[AST] Move back BasePathSize to the bit-fields of CastExpr

The number of trailing CXXBaseSpecifiers in CastExpr was moved from
CastExprBitfields to a trailing object in r338489 (D50050). At this time these
bit-fields classes were only 32 bits wide. However later r345459 widened these
bit-field classes to 64 bits.

The reason for this change was that on 64 bit archs alignment requirements
caused 4 bytes of padding after the Stmt sub-object in nearly all expression
classes. Reusing this padding yielded an >10% reduction in the size used by all
statement/expressions when parsing all of Boost (on a 64 bit arch). This
increased the size of statement/expressions for 32 bits archs, but this can be
mitigated by moving more data to the bit-fields of Stmt (and moreover most
people now care about 64 bits archs as a host).

Therefore move back the number of CXXBaseSpecifiers in CastExpr to the
bit-fields of Stmt. This in effect mostly revert r338489 while keeping the
added test.

Differential Revision: https://reviews.llvm.org/D56358

Reviewed By: lebedev.ri

Reviewers: lebedev.ri, rjmccall
llvm-svn: 350741

6 files changed, 32 insertions, 125 deletions

diff --git a/clang/include/clang/AST/Expr.h b/clang/include/clang/AST/Expr.h
index 1c757b53308..3de73428829 100644
--- a/clang/include/clang/AST/Expr.h
+++ b/clang/include/clang/AST/Expr.h
@@ -2996,28 +2996,15 @@ public:
 /// representation in the source code (ExplicitCastExpr's derived
 /// classes).
 class CastExpr : public Expr {
-public:
-  using BasePathSizeTy = unsigned int;
-  static_assert(std::numeric_limits<BasePathSizeTy>::max() >= 16384,
-                "[implimits] Direct and indirect base classes [16384].");
-
-private:
   Stmt *Op;
 
   bool CastConsistency() const;
 
-  BasePathSizeTy *BasePathSize();
-
   const CXXBaseSpecifier * const *path_buffer() const {
     return const_cast<CastExpr*>(this)->path_buffer();
   }
   CXXBaseSpecifier **path_buffer();
 
-  void setBasePathSize(BasePathSizeTy basePathSize) {
-    assert(!path_empty() && basePathSize != 0);
-    *(BasePathSize()) = basePathSize;
-  }
-
 protected:
   CastExpr(StmtClass SC, QualType ty, ExprValueKind VK, const CastKind kind,
            Expr *op, unsigned BasePathSize)
@@ -3038,9 +3025,9 @@ protected:
         Op(op) {
     CastExprBits.Kind = kind;
     CastExprBits.PartOfExplicitCast = false;
-    CastExprBits.BasePathIsEmpty = BasePathSize == 0;
-    if (!path_empty())
-      setBasePathSize(BasePathSize);
+    CastExprBits.BasePathSize = BasePathSize;
+    assert((CastExprBits.BasePathSize == BasePathSize) &&
+           "BasePathSize overflow!");
     assert(CastConsistency());
   }
 
@@ -3048,9 +3035,9 @@ protected:
   CastExpr(StmtClass SC, EmptyShell Empty, unsigned BasePathSize)
     : Expr(SC, Empty) {
     CastExprBits.PartOfExplicitCast = false;
-    CastExprBits.BasePathIsEmpty = BasePathSize == 0;
-    if (!path_empty())
-      setBasePathSize(BasePathSize);
+    CastExprBits.BasePathSize = BasePathSize;
+    assert((CastExprBits.BasePathSize == BasePathSize) &&
+           "BasePathSize overflow!");
   }
 
 public:
@@ -3077,13 +3064,9 @@ public:
   NamedDecl *getConversionFunction() const;
 
   typedef CXXBaseSpecifier **path_iterator;
-  typedef const CXXBaseSpecifier * const *path_const_iterator;
-  bool path_empty() const { return CastExprBits.BasePathIsEmpty; }
-  unsigned path_size() const {
-    if (path_empty())
-      return 0U;
-    return *(const_cast<CastExpr *>(this)->BasePathSize());
-  }
+  typedef const CXXBaseSpecifier *const *path_const_iterator;
+  bool path_empty() const { return path_size() == 0; }
+  unsigned path_size() const { return CastExprBits.BasePathSize; }
   path_iterator path_begin() { return path_buffer(); }
   path_iterator path_end() { return path_buffer() + path_size(); }
   path_const_iterator path_begin() const { return path_buffer(); }
@@ -3131,13 +3114,8 @@ public:
 /// @endcode
 class ImplicitCastExpr final
     : public CastExpr,
-      private llvm::TrailingObjects<ImplicitCastExpr, CastExpr::BasePathSizeTy,
-                                    CXXBaseSpecifier *> {
-  size_t numTrailingObjects(OverloadToken<CastExpr::BasePathSizeTy>) const {
-    return path_empty() ? 0 : 1;
-  }
+      private llvm::TrailingObjects<ImplicitCastExpr, CXXBaseSpecifier *> {
 
-private:
   ImplicitCastExpr(QualType ty, CastKind kind, Expr *op,
                    unsigned BasePathLength, ExprValueKind VK)
     : CastExpr(ImplicitCastExprClass, ty, VK, kind, op, BasePathLength) { }
@@ -3245,8 +3223,7 @@ public:
 /// (Type)expr. For example: @c (int)f.
 class CStyleCastExpr final
     : public ExplicitCastExpr,
-      private llvm::TrailingObjects<CStyleCastExpr, CastExpr::BasePathSizeTy,
-                                    CXXBaseSpecifier *> {
+      private llvm::TrailingObjects<CStyleCastExpr, CXXBaseSpecifier *> {
   SourceLocation LPLoc; // the location of the left paren
   SourceLocation RPLoc; // the location of the right paren
 
@@ -3260,10 +3237,6 @@ class CStyleCastExpr final
   explicit CStyleCastExpr(EmptyShell Shell, unsigned PathSize)
     : ExplicitCastExpr(CStyleCastExprClass, Shell, PathSize) { }
 
-  size_t numTrailingObjects(OverloadToken<CastExpr::BasePathSizeTy>) const {
-    return path_empty() ? 0 : 1;
-  }
-
 public:
   static CStyleCastExpr *Create(const ASTContext &Context, QualType T,
                                 ExprValueKind VK, CastKind K,
diff --git a/clang/include/clang/AST/ExprCXX.h b/clang/include/clang/AST/ExprCXX.h
index 2b75b68f11c..6ef837a2fc4 100644
--- a/clang/include/clang/AST/ExprCXX.h
+++ b/clang/include/clang/AST/ExprCXX.h
@@ -325,8 +325,7 @@ public:
 /// \c static_cast<int>(1.0).
 class CXXStaticCastExpr final
     : public CXXNamedCastExpr,
-      private llvm::TrailingObjects<CXXStaticCastExpr, CastExpr::BasePathSizeTy,
-                                    CXXBaseSpecifier *> {
+      private llvm::TrailingObjects<CXXStaticCastExpr, CXXBaseSpecifier *> {
   CXXStaticCastExpr(QualType ty, ExprValueKind vk, CastKind kind, Expr *op,
                     unsigned pathSize, TypeSourceInfo *writtenTy,
                     SourceLocation l, SourceLocation RParenLoc,
@@ -337,10 +336,6 @@ class CXXStaticCastExpr final
   explicit CXXStaticCastExpr(EmptyShell Empty, unsigned PathSize)
       : CXXNamedCastExpr(CXXStaticCastExprClass, Empty, PathSize) {}
 
-  size_t numTrailingObjects(OverloadToken<CastExpr::BasePathSizeTy>) const {
-    return path_empty() ? 0 : 1;
-  }
-
 public:
   friend class CastExpr;
   friend TrailingObjects;
@@ -366,8 +361,7 @@ public:
 /// check to determine how to perform the type conversion.
 class CXXDynamicCastExpr final
     : public CXXNamedCastExpr,
-      private llvm::TrailingObjects<
-          CXXDynamicCastExpr, CastExpr::BasePathSizeTy, CXXBaseSpecifier *> {
+      private llvm::TrailingObjects<CXXDynamicCastExpr, CXXBaseSpecifier *> {
   CXXDynamicCastExpr(QualType ty, ExprValueKind VK, CastKind kind,
                      Expr *op, unsigned pathSize, TypeSourceInfo *writtenTy,
                      SourceLocation l, SourceLocation RParenLoc,
@@ -378,10 +372,6 @@ class CXXDynamicCastExpr final
   explicit CXXDynamicCastExpr(EmptyShell Empty, unsigned pathSize)
       : CXXNamedCastExpr(CXXDynamicCastExprClass, Empty, pathSize) {}
 
-  size_t numTrailingObjects(OverloadToken<CastExpr::BasePathSizeTy>) const {
-    return path_empty() ? 0 : 1;
-  }
-
 public:
   friend class CastExpr;
   friend TrailingObjects;
@@ -414,7 +404,6 @@ public:
 class CXXReinterpretCastExpr final
     : public CXXNamedCastExpr,
       private llvm::TrailingObjects<CXXReinterpretCastExpr,
-                                    CastExpr::BasePathSizeTy,
                                     CXXBaseSpecifier *> {
   CXXReinterpretCastExpr(QualType ty, ExprValueKind vk, CastKind kind,
                          Expr *op, unsigned pathSize,
@@ -427,10 +416,6 @@ class CXXReinterpretCastExpr final
   CXXReinterpretCastExpr(EmptyShell Empty, unsigned pathSize)
       : CXXNamedCastExpr(CXXReinterpretCastExprClass, Empty, pathSize) {}
 
-  size_t numTrailingObjects(OverloadToken<CastExpr::BasePathSizeTy>) const {
-    return path_empty() ? 0 : 1;
-  }
-
 public:
   friend class CastExpr;
   friend TrailingObjects;
@@ -458,8 +443,7 @@ public:
 /// value.
 class CXXConstCastExpr final
     : public CXXNamedCastExpr,
-      private llvm::TrailingObjects<CXXConstCastExpr, CastExpr::BasePathSizeTy,
-                                    CXXBaseSpecifier *> {
+      private llvm::TrailingObjects<CXXConstCastExpr, CXXBaseSpecifier *> {
   CXXConstCastExpr(QualType ty, ExprValueKind VK, Expr *op,
                    TypeSourceInfo *writtenTy, SourceLocation l,
                    SourceLocation RParenLoc, SourceRange AngleBrackets)
@@ -469,10 +453,6 @@ class CXXConstCastExpr final
   explicit CXXConstCastExpr(EmptyShell Empty)
       : CXXNamedCastExpr(CXXConstCastExprClass, Empty, 0) {}
 
-  size_t numTrailingObjects(OverloadToken<CastExpr::BasePathSizeTy>) const {
-    return path_empty() ? 0 : 1;
-  }
-
 public:
   friend class CastExpr;
   friend TrailingObjects;
@@ -1538,8 +1518,7 @@ public:
 /// \endcode
 class CXXFunctionalCastExpr final
     : public ExplicitCastExpr,
-      private llvm::TrailingObjects<
-          CXXFunctionalCastExpr, CastExpr::BasePathSizeTy, CXXBaseSpecifier *> {
+      private llvm::TrailingObjects<CXXFunctionalCastExpr, CXXBaseSpecifier *> {
   SourceLocation LParenLoc;
   SourceLocation RParenLoc;
 
@@ -1554,10 +1533,6 @@ class CXXFunctionalCastExpr final
   explicit CXXFunctionalCastExpr(EmptyShell Shell, unsigned PathSize)
       : ExplicitCastExpr(CXXFunctionalCastExprClass, Shell, PathSize) {}
 
-  size_t numTrailingObjects(OverloadToken<CastExpr::BasePathSizeTy>) const {
-    return path_empty() ? 0 : 1;
-  }
-
 public:
   friend class CastExpr;
   friend TrailingObjects;
diff --git a/clang/include/clang/AST/ExprObjC.h b/clang/include/clang/AST/ExprObjC.h
index ed3d3840b32..c7b305f3304 100644
--- a/clang/include/clang/AST/ExprObjC.h
+++ b/clang/include/clang/AST/ExprObjC.h
@@ -1574,8 +1574,7 @@ public:
 /// \endcode
 class ObjCBridgedCastExpr final
     : public ExplicitCastExpr,
-      private llvm::TrailingObjects<
-          ObjCBridgedCastExpr, CastExpr::BasePathSizeTy, CXXBaseSpecifier *> {
+      private llvm::TrailingObjects<ObjCBridgedCastExpr, CXXBaseSpecifier *> {
   friend class ASTStmtReader;
   friend class ASTStmtWriter;
   friend class CastExpr;
@@ -1585,10 +1584,6 @@ class ObjCBridgedCastExpr final
   SourceLocation BridgeKeywordLoc;
   unsigned Kind : 2;
 
-  size_t numTrailingObjects(OverloadToken<CastExpr::BasePathSizeTy>) const {
-    return path_empty() ? 0 : 1;
-  }
-
 public:
   ObjCBridgedCastExpr(SourceLocation LParenLoc, ObjCBridgeCastKind Kind,
                       CastKind CK, SourceLocation BridgeKeywordLoc,
diff --git a/clang/include/clang/AST/Stmt.h b/clang/include/clang/AST/Stmt.h
index 2f33fec71be..ff5baa21adf 100644
--- a/clang/include/clang/AST/Stmt.h
+++ b/clang/include/clang/AST/Stmt.h
@@ -481,7 +481,10 @@ protected:
 
     unsigned Kind : 6;
     unsigned PartOfExplicitCast : 1; // Only set for ImplicitCastExpr.
-    unsigned BasePathIsEmpty : 1;
+
+    /// The number of CXXBaseSpecifiers in the cast. 14 bits would be enough
+    /// here. ([implimits] Direct and indirect base classes [16384]).
+    unsigned BasePathSize;
   };
 
   class BinaryOperatorBitfields {
diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index 0775ff57737..7f6df179d43 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -1808,21 +1808,6 @@ NamedDecl *CastExpr::getConversionFunction() const {
   return nullptr;
 }
 
-CastExpr::BasePathSizeTy *CastExpr::BasePathSize() {
-  assert(!path_empty());
-  switch (getStmtClass()) {
-#define ABSTRACT_STMT(x)
-#define CASTEXPR(Type, Base)                                                   \
-  case Stmt::Type##Class:                                                      \
-    return static_cast<Type *>(this)                                           \
-        ->getTrailingObjects<CastExpr::BasePathSizeTy>();
-#define STMT(Type, Base)
-#include "clang/AST/StmtNodes.inc"
-  default:
-    llvm_unreachable("non-cast expressions not possible here");
-  }
-}
-
 CXXBaseSpecifier **CastExpr::path_buffer() {
   switch (getStmtClass()) {
 #define ABSTRACT_STMT(x)
@@ -1861,9 +1846,7 @@ ImplicitCastExpr *ImplicitCastExpr::Create(const ASTContext &C, QualType T,
                                            const CXXCastPath *BasePath,
                                            ExprValueKind VK) {
   unsigned PathSize = (BasePath ? BasePath->size() : 0);
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   ImplicitCastExpr *E =
     new (Buffer) ImplicitCastExpr(T, Kind, Operand, PathSize, VK);
   if (PathSize)
@@ -1874,9 +1857,7 @@ ImplicitCastExpr *ImplicitCastExpr::Create(const ASTContext &C, QualType T,
 
 ImplicitCastExpr *ImplicitCastExpr::CreateEmpty(const ASTContext &C,
                                                 unsigned PathSize) {
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   return new (Buffer) ImplicitCastExpr(EmptyShell(), PathSize);
 }
 
@@ -1887,9 +1868,7 @@ CStyleCastExpr *CStyleCastExpr::Create(const ASTContext &C, QualType T,
                                        TypeSourceInfo *WrittenTy,
                                        SourceLocation L, SourceLocation R) {
   unsigned PathSize = (BasePath ? BasePath->size() : 0);
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   CStyleCastExpr *E =
     new (Buffer) CStyleCastExpr(T, VK, K, Op, PathSize, WrittenTy, L, R);
   if (PathSize)
@@ -1900,9 +1879,7 @@ CStyleCastExpr *CStyleCastExpr::Create(const ASTContext &C, QualType T,
 
 CStyleCastExpr *CStyleCastExpr::CreateEmpty(const ASTContext &C,
                                             unsigned PathSize) {
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   return new (Buffer) CStyleCastExpr(EmptyShell(), PathSize);
 }
 
diff --git a/clang/lib/AST/ExprCXX.cpp b/clang/lib/AST/ExprCXX.cpp
index 699baa71f3e..3891f45c7fc 100644
--- a/clang/lib/AST/ExprCXX.cpp
+++ b/clang/lib/AST/ExprCXX.cpp
@@ -694,9 +694,7 @@ CXXStaticCastExpr *CXXStaticCastExpr::Create(const ASTContext &C, QualType T,
                                              SourceLocation RParenLoc,
                                              SourceRange AngleBrackets) {
   unsigned PathSize = (BasePath ? BasePath->size() : 0);
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   auto *E =
       new (Buffer) CXXStaticCastExpr(T, VK, K, Op, PathSize, WrittenTy, L,
                                      RParenLoc, AngleBrackets);
@@ -708,9 +706,7 @@ CXXStaticCastExpr *CXXStaticCastExpr::Create(const ASTContext &C, QualType T,
 
 CXXStaticCastExpr *CXXStaticCastExpr::CreateEmpty(const ASTContext &C,
                                                   unsigned PathSize) {
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   return new (Buffer) CXXStaticCastExpr(EmptyShell(), PathSize);
 }
 
@@ -723,9 +719,7 @@ CXXDynamicCastExpr *CXXDynamicCastExpr::Create(const ASTContext &C, QualType T,
                                                SourceLocation RParenLoc,
                                                SourceRange AngleBrackets) {
   unsigned PathSize = (BasePath ? BasePath->size() : 0);
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   auto *E =
       new (Buffer) CXXDynamicCastExpr(T, VK, K, Op, PathSize, WrittenTy, L,
                                       RParenLoc, AngleBrackets);
@@ -737,9 +731,7 @@ CXXDynamicCastExpr *CXXDynamicCastExpr::Create(const ASTContext &C, QualType T,
 
 CXXDynamicCastExpr *CXXDynamicCastExpr::CreateEmpty(const ASTContext &C,
                                                     unsigned PathSize) {
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   return new (Buffer) CXXDynamicCastExpr(EmptyShell(), PathSize);
 }
 
@@ -784,9 +776,7 @@ CXXReinterpretCastExpr::Create(const ASTContext &C, QualType T,
                                SourceLocation RParenLoc,
                                SourceRange AngleBrackets) {
   unsigned PathSize = (BasePath ? BasePath->size() : 0);
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   auto *E =
       new (Buffer) CXXReinterpretCastExpr(T, VK, K, Op, PathSize, WrittenTy, L,
                                           RParenLoc, AngleBrackets);
@@ -798,9 +788,7 @@ CXXReinterpretCastExpr::Create(const ASTContext &C, QualType T,
 
 CXXReinterpretCastExpr *
 CXXReinterpretCastExpr::CreateEmpty(const ASTContext &C, unsigned PathSize) {
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   return new (Buffer) CXXReinterpretCastExpr(EmptyShell(), PathSize);
 }
 
@@ -823,9 +811,7 @@ CXXFunctionalCastExpr::Create(const ASTContext &C, QualType T, ExprValueKind VK,
                               const CXXCastPath *BasePath,
                               SourceLocation L, SourceLocation R) {
   unsigned PathSize = (BasePath ? BasePath->size() : 0);
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   auto *E =
       new (Buffer) CXXFunctionalCastExpr(T, VK, Written, K, Op, PathSize, L, R);
   if (PathSize)
@@ -836,9 +822,7 @@ CXXFunctionalCastExpr::Create(const ASTContext &C, QualType T, ExprValueKind VK,
 
 CXXFunctionalCastExpr *
 CXXFunctionalCastExpr::CreateEmpty(const ASTContext &C, unsigned PathSize) {
-  void *Buffer =
-      C.Allocate(totalSizeToAlloc<CastExpr::BasePathSizeTy, CXXBaseSpecifier *>(
-          PathSize ? 1 : 0, PathSize));
+  void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
   return new (Buffer) CXXFunctionalCastExpr(EmptyShell(), PathSize);
 }