arphaman created this revision. arphaman added reviewers: ravikandhadai, egorzhdan, aaron.ballman, rsmith. Herald added subscribers: ributzka, kristof.beyls, mgorny. arphaman requested review of this revision.
Recently we observed high memory pressure caused by clang during some parallel builds. We discovered that we have several projects that have a large number of `#define` directives in their TUs (on the order of millions), which caused huge memory consumption in clang due to a lot of allocations for `MacroInfo`. We would like to reduce the memory overhead of clang for a single `#define` to reduce the memory overhead for these files, to allow us to reduce the memory pressure on the system during highly parallel builds. This change achieves that by removing the `SmallVector` in `MacroInfo` and instead storing the tokens in an array allocated using the bump pointer allocator, after all tokens are lexed. The added unit test with 1000000 `#define` directives illustrates the problem. Prior to this change, on arm64 macOS, clang's PP bump pointer allocator allocated 272007616 bytes, and used roughly 272 bytes per `#define`. After this change, clang's PP bump pointer allocator allocates 120002016 bytes, and uses only roughly 120 bytes per `#define`. For an example test file that we have internally with 7.8 million `#define` directives, this change produces the following improvement on arm64 macOS: Persistent allocation footprint for this test case file as it's being compiled to LLVM IR went down 22% from 5.28 GB to 4.07 GB and the total allocations went down 14% from 8.26 GB to 7.05 GB. Furthermore, this change reduced the total number of allocations made by the system for this clang invocation from 1454853 to 133663, an order of magnitude improvement. https://reviews.llvm.org/D117348 Files: clang/include/clang/Lex/MacroInfo.h clang/lib/Lex/MacroInfo.cpp clang/lib/Lex/PPDirectives.cpp clang/lib/Serialization/ASTReader.cpp clang/lib/Serialization/ASTWriter.cpp clang/unittests/Lex/CMakeLists.txt clang/unittests/Lex/PPMemoryAllocationsTest.cpp
Index: clang/unittests/Lex/PPMemoryAllocationsTest.cpp =================================================================== --- /dev/null +++ clang/unittests/Lex/PPMemoryAllocationsTest.cpp @@ -0,0 +1,97 @@ +//===- unittests/Lex/PPMemoryAllocationsTest.cpp - ----------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===--------------------------------------------------------------===// + +#include "clang/Basic/Diagnostic.h" +#include "clang/Basic/DiagnosticOptions.h" +#include "clang/Basic/FileManager.h" +#include "clang/Basic/LangOptions.h" +#include "clang/Basic/SourceManager.h" +#include "clang/Basic/TargetInfo.h" +#include "clang/Basic/TargetOptions.h" +#include "clang/Lex/HeaderSearch.h" +#include "clang/Lex/HeaderSearchOptions.h" +#include "clang/Lex/ModuleLoader.h" +#include "clang/Lex/Preprocessor.h" +#include "clang/Lex/PreprocessorOptions.h" +#include "gtest/gtest.h" + +using namespace clang; + +namespace { + +class PPMemoryAllocationsTest : public ::testing::Test { +protected: + PPMemoryAllocationsTest() + : FileMgr(FileMgrOpts), DiagID(new DiagnosticIDs()), + Diags(DiagID, new DiagnosticOptions, new IgnoringDiagConsumer()), + SourceMgr(Diags, FileMgr), TargetOpts(new TargetOptions) { + TargetOpts->Triple = "x86_64-apple-darwin11.1.0"; + Target = TargetInfo::CreateTargetInfo(Diags, TargetOpts); + } + + FileSystemOptions FileMgrOpts; + FileManager FileMgr; + IntrusiveRefCntPtr<DiagnosticIDs> DiagID; + DiagnosticsEngine Diags; + SourceManager SourceMgr; + LangOptions LangOpts; + std::shared_ptr<TargetOptions> TargetOpts; + IntrusiveRefCntPtr<TargetInfo> Target; +}; + +TEST_F(PPMemoryAllocationsTest, PPMacroDefinesAllocations) { + std::string Source; + size_t NumMacros = 1000000; + { + llvm::raw_string_ostream SourceOS(Source); + + // Create a combination of 1 or 3 token macros. + for (size_t I = 0; I < NumMacros; ++I) { + SourceOS << "#define MACRO_ID_" << I << " "; + if ((I % 2) == 0) + SourceOS << "(" << I << ")"; + else + SourceOS << I; + SourceOS << "\n"; + } + } + + std::unique_ptr<llvm::MemoryBuffer> Buf = + llvm::MemoryBuffer::getMemBuffer(Source); + SourceMgr.setMainFileID(SourceMgr.createFileID(std::move(Buf))); + + TrivialModuleLoader ModLoader; + HeaderSearch HeaderInfo(std::make_shared<HeaderSearchOptions>(), SourceMgr, + Diags, LangOpts, Target.get()); + Preprocessor PP(std::make_shared<PreprocessorOptions>(), Diags, LangOpts, + SourceMgr, HeaderInfo, ModLoader, + /*IILookup =*/nullptr, + /*OwnsHeaderSearch =*/false); + PP.Initialize(*Target); + PP.EnterMainSourceFile(); + + while (1) { + Token tok; + PP.Lex(tok); + if (tok.is(tok::eof)) + break; + } + + size_t NumAllocated = PP.getPreprocessorAllocator().getBytesAllocated(); + float BytesPerDefine = float(NumAllocated) / float(NumMacros); + llvm::errs() << "Num preprocessor allocations for " << NumMacros + << " #define: " << NumAllocated << "\n"; + llvm::errs() << "Bytes per #define: " << BytesPerDefine << "\n"; + // On arm64-apple-macos, we get around 120 bytes per define. + // Assume a reasonable upper bound based on that number that we don't want + // to exceed when storing information about a macro #define with 1 or 3 + // tokens. + EXPECT_LT(BytesPerDefine, 130.0f); +} + +} // anonymous namespace Index: clang/unittests/Lex/CMakeLists.txt =================================================================== --- clang/unittests/Lex/CMakeLists.txt +++ clang/unittests/Lex/CMakeLists.txt @@ -9,6 +9,7 @@ LexerTest.cpp PPCallbacksTest.cpp PPConditionalDirectiveRecordTest.cpp + PPMemoryAllocationsTest.cpp ) clang_target_link_libraries(LexTests Index: clang/lib/Serialization/ASTWriter.cpp =================================================================== --- clang/lib/Serialization/ASTWriter.cpp +++ clang/lib/Serialization/ASTWriter.cpp @@ -2405,6 +2405,7 @@ AddSourceLocation(MI->getDefinitionEndLoc(), Record); Record.push_back(MI->isUsed()); Record.push_back(MI->isUsedForHeaderGuard()); + Record.push_back(MI->getNumTokens()); unsigned Code; if (MI->isObjectLike()) { Code = PP_MACRO_OBJECT_LIKE; Index: clang/lib/Serialization/ASTReader.cpp =================================================================== --- clang/lib/Serialization/ASTReader.cpp +++ clang/lib/Serialization/ASTReader.cpp @@ -1694,6 +1694,7 @@ RecordData Record; SmallVector<IdentifierInfo*, 16> MacroParams; MacroInfo *Macro = nullptr; + llvm::MutableArrayRef<Token> MacroTokens; while (true) { // Advance to the next record, but if we get to the end of the block, don't @@ -1748,7 +1749,8 @@ MI->setDefinitionEndLoc(ReadSourceLocation(F, Record, NextIndex)); MI->setIsUsed(Record[NextIndex++]); MI->setUsedForHeaderGuard(Record[NextIndex++]); - + MacroTokens = MI->allocateTokens(Record[NextIndex++], + PP.getPreprocessorAllocator()); if (RecType == PP_MACRO_FUNCTION_LIKE) { // Decode function-like macro info. bool isC99VarArgs = Record[NextIndex++]; @@ -1793,10 +1795,14 @@ // If we see a TOKEN before a PP_MACRO_*, then the file is // erroneous, just pretend we didn't see this. if (!Macro) break; + if (MacroTokens.empty()) { + Error("unexpected number of macro tokens for a macro in AST file"); + return Macro; + } unsigned Idx = 0; - Token Tok = ReadToken(F, Record, Idx); - Macro->AddTokenToBody(Tok); + MacroTokens[0] = ReadToken(F, Record, Idx); + MacroTokens = MacroTokens.drop_front(); break; } } Index: clang/lib/Lex/PPDirectives.cpp =================================================================== --- clang/lib/Lex/PPDirectives.cpp +++ clang/lib/Lex/PPDirectives.cpp @@ -2708,12 +2708,14 @@ if (!Tok.is(tok::eod)) LastTok = Tok; + SmallVector<Token, 16> Tokens; + // Read the rest of the macro body. if (MI->isObjectLike()) { // Object-like macros are very simple, just read their body. while (Tok.isNot(tok::eod)) { LastTok = Tok; - MI->AddTokenToBody(Tok); + Tokens.push_back(Tok); // Get the next token of the macro. LexUnexpandedToken(Tok); } @@ -2728,7 +2730,7 @@ LastTok = Tok; if (!Tok.isOneOf(tok::hash, tok::hashat, tok::hashhash)) { - MI->AddTokenToBody(Tok); + Tokens.push_back(Tok); if (VAOCtx.isVAOptToken(Tok)) { // If we're already within a VAOPT, emit an error. @@ -2742,7 +2744,7 @@ Diag(Tok, diag::err_pp_missing_lparen_in_vaopt_use); return nullptr; } - MI->AddTokenToBody(Tok); + Tokens.push_back(Tok); VAOCtx.sawVAOptFollowedByOpeningParens(Tok.getLocation()); LexUnexpandedToken(Tok); if (Tok.is(tok::hashhash)) { @@ -2753,10 +2755,10 @@ } else if (VAOCtx.isInVAOpt()) { if (Tok.is(tok::r_paren)) { if (VAOCtx.sawClosingParen()) { - const unsigned NumTokens = MI->getNumTokens(); - assert(NumTokens >= 3 && "Must have seen at least __VA_OPT__( " - "and a subsequent tok::r_paren"); - if (MI->getReplacementToken(NumTokens - 2).is(tok::hashhash)) { + assert(Tokens.size() >= 3 && + "Must have seen at least __VA_OPT__( " + "and a subsequent tok::r_paren"); + if (Tokens[Tokens.size() - 2].is(tok::hashhash)) { Diag(Tok, diag::err_vaopt_paste_at_end); return nullptr; } @@ -2775,7 +2777,7 @@ // things. if (getLangOpts().TraditionalCPP) { Tok.setKind(tok::unknown); - MI->AddTokenToBody(Tok); + Tokens.push_back(Tok); // Get the next token of the macro. LexUnexpandedToken(Tok); @@ -2791,17 +2793,16 @@ LexUnexpandedToken(Tok); if (Tok.is(tok::eod)) { - MI->AddTokenToBody(LastTok); + Tokens.push_back(LastTok); break; } - unsigned NumTokens = MI->getNumTokens(); - if (NumTokens && Tok.getIdentifierInfo() == Ident__VA_ARGS__ && - MI->getReplacementToken(NumTokens-1).is(tok::comma)) + if (!Tokens.empty() && Tok.getIdentifierInfo() == Ident__VA_ARGS__ && + Tokens[Tokens.size() - 1].is(tok::comma)) MI->setHasCommaPasting(); // Things look ok, add the '##' token to the macro. - MI->AddTokenToBody(LastTok); + Tokens.push_back(LastTok); continue; } @@ -2820,7 +2821,7 @@ // confused. if (getLangOpts().AsmPreprocessor && Tok.isNot(tok::eod)) { LastTok.setKind(tok::unknown); - MI->AddTokenToBody(LastTok); + Tokens.push_back(LastTok); continue; } else { Diag(Tok, diag::err_pp_stringize_not_parameter) @@ -2830,13 +2831,13 @@ } // Things look ok, add the '#' and param name tokens to the macro. - MI->AddTokenToBody(LastTok); + Tokens.push_back(LastTok); // If the token following '#' is VAOPT, let the next iteration handle it // and check it for correctness, otherwise add the token and prime the // loop with the next one. if (!VAOCtx.isVAOptToken(Tok)) { - MI->AddTokenToBody(Tok); + Tokens.push_back(Tok); LastTok = Tok; // Get the next token of the macro. @@ -2852,6 +2853,8 @@ } } MI->setDefinitionEndLoc(LastTok.getLocation()); + + MI->setTokens(Tokens, BP); return MI; } /// HandleDefineDirective - Implements \#define. This consumes the entire macro @@ -3004,7 +3007,7 @@ Tok.startToken(); Tok.setKind(tok::kw__Static_assert); Tok.setIdentifierInfo(getIdentifierInfo("_Static_assert")); - MI->AddTokenToBody(Tok); + MI->appendToken(Tok, BP); (void)appendDefMacroDirective(getIdentifierInfo("static_assert"), MI); } } Index: clang/lib/Lex/MacroInfo.cpp =================================================================== --- clang/lib/Lex/MacroInfo.cpp +++ clang/lib/Lex/MacroInfo.cpp @@ -28,6 +28,23 @@ using namespace clang; +namespace { + +// MacroInfo is expected to take 40 bytes on platforms with an 8 byte pointer. +template <int> class MacroInfoSizeChecker { +public: + constexpr static bool AsExpected = true; +}; +template <> class MacroInfoSizeChecker<8> { +public: + constexpr static bool AsExpected = sizeof(MacroInfo) == 40; +}; + +static_assert(MacroInfoSizeChecker<sizeof(void *)>::AsExpected, + "Unexpected size of MacroInfo"); + +} // end namespace + MacroInfo::MacroInfo(SourceLocation DefLoc) : Location(DefLoc), IsDefinitionLengthCached(false), IsFunctionLike(false), IsC99Varargs(false), IsGNUVarargs(false), IsBuiltinMacro(false), @@ -39,6 +56,7 @@ assert(!IsDefinitionLengthCached); IsDefinitionLengthCached = true; + auto ReplacementTokens = tokens(); if (ReplacementTokens.empty()) return (DefinitionLength = 0); @@ -76,7 +94,7 @@ bool Lexically = !Syntactically; // Check # tokens in replacement, number of args, and various flags all match. - if (ReplacementTokens.size() != Other.ReplacementTokens.size() || + if (getNumTokens() != Other.getNumTokens() || getNumParams() != Other.getNumParams() || isFunctionLike() != Other.isFunctionLike() || isC99Varargs() != Other.isC99Varargs() || @@ -92,7 +110,7 @@ } // Check all the tokens. - for (unsigned i = 0, e = ReplacementTokens.size(); i != e; ++i) { + for (unsigned i = 0; i != NumReplacementTokens; ++i) { const Token &A = ReplacementTokens[i]; const Token &B = Other.ReplacementTokens[i]; if (A.getKind() != B.getKind()) @@ -157,7 +175,7 @@ } bool First = true; - for (const Token &Tok : ReplacementTokens) { + for (const Token &Tok : tokens()) { // Leading space is semantically meaningful in a macro definition, // so preserve it in the dump output. if (First || Tok.hasLeadingSpace()) Index: clang/include/clang/Lex/MacroInfo.h =================================================================== --- clang/include/clang/Lex/MacroInfo.h +++ clang/include/clang/Lex/MacroInfo.h @@ -54,11 +54,14 @@ /// macro, this includes the \c __VA_ARGS__ identifier on the list. IdentifierInfo **ParameterList = nullptr; + /// This is the list of tokens that the macro is defined to. + const Token *ReplacementTokens = nullptr; + /// \see ParameterList unsigned NumParameters = 0; - /// This is the list of tokens that the macro is defined to. - SmallVector<Token, 8> ReplacementTokens; + /// \see ReplacementTokens + unsigned NumReplacementTokens = 0; /// Length in characters of the macro definition. mutable unsigned DefinitionLength; @@ -230,26 +233,58 @@ bool isWarnIfUnused() const { return IsWarnIfUnused; } /// Return the number of tokens that this macro expands to. - unsigned getNumTokens() const { return ReplacementTokens.size(); } + unsigned getNumTokens() const { return NumReplacementTokens; } const Token &getReplacementToken(unsigned Tok) const { - assert(Tok < ReplacementTokens.size() && "Invalid token #"); + assert(Tok < NumReplacementTokens && "Invalid token #"); return ReplacementTokens[Tok]; } - using tokens_iterator = SmallVectorImpl<Token>::const_iterator; + using tokens_iterator = const Token *; + + tokens_iterator tokens_begin() const { return ReplacementTokens; } + tokens_iterator tokens_end() const { + return ReplacementTokens + NumReplacementTokens; + } + bool tokens_empty() const { return NumReplacementTokens == 0; } + ArrayRef<Token> tokens() const { + return llvm::makeArrayRef(ReplacementTokens, NumReplacementTokens); + } + + llvm::MutableArrayRef<Token> + allocateTokens(unsigned NumTokens, llvm::BumpPtrAllocator &PPAllocator) { + NumReplacementTokens = NumTokens; + Token *NewReplacementTokens = PPAllocator.Allocate<Token>(NumTokens); + ReplacementTokens = NewReplacementTokens; + return llvm::makeMutableArrayRef(NewReplacementTokens, NumTokens); + } - tokens_iterator tokens_begin() const { return ReplacementTokens.begin(); } - tokens_iterator tokens_end() const { return ReplacementTokens.end(); } - bool tokens_empty() const { return ReplacementTokens.empty(); } - ArrayRef<Token> tokens() const { return ReplacementTokens; } + void setTokens(ArrayRef<Token> Tokens, llvm::BumpPtrAllocator &PPAllocator) { + assert( + !IsDefinitionLengthCached && + "Changing replacement tokens after definition length got calculated"); + assert(ReplacementTokens == nullptr && NumReplacementTokens == 0 && + "Token list already set!"); + if (Tokens.empty()) + return; + + NumReplacementTokens = Tokens.size(); + Token *NewReplacementTokens = PPAllocator.Allocate<Token>(Tokens.size()); + std::copy(Tokens.begin(), Tokens.end(), NewReplacementTokens); + ReplacementTokens = NewReplacementTokens; + } - /// Add the specified token to the replacement text for the macro. - void AddTokenToBody(const Token &Tok) { + void appendToken(const Token &Tok, llvm::BumpPtrAllocator &PPAllocator) { assert( !IsDefinitionLengthCached && "Changing replacement tokens after definition length got calculated"); - ReplacementTokens.push_back(Tok); + Token *NewReplacementToks = + PPAllocator.Allocate<Token>(NumReplacementTokens + 1); + std::copy(ReplacementTokens, ReplacementTokens + NumReplacementTokens, + NewReplacementToks); + NewReplacementToks[NumReplacementTokens] = Tok; + NumReplacementTokens += 1; + ReplacementTokens = NewReplacementToks; } /// Return true if this macro is enabled.
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