt=*/0);
 }
 
+void WhitespaceManager::alignConsecutiveBitFields() {
+  if (!Style.AlignConsecutiveBitFields)
+    return;
+
+  AlignTokens(Style,
+              [&](Change const &C) {
+                // Do not align on ':' that is first on a line.
+                if (C.NewlinesBefore > 0)
+                  return false;
+
+                // Do not align on ':' that is last on a line.
+                if (&C != &Changes.back() && (&C + 1)->NewlinesBefore > 0)
+                  return false;
+
+                return C.Tok->is(TT_BitFieldColon);
+              },
+              Changes, /*StartAt=*/0);
+}
+
 void WhitespaceManager::alignConsecutiveDeclarations() {
   if (!Style.AlignConsecutiveDeclarations)
     return;
 
   // FIXME: Currently we don't handle properly the PointerAlignment: Right
   // The * and & are not aligned and are left dangling. Something has to be done
   // about it, but it raises the question of alignment of code like:
   //   const char* const* v1;

clang/unittests/Format/FormatTest.cpp

verifyFormat("for (int i = 0; i < 1; i++)\n"
                "  int x = 1;\n",
                Alignment);
   verifyFormat("for (i = 0; i < 1; i++)\n"
                "  x = 1;\n"
                "y = 1;\n",
                Alignment);
 }
 
+TEST_F(FormatTest, AlignConsecutiveBitFields) {
+  FormatStyle Alignment = getLLVMStyle();
+  Alignment.AlignConsecutiveBitFields = true;
+  verifyFormat("int const a     : 5;\n"
+               "int oneTwoThree : 23;",
+               Alignment);
+
+  // Initializers are allowed starting with c++2a
+  verifyFormat("int const a     : 5 = 1;\n"
+               "int oneTwoThree : 23 = 0;",
+               Alignment);
+
+  Alignment.AlignConsecutiveDeclarations = true;
+  verifyFormat("int const a           : 5;\n"
+               "int       oneTwoThree : 23;",
+               Alignment);
+
+  verifyFormat("int const a           : 5;  // comment\n"
+               "int       oneTwoThree : 23; // comment",
+               Alignment);
+
+  verifyFormat("int const a           : 5 = 1;\n"
+               "int       oneTwoThree : 23 = 0;",
+               Alignment);
+
+  Alignment.AlignConsecutiveAssignments = true;
+  verifyFormat("int const a           : 5  = 1;\n"
+               "int       oneTwoThree : 23 = 0;",
+               Alignment);
+  verifyFormat("int const a           : 5  = {1};\n"
+               "int       oneTwoThree : 23 = 0;",
+               Alignment);
+
+  // Known limitations: ':' is only recognized as a bitfield colon when
+  // followed by a number.
+  /*
+  verifyFormat("int oneTwoThree : SOME_CONSTANT;\n"
+               "int a           : 5;",
+               Alignment);
+  */
+}
+
 TEST_F(FormatTest, AlignConsecutiveDeclarations) {
   FormatStyle Alignment = getLLVMStyle();
   Alignment.AlignConsecutiveMacros = true;
   Alignment.AlignConsecutiveDeclarations = false;
   verifyFormat("float const a = 5;\n"
                "int oneTwoThree = 123;",
                Alignment);
   verifyFormat("int a = 5;\n"
#define CHECK_PARSE(TEXT, FIELD, VALUE)                                        \
   EXPECT_EQ(0, parseConfiguration(TEXT, &Style).value());                      \
   EXPECT_EQ(VALUE, Style.FIELD)
 
 TEST_F(FormatTest, ParsesConfigurationBools) {
   FormatStyle Style = {};
   Style.Language = FormatStyle::LK_Cpp;
   CHECK_PARSE_BOOL(AlignTrailingComments);
   CHECK_PARSE_BOOL(AlignConsecutiveAssignments);
+  CHECK_PARSE_BOOL(AlignConsecutiveBitFields);
   CHECK_PARSE_BOOL(AlignConsecutiveDeclarations);
   CHECK_PARSE_BOOL(AlignConsecutiveMacros);
   CHECK_PARSE_BOOL(AllowAllArgumentsOnNextLine);
   CHECK_PARSE_BOOL(AllowAllConstructorInitializersOnNextLine);
   CHECK_PARSE_BOOL(AllowAllParametersOfDeclarationOnNextLine);
   CHECK_PARSE_BOOL(AllowShortCaseLabelsOnASingleLine);
   CHECK_PARSE_BOOL(AllowShortEnumsOnASingleLine);
   CHECK_PARSE_BOOL(AllowShortLoopsOnASingleLine);