riccibruno created this revision.
riccibruno added reviewers: rsmith, rjmccall, erichkeane.
riccibruno added a project: clang.
Herald added a subscriber: cfe-commits.
The `TagDecl *OwnedTagDecl` in `ElaboratedType` is quite commonly
null (at least when parsing all of Boost, it is non-null for only about 600
of the 66k `ElaboratedType`). Therefore we can save a pointer in the
common case by storing it as a trailing object, and storing a bit in the
bit-fields of Type indicating when pointer is null.
Repository:
rC Clang
https://reviews.llvm.org/D50715
Files:
include/clang/AST/Type.h
lib/AST/ASTContext.cpp
Index: lib/AST/ASTContext.cpp
===================================================================
--- lib/AST/ASTContext.cpp
+++ lib/AST/ASTContext.cpp
@@ -4133,8 +4133,10 @@
(void)CheckT;
}
- T = new (*this, TypeAlignment)
- ElaboratedType(Keyword, NNS, NamedType, Canon, OwnedTagDecl);
+ void *Mem = Allocate(ElaboratedType::totalSizeToAlloc<TagDecl *>(!!OwnedTagDecl),
+ TypeAlignment);
+ T = new (Mem) ElaboratedType(Keyword, NNS, NamedType, Canon, OwnedTagDecl);
+
Types.push_back(T);
ElaboratedTypes.InsertNode(T, InsertPos);
return QualType(T, 0);
Index: include/clang/AST/Type.h
===================================================================
--- include/clang/AST/Type.h
+++ include/clang/AST/Type.h
@@ -45,6 +45,7 @@
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/PointerLikeTypeTraits.h"
#include "llvm/Support/type_traits.h"
+#include "llvm/Support/TrailingObjects.h"
#include <cassert>
#include <cstddef>
#include <cstdint>
@@ -1591,6 +1592,16 @@
enum { NumTypeWithKeywordBits = 8 };
+ class ElaboratedTypeBitfields {
+ friend class ElaboratedType;
+
+ unsigned : NumTypeBits;
+ unsigned : NumTypeWithKeywordBits;
+
+ /// Whether the ElaboratedType has a trailing OwnedTagDecl.
+ unsigned HasOwnedTagDecl : 1;
+ };
+
class VectorTypeBitfields {
friend class VectorType;
friend class DependentVectorType;
@@ -1687,6 +1698,7 @@
ObjCObjectTypeBitfields ObjCObjectTypeBits;
ReferenceTypeBitfields ReferenceTypeBits;
TypeWithKeywordBitfields TypeWithKeywordBits;
+ ElaboratedTypeBitfields ElaboratedTypeBits;
VectorTypeBitfields VectorTypeBits;
SubstTemplateTypeParmPackTypeBitfields SubstTemplateTypeParmPackTypeBits;
TemplateSpecializationTypeBitfields TemplateSpecializationTypeBits;
@@ -1712,6 +1724,8 @@
"ReferenceTypeBitfields is larger than 8 bytes!");
static_assert(sizeof(TypeWithKeywordBitfields) <= 8,
"TypeWithKeywordBitfields is larger than 8 bytes!");
+ static_assert(sizeof(ElaboratedTypeBitfields) <= 8,
+ "ElaboratedTypeBitfields is larger than 8 bytes!");
static_assert(sizeof(VectorTypeBitfields) <= 8,
"VectorTypeBitfields is larger than 8 bytes!");
static_assert(sizeof(SubstTemplateTypeParmPackTypeBitfields) <= 8,
@@ -5015,35 +5029,42 @@
/// source code, including tag keywords and any nested-name-specifiers.
/// The type itself is always "sugar", used to express what was written
/// in the source code but containing no additional semantic information.
-class ElaboratedType : public TypeWithKeyword, public llvm::FoldingSetNode {
+class ElaboratedType final
+ : public TypeWithKeyword,
+ public llvm::FoldingSetNode,
+ private llvm::TrailingObjects<ElaboratedType, TagDecl *> {
friend class ASTContext; // ASTContext creates these
+ friend TrailingObjects;
/// The nested name specifier containing the qualifier.
NestedNameSpecifier *NNS;
/// The type that this qualified name refers to.
QualType NamedType;
- /// The (re)declaration of this tag type owned by this occurrence, or nullptr
- /// if none.
- TagDecl *OwnedTagDecl;
+ /// The (re)declaration of this tag type owned by this occurrence is stored
+ /// as a trailing object if there is one. Use getOwnedTagDecl to obtain
+ /// it, or obtain a null pointer if there is none.
ElaboratedType(ElaboratedTypeKeyword Keyword, NestedNameSpecifier *NNS,
QualType NamedType, QualType CanonType, TagDecl *OwnedTagDecl)
- : TypeWithKeyword(Keyword, Elaborated, CanonType,
- NamedType->isDependentType(),
- NamedType->isInstantiationDependentType(),
- NamedType->isVariablyModifiedType(),
- NamedType->containsUnexpandedParameterPack()),
- NNS(NNS), NamedType(NamedType), OwnedTagDecl(OwnedTagDecl) {
+ : TypeWithKeyword(Keyword, Elaborated, CanonType,
+ NamedType->isDependentType(),
+ NamedType->isInstantiationDependentType(),
+ NamedType->isVariablyModifiedType(),
+ NamedType->containsUnexpandedParameterPack()),
+ NNS(NNS), NamedType(NamedType) {
+ ElaboratedTypeBits.HasOwnedTagDecl = false;
+ if (OwnedTagDecl) {
+ ElaboratedTypeBits.HasOwnedTagDecl = true;
+ *getTrailingObjects<TagDecl *>() = OwnedTagDecl;
+ }
assert(!(Keyword == ETK_None && NNS == nullptr) &&
"ElaboratedType cannot have elaborated type keyword "
"and name qualifier both null.");
}
public:
- ~ElaboratedType();
-
/// Retrieve the qualification on this type.
NestedNameSpecifier *getQualifier() const { return NNS; }
@@ -5057,11 +5078,14 @@
bool isSugared() const { return true; }
/// Return the (re)declaration of this type owned by this occurrence of this
- /// type, or nullptr if none.
- TagDecl *getOwnedTagDecl() const { return OwnedTagDecl; }
+ /// type, or nullptr if there is none.
+ TagDecl *getOwnedTagDecl() const {
+ return ElaboratedTypeBits.HasOwnedTagDecl ? *getTrailingObjects<TagDecl *>()
+ : nullptr;
+ }
void Profile(llvm::FoldingSetNodeID &ID) {
- Profile(ID, getKeyword(), NNS, NamedType, OwnedTagDecl);
+ Profile(ID, getKeyword(), NNS, NamedType, getOwnedTagDecl());
}
static void Profile(llvm::FoldingSetNodeID &ID, ElaboratedTypeKeyword Keyword,
@@ -5073,9 +5097,7 @@
ID.AddPointer(OwnedTagDecl);
}
- static bool classof(const Type *T) {
- return T->getTypeClass() == Elaborated;
- }
+ static bool classof(const Type *T) { return T->getTypeClass() == Elaborated; }
};
/// Represents a qualified type name for which the type name is
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