0ffa29fe81
Clang uses timestamp files to track the last time an implicitly-built
PCM file was verified to be up-to-date with regard to its inputs. With
`-fbuild-session-{file,timestamp}=` and
`-fmodules-validate-once-per-build-session` this reduces the number of
times a PCM file is checked per "build session".
The behavior I'm seeing with the current scheme is that when lots of
Clang instances wait for the same PCM to be built, they race to validate
it as soon as the file lock gets released, causing lots of concurrent
IO.
This patch makes it so that the timestamp is written by the same Clang
instance responsible for building the PCM while still holding the lock.
This makes it so that whenever a PCM file gets compiled, it's never
re-validated in the same build session.
I believe this is as sound as the current scheme. One thing to be aware
of is that there might be a time interval between accessing input file N
and writing the timestamp file, where changes to input files 0..<N would
not result in a rebuild. Since this is the case current scheme too, I'm
not too concerned about that.
I've seen this speed up `clang-scan-deps` by ~27%.
111 lines
4.0 KiB
C++
111 lines
4.0 KiB
C++
//===- ASTCommon.h - Common stuff for ASTReader/ASTWriter -*- C++ -*-=========//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines common functions that both ASTReader and ASTWriter use.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CLANG_LIB_SERIALIZATION_ASTCOMMON_H
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#define LLVM_CLANG_LIB_SERIALIZATION_ASTCOMMON_H
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#include "clang/AST/ASTContext.h"
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#include "clang/AST/DeclFriend.h"
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#include "clang/Basic/LLVM.h"
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#include "clang/Serialization/ASTBitCodes.h"
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namespace clang {
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namespace serialization {
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enum DeclUpdateKind {
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UPD_CXX_ADDED_IMPLICIT_MEMBER,
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UPD_CXX_ADDED_TEMPLATE_SPECIALIZATION,
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UPD_CXX_ADDED_ANONYMOUS_NAMESPACE,
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UPD_CXX_ADDED_FUNCTION_DEFINITION,
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UPD_CXX_ADDED_VAR_DEFINITION,
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UPD_CXX_POINT_OF_INSTANTIATION,
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UPD_CXX_INSTANTIATED_CLASS_DEFINITION,
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UPD_CXX_INSTANTIATED_DEFAULT_ARGUMENT,
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UPD_CXX_INSTANTIATED_DEFAULT_MEMBER_INITIALIZER,
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UPD_CXX_RESOLVED_DTOR_DELETE,
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UPD_CXX_RESOLVED_EXCEPTION_SPEC,
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UPD_CXX_DEDUCED_RETURN_TYPE,
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UPD_DECL_MARKED_USED,
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UPD_MANGLING_NUMBER,
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UPD_STATIC_LOCAL_NUMBER,
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UPD_DECL_MARKED_OPENMP_THREADPRIVATE,
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UPD_DECL_MARKED_OPENMP_ALLOCATE,
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UPD_DECL_MARKED_OPENMP_DECLARETARGET,
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UPD_DECL_EXPORTED,
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UPD_ADDED_ATTR_TO_RECORD
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};
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TypeIdx TypeIdxFromBuiltin(const BuiltinType *BT);
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unsigned ComputeHash(Selector Sel);
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/// Retrieve the "definitive" declaration that provides all of the
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/// visible entries for the given declaration context, if there is one.
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///
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/// The "definitive" declaration is the only place where we need to look to
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/// find information about the declarations within the given declaration
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/// context. For example, C++ and Objective-C classes, C structs/unions, and
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/// Objective-C protocols, categories, and extensions are all defined in a
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/// single place in the source code, so they have definitive declarations
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/// associated with them. C++ namespaces, on the other hand, can have
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/// multiple definitions.
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const DeclContext *getDefinitiveDeclContext(const DeclContext *DC);
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/// Determine whether the given declaration kind is redeclarable.
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bool isRedeclarableDeclKind(unsigned Kind);
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/// Determine whether the given declaration needs an anonymous
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/// declaration number.
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bool needsAnonymousDeclarationNumber(const NamedDecl *D);
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/// Visit each declaration within \c DC that needs an anonymous
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/// declaration number and call \p Visit with the declaration and its number.
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template<typename Fn> void numberAnonymousDeclsWithin(const DeclContext *DC,
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Fn Visit) {
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unsigned Index = 0;
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for (Decl *LexicalD : DC->decls()) {
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// For a friend decl, we care about the declaration within it, if any.
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if (auto *FD = dyn_cast<FriendDecl>(LexicalD))
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LexicalD = FD->getFriendDecl();
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auto *ND = dyn_cast_or_null<NamedDecl>(LexicalD);
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if (!ND || !needsAnonymousDeclarationNumber(ND))
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continue;
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Visit(ND, Index++);
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}
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}
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/// Determine whether the given declaration will be included in the per-module
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/// initializer if it needs to be eagerly handed to the AST consumer. If so, we
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/// should not hand it to the consumer when deserializing it, nor include it in
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/// the list of eagerly deserialized declarations.
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inline bool isPartOfPerModuleInitializer(const Decl *D) {
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if (isa<ImportDecl>(D))
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return true;
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// Template instantiations are notionally in an "instantiation unit" rather
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// than in any particular translation unit, so they need not be part of any
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// particular (sub)module's per-module initializer.
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if (auto *VD = dyn_cast<VarDecl>(D))
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return !isTemplateInstantiation(VD->getTemplateSpecializationKind());
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return false;
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}
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void updateModuleTimestamp(StringRef ModuleFilename);
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} // namespace serialization
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} // namespace clang
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#endif
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