[clang][NFC] Refactor enums that hold size of Type and DeclContext bit-fields

[Endilll]

This patch refactor said enums to hold total size of a bit-field, and not just non-inherited bits. This brings Type and DeclContext in line with Comment and Stmt. It also makes it unnecessary to list all transitive bases of a bit-field as unnamed bit-fields, which makes it more friendly towards debuggers.

[llvmbot]

@llvm/pr-subscribers-clang

@llvm/pr-subscribers-clang-modules

Author: Vlad Serebrennikov (Endilll)

Changes

This patch refactor said enums to hold total size of a bit-field, and not just non-inherited bits. This brings Type and DeclContext in line with Comment and Stmt. It also makes it unnecessary to list all transitive bases of a bit-field as unnamed bit-fields, which makes it more friendly towards debuggers.

---

Full diff: https://github.com/llvm/llvm-project/pull/70296.diff

3 Files Affected:

• (modified) clang/include/clang/AST/DeclBase.h (+21-28)
• (modified) clang/include/clang/AST/Type.h (+3-3)
• (modified) clang/lib/Serialization/ASTWriterDecl.cpp (+9-9)

diff --git a/clang/include/clang/AST/DeclBase.h b/clang/include/clang/AST/DeclBase.h
index d383e46e22e16f4..e9eb43900cf5371 100644
--- a/clang/include/clang/AST/DeclBase.h
+++ b/clang/include/clang/AST/DeclBase.h
@@ -1515,16 +1515,14 @@ class DeclContext {
     uint64_t IsThisDeclarationADemotedDefinition : 1;
   };
 
-  /// Number of non-inherited bits in TagDeclBitfields.
-  enum { NumTagDeclBits = 10 };
+  /// Number of inherited and non-inherited bits in TagDeclBitfields.
+  enum { NumTagDeclBits = NumDeclContextBits + 10 };
 
   /// Stores the bits used by EnumDecl.
   /// If modified NumEnumDeclBit and the accessor
   /// methods in EnumDecl should be updated appropriately.
   class EnumDeclBitfields {
     friend class EnumDecl;
-    /// For the bits in DeclContextBitfields.
-    uint64_t : NumDeclContextBits;
     /// For the bits in TagDeclBitfields.
     uint64_t : NumTagDeclBits;
 
@@ -1554,16 +1552,14 @@ class DeclContext {
     uint64_t HasODRHash : 1;
   };
 
-  /// Number of non-inherited bits in EnumDeclBitfields.
-  enum { NumEnumDeclBits = 20 };
+  /// Number of inherited and non-inherited bits in EnumDeclBitfields.
+  enum { NumEnumDeclBits = NumTagDeclBits + 20 };
 
   /// Stores the bits used by RecordDecl.
   /// If modified NumRecordDeclBits and the accessor
   /// methods in RecordDecl should be updated appropriately.
   class RecordDeclBitfields {
     friend class RecordDecl;
-    /// For the bits in DeclContextBitfields.
-    uint64_t : NumDeclContextBits;
     /// For the bits in TagDeclBitfields.
     uint64_t : NumTagDeclBits;
 
@@ -1615,8 +1611,8 @@ class DeclContext {
     uint64_t ODRHash : 26;
   };
 
-  /// Number of non-inherited bits in RecordDeclBitfields.
-  enum { NumRecordDeclBits = 41 };
+  /// Number of inherited and non-inherited bits in RecordDeclBitfields.
+  enum { NumRecordDeclBits = NumTagDeclBits + 41 };
 
   /// Stores the bits used by OMPDeclareReductionDecl.
   /// If modified NumOMPDeclareReductionDeclBits and the accessor
@@ -1631,8 +1627,9 @@ class DeclContext {
     uint64_t InitializerKind : 2;
   };
 
-  /// Number of non-inherited bits in OMPDeclareReductionDeclBitfields.
-  enum { NumOMPDeclareReductionDeclBits = 2 };
+  /// Number of inherited and non-inherited bits in
+  /// OMPDeclareReductionDeclBitfields.
+  enum { NumOMPDeclareReductionDeclBits = NumDeclContextBits + 2 };
 
   /// Stores the bits used by FunctionDecl.
   /// If modified NumFunctionDeclBits and the accessor
@@ -1711,16 +1708,14 @@ class DeclContext {
     uint64_t FriendConstraintRefersToEnclosingTemplate : 1;
   };
 
-  /// Number of non-inherited bits in FunctionDeclBitfields.
-  enum { NumFunctionDeclBits = 31 };
+  /// Number of inherited and non-inherited bits in FunctionDeclBitfields.
+  enum { NumFunctionDeclBits = NumDeclContextBits + 31 };
 
   /// Stores the bits used by CXXConstructorDecl. If modified
   /// NumCXXConstructorDeclBits and the accessor
   /// methods in CXXConstructorDecl should be updated appropriately.
   class CXXConstructorDeclBitfields {
     friend class CXXConstructorDecl;
-    /// For the bits in DeclContextBitfields.
-    uint64_t : NumDeclContextBits;
     /// For the bits in FunctionDeclBitfields.
     uint64_t : NumFunctionDeclBits;
 
@@ -1739,10 +1734,8 @@ class DeclContext {
     uint64_t IsSimpleExplicit : 1;
   };
 
-  /// Number of non-inherited bits in CXXConstructorDeclBitfields.
-  enum {
-    NumCXXConstructorDeclBits = 64 - NumDeclContextBits - NumFunctionDeclBits
-  };
+  /// Number of inherited and non-inherited bits in CXXConstructorDeclBitfields.
+  enum { NumCXXConstructorDeclBits = 64 };
 
   /// Stores the bits used by ObjCMethodDecl.
   /// If modified NumObjCMethodDeclBits and the accessor
@@ -1803,8 +1796,8 @@ class DeclContext {
     uint64_t HasSkippedBody : 1;
   };
 
-  /// Number of non-inherited bits in ObjCMethodDeclBitfields.
-  enum { NumObjCMethodDeclBits = 24 };
+  /// Number of inherited and non-inherited bits in ObjCMethodDeclBitfields.
+  enum { NumObjCMethodDeclBits = NumDeclContextBits + 24 };
 
   /// Stores the bits used by ObjCContainerDecl.
   /// If modified NumObjCContainerDeclBits and the accessor
@@ -1819,10 +1812,10 @@ class DeclContext {
     SourceLocation AtStart;
   };
 
-  /// Number of non-inherited bits in ObjCContainerDeclBitfields.
+  /// Number of inherited and non-inherited bits in ObjCContainerDeclBitfields.
   /// Note that here we rely on the fact that SourceLocation is 32 bits
   /// wide. We check this with the static_assert in the ctor of DeclContext.
-  enum { NumObjCContainerDeclBits = 64 - NumDeclContextBits };
+  enum { NumObjCContainerDeclBits = 64 };
 
   /// Stores the bits used by LinkageSpecDecl.
   /// If modified NumLinkageSpecDeclBits and the accessor
@@ -1843,8 +1836,8 @@ class DeclContext {
     uint64_t HasBraces : 1;
   };
 
-  /// Number of non-inherited bits in LinkageSpecDeclBitfields.
-  enum { NumLinkageSpecDeclBits = 4 };
+  /// Number of inherited and non-inherited bits in LinkageSpecDeclBitfields.
+  enum { NumLinkageSpecDeclBits = NumDeclContextBits + 4 };
 
   /// Stores the bits used by BlockDecl.
   /// If modified NumBlockDeclBits and the accessor
@@ -1869,8 +1862,8 @@ class DeclContext {
     uint64_t CanAvoidCopyToHeap : 1;
   };
 
-  /// Number of non-inherited bits in BlockDeclBitfields.
-  enum { NumBlockDeclBits = 5 };
+  /// Number of inherited and non-inherited bits in BlockDeclBitfields.
+  enum { NumBlockDeclBits = NumDeclContextBits + 5 };
 
   /// Pointer to the data structure used to lookup declarations
   /// within this context (or a DependentStoredDeclsMap if this is a
diff --git a/clang/include/clang/AST/Type.h b/clang/include/clang/AST/Type.h
index e3dbe3b8a45cc3e..f52d72bdb2d4155 100644
--- a/clang/include/clang/AST/Type.h
+++ b/clang/include/clang/AST/Type.h
@@ -1663,11 +1663,12 @@ class alignas(TypeAlignment) Type : public ExtQualsTypeCommonBase {
     /// Actually an ArrayType::ArraySizeModifier.
     unsigned SizeModifier : 3;
   };
+  enum { NumArrayTypeBits = NumTypeBits + 3 + 3 };
 
   class ConstantArrayTypeBitfields {
     friend class ConstantArrayType;
 
-    unsigned : NumTypeBits + 3 + 3;
+    unsigned : NumArrayTypeBits;
 
     /// Whether we have a stored size expression.
     unsigned HasStoredSizeExpr : 1;
@@ -1780,7 +1781,7 @@ class alignas(TypeAlignment) Type : public ExtQualsTypeCommonBase {
     unsigned Keyword : 8;
   };
 
-  enum { NumTypeWithKeywordBits = 8 };
+  enum { NumTypeWithKeywordBits = NumTypeBits + 8 };
 
   class ElaboratedTypeBitfields {
     friend class ElaboratedType;
@@ -1913,7 +1914,6 @@ class alignas(TypeAlignment) Type : public ExtQualsTypeCommonBase {
   class DependentTemplateSpecializationTypeBitfields {
     friend class DependentTemplateSpecializationType;
 
-    unsigned : NumTypeBits;
     unsigned : NumTypeWithKeywordBits;
 
     /// The number of template arguments named in this class template
diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 8a2ea7c7624ceb8..b3364113abf15ba 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -431,7 +431,7 @@ void ASTDeclWriter::VisitTypeAliasDecl(TypeAliasDecl *D) {
 }
 
 void ASTDeclWriter::VisitTagDecl(TagDecl *D) {
-  static_assert(DeclContext::NumTagDeclBits == 10,
+  static_assert(DeclContext::NumTagDeclBits == 23,
                 "You need to update the serializer after you change the "
                 "TagDeclBits");
 
@@ -459,7 +459,7 @@ void ASTDeclWriter::VisitTagDecl(TagDecl *D) {
 }
 
 void ASTDeclWriter::VisitEnumDecl(EnumDecl *D) {
-  static_assert(DeclContext::NumEnumDeclBits == 20,
+  static_assert(DeclContext::NumEnumDeclBits == 43,
                 "You need to update the serializer after you change the "
                 "EnumDeclBits");
 
@@ -506,7 +506,7 @@ void ASTDeclWriter::VisitEnumDecl(EnumDecl *D) {
 }
 
 void ASTDeclWriter::VisitRecordDecl(RecordDecl *D) {
-  static_assert(DeclContext::NumRecordDeclBits == 41,
+  static_assert(DeclContext::NumRecordDeclBits == 64,
                 "You need to update the serializer after you change the "
                 "RecordDeclBits");
 
@@ -578,7 +578,7 @@ void ASTDeclWriter::VisitDeclaratorDecl(DeclaratorDecl *D) {
 }
 
 void ASTDeclWriter::VisitFunctionDecl(FunctionDecl *D) {
-  static_assert(DeclContext::NumFunctionDeclBits == 31,
+  static_assert(DeclContext::NumFunctionDeclBits == 44,
                 "You need to update the serializer after you change the "
                 "FunctionDeclBits");
 
@@ -726,7 +726,7 @@ void ASTDeclWriter::VisitCXXDeductionGuideDecl(CXXDeductionGuideDecl *D) {
 }
 
 void ASTDeclWriter::VisitObjCMethodDecl(ObjCMethodDecl *D) {
-  static_assert(DeclContext::NumObjCMethodDeclBits == 24,
+  static_assert(DeclContext::NumObjCMethodDeclBits == 37,
                 "You need to update the serializer after you change the "
                 "ObjCMethodDeclBits");
 
@@ -788,7 +788,7 @@ void ASTDeclWriter::VisitObjCTypeParamDecl(ObjCTypeParamDecl *D) {
 }
 
 void ASTDeclWriter::VisitObjCContainerDecl(ObjCContainerDecl *D) {
-  static_assert(DeclContext::NumObjCContainerDeclBits == 51,
+  static_assert(DeclContext::NumObjCContainerDeclBits == 64,
                 "You need to update the serializer after you change the "
                 "ObjCContainerDeclBits");
 
@@ -1268,7 +1268,7 @@ void ASTDeclWriter::VisitCapturedDecl(CapturedDecl *CD) {
 }
 
 void ASTDeclWriter::VisitLinkageSpecDecl(LinkageSpecDecl *D) {
-  static_assert(DeclContext::NumLinkageSpecDeclBits == 4,
+  static_assert(DeclContext::NumLinkageSpecDeclBits == 17,
                 "You need to update the serializer after you change the"
                 "LinkageSpecDeclBits");
 
@@ -1479,7 +1479,7 @@ void ASTDeclWriter::VisitCXXMethodDecl(CXXMethodDecl *D) {
 }
 
 void ASTDeclWriter::VisitCXXConstructorDecl(CXXConstructorDecl *D) {
-  static_assert(DeclContext::NumCXXConstructorDeclBits == 20,
+  static_assert(DeclContext::NumCXXConstructorDeclBits == 64,
                 "You need to update the serializer after you change the "
                 "CXXConstructorDeclBits");
 
@@ -1960,7 +1960,7 @@ void ASTDeclWriter::VisitOMPRequiresDecl(OMPRequiresDecl *D) {
 }
 
 void ASTDeclWriter::VisitOMPDeclareReductionDecl(OMPDeclareReductionDecl *D) {
-  static_assert(DeclContext::NumOMPDeclareReductionDeclBits == 2,
+  static_assert(DeclContext::NumOMPDeclareReductionDeclBits == 15,
                 "You need to update the serializer after you change the "
                 "NumOMPDeclareReductionDeclBits");
 

[ChuanqiXu9]

LGTM. Consistency is good.

[AaronBallman]

LGTM though I have some NFC suggestions you can take or leave.

[AaronBallman]

LGTM!