[clang] 5d8d3a1 - [NFC] Increase initial size of FoldingSets used in ASTContext and CodeGenTypes

[Dawid Jurczak via cfe-commits]

Author: Dawid Jurczak
Date: 2022-02-08T17:54:04+01:00
New Revision: 5d8d3a11c4d4ed8bb610f60f8fa37b8043a40acd

URL: https://github.com/llvm/llvm-project/commit/5d8d3a11c4d4ed8bb610f60f8fa37b8043a40acd
DIFF: https://github.com/llvm/llvm-project/commit/5d8d3a11c4d4ed8bb610f60f8fa37b8043a40acd.diff

LOG: [NFC] Increase initial size of FoldingSets used in ASTContext and CodeGenTypes

Among many FoldingSet users most notable seem to be ASTContext and CodeGenTypes.
The reasons that we spend not-so-tiny amount of time in FoldingSet calls from there, are following:

  1. Default FoldingSet capacity for 2^6 items very often is not enough.
     For PointerTypes/ElaboratedTypes/ParenTypes it's not unlikely to observe growing it to 256 or 512 items.
     FunctionProtoTypes can easily exceed 1k items capacity growing up to 4k or even 8k size.

  2. FoldingSetBase::GrowBucketCount cost itself is not very bad (pure reallocations are rather cheap thanks to BumpPtrAllocator).
     What matters is high collision rate when lot of items end up in same bucket slowing down FoldingSetBase::FindNodeOrInsertPos and trashing CPU cache
     (as items with same hash are organized in intrusive linked list which need to be traversed).

This change address both issues by increasing initial size of FoldingSets used in ASTContext and CodeGenTypes.

Extracted from: https://reviews.llvm.org/D118385

Differential Revision: https://reviews.llvm.org/D118608

Added: 
    

Modified: 
    clang/include/clang/AST/ASTContext.h
    clang/lib/AST/ASTContext.cpp
    clang/lib/CodeGen/CodeGenTypes.h

Removed: 
    


################################################################################
diff  --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index 63c11e237d6c8..510c63962053b 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -211,7 +211,7 @@ class ASTContext : public RefCountedBase<ASTContext> {
   mutable SmallVector<Type *, 0> Types;
   mutable llvm::FoldingSet<ExtQuals> ExtQualNodes;
   mutable llvm::FoldingSet<ComplexType> ComplexTypes;
-  mutable llvm::FoldingSet<PointerType> PointerTypes;
+  mutable llvm::FoldingSet<PointerType> PointerTypes{GeneralTypesLog2InitSize};
   mutable llvm::FoldingSet<AdjustedType> AdjustedTypes;
   mutable llvm::FoldingSet<BlockPointerType> BlockPointerTypes;
   mutable llvm::FoldingSet<LValueReferenceType> LValueReferenceTypes;
@@ -243,9 +243,10 @@ class ASTContext : public RefCountedBase<ASTContext> {
     SubstTemplateTypeParmPackTypes;
   mutable llvm::ContextualFoldingSet<TemplateSpecializationType, ASTContext&>
     TemplateSpecializationTypes;
-  mutable llvm::FoldingSet<ParenType> ParenTypes;
+  mutable llvm::FoldingSet<ParenType> ParenTypes{GeneralTypesLog2InitSize};
   mutable llvm::FoldingSet<UsingType> UsingTypes;
-  mutable llvm::FoldingSet<ElaboratedType> ElaboratedTypes;
+  mutable llvm::FoldingSet<ElaboratedType> ElaboratedTypes{
+      GeneralTypesLog2InitSize};
   mutable llvm::FoldingSet<DependentNameType> DependentNameTypes;
   mutable llvm::ContextualFoldingSet<DependentTemplateSpecializationType,
                                      ASTContext&>
@@ -466,6 +467,10 @@ class ASTContext : public RefCountedBase<ASTContext> {
   };
   llvm::DenseMap<Module*, PerModuleInitializers*> ModuleInitializers;
 
+  static constexpr unsigned ConstantArrayTypesLog2InitSize = 8;
+  static constexpr unsigned GeneralTypesLog2InitSize = 9;
+  static constexpr unsigned FunctionProtoTypesLog2InitSize = 12;
+
   ASTContext &this_() { return *this; }
 
 public:

diff  --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index f2ac57465398b..527c8b56159e0 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -973,7 +973,8 @@ static bool isAddrSpaceMapManglingEnabled(const TargetInfo &TI,
 ASTContext::ASTContext(LangOptions &LOpts, SourceManager &SM,
                        IdentifierTable &idents, SelectorTable &sels,
                        Builtin::Context &builtins, TranslationUnitKind TUKind)
-    : ConstantArrayTypes(this_()), FunctionProtoTypes(this_()),
+    : ConstantArrayTypes(this_(), ConstantArrayTypesLog2InitSize),
+      FunctionProtoTypes(this_(), FunctionProtoTypesLog2InitSize),
       TemplateSpecializationTypes(this_()),
       DependentTemplateSpecializationTypes(this_()), AutoTypes(this_()),
       SubstTemplateTemplateParmPacks(this_()),

diff  --git a/clang/lib/CodeGen/CodeGenTypes.h b/clang/lib/CodeGen/CodeGenTypes.h
index 28b8312229439..05aae88ba59ed 100644
--- a/clang/lib/CodeGen/CodeGenTypes.h
+++ b/clang/lib/CodeGen/CodeGenTypes.h
@@ -76,7 +76,7 @@ class CodeGenTypes {
   llvm::DenseMap<const Type*, llvm::StructType *> RecordDeclTypes;
 
   /// Hold memoized CGFunctionInfo results.
-  llvm::FoldingSet<CGFunctionInfo> FunctionInfos;
+  llvm::FoldingSet<CGFunctionInfo> FunctionInfos{FunctionInfosLog2InitSize};
 
   /// This set keeps track of records that we're currently converting
   /// to an IR type.  For example, when converting:
@@ -98,6 +98,7 @@ class CodeGenTypes {
 
   llvm::SmallSet<const Type *, 8> RecordsWithOpaqueMemberPointers;
 
+  static constexpr unsigned FunctionInfosLog2InitSize = 9;
   /// Helper for ConvertType.
   llvm::Type *ConvertFunctionTypeInternal(QualType FT);