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LLVM Techniques, Tips, and Best Practices Clang and Middle-End Libraries

Name: LLVM Techniques, Tips, and Best Practices Clang and Middle-End Libraries
Author: Min-Yih Hsu
ISBN: 9781838824952

by Min-Yih Hsu

April 2021

Intermediate to advanced

370 pages

7h 34m

English

Packt Publishing

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LLVM Techniques, Tips, and Best Practices Clang and Middle-End Libraries
ContributorsAbout the authorAbout the reviewer
Preface
Who this book is forWhat this book coversTo get the most out of this bookDownload the example code filesDownload the color imagesConventions usedGet in touchReviews
Section 1: Build System and LLVM-Specific Tooling
Chapter 1: Saving Resources When Building LLVM
Technical requirementsCutting down building resources with better toolingReplacing GNU Make with NinjaAvoiding the use of the BFD linkerTweaking CMake argumentsChoosing the right build typeAvoiding building all targetsBuilding as shared librariesSplitting the debug infoBuilding an optimized version of llvm-tblgenUsing the new PassManager and ClangUsing GN for a faster turnaround timeSummaryFurther reading
Chapter 2: Exploring LLVM's Build System Features
Technical requirementsExploring a glossary of LLVM's important CMake directivesUsing the CMake function to add new librariesUsing the CMake function to add executables and toolsUsing the CMake function to add Pass pluginsUnderstanding CMake integration for out-of-tree projectsSummary
Chapter 3: Testing with LLVM LIT
Technical requirementsUsing LIT in out-of-tree projectsPreparing for our example project Writing LIT configurationsLIT internalsLearning useful FileCheck tricksPreparing for our example projectWriting FileCheck directivesExploring the TestSuite frameworkPreparing for our example projectImporting code into llvm-test-suiteSummaryFurther reading
Chapter 4: TableGen Development
Technical requirementsIntroduction to TableGen syntaxLayout and recordsBang operatorsMulticlassThe DAG data typeWriting a donut recipe in TableGenPrinting a recipe via the TableGen backendTableGen's high-level workflowWriting the TableGen backendIntegrating the RecipePrinter TableGen backendSummaryFurther reading
Section 2: Frontend Development
Chapter 5: Exploring Clang's Architecture
Technical requirementsLearning Clang's subsystems and their rolesDriverLLVM, assemblers, and linkersExploring Clang's tooling features and extension optionsThe FrontendAction classClang pluginsLibTooling and Clang ToolsSummaryFurther reading
Chapter 6: Extending the Preprocessor
Technical requirementsWorking with SourceLocation and SourceManagerIntroducing SourceLocationIntroducing SourceManagerLearning preprocessor and lexer essentialsUnderstanding the role of the preprocessor and lexer in ClangUnderstanding TokenHandling macrosDeveloping custom preprocessor plugins and callbacksThe project goal and preparationImplementing a custom pragma handlerImplementing custom preprocessor callbacksSummaryExercises

Chapter 7: Handling AST
Technical requirementsLearning about AST in ClangIn-memory structure of Clang ASTTypes in Clang ASTASTMatcherWriting AST pluginsProject overviewPrinting diagnostic messagesCreating the AST pluginSummary
Chapter 8: Working with Compiler Flags and Toolchains
Technical requirementsUnderstanding drivers and toolchains in ClangAdding custom driver flagsProject overviewDeclaring custom driver flagsTranslating custom driver flagsPassing flags to the frontendAdding a custom toolchainProject overviewCreating the toolchain and adding a custom include pathCreating a custom assembling stageCreating a custom linking stageVerifying the custom toolchainSummaryExercises
Section 3: "Middle-End" Development
Chapter 9: Working with PassManager and AnalysisManager
Technical requirementsWriting an LLVM Pass for the new PassManagerProject overviewWriting the StrictOpt PassWorking with the new AnalysisManagerOverview of the projectWriting the HaltAnalyzer PassLearning instrumentations in the new PassManagerPrinting Pass pipeline detailsPrinting changes to the IR after each PassBisecting the Pass pipelineSummaryQuestions
Chapter 10: Processing LLVM IR
Technical requirementsLearning LLVM IR basicsIterating different IR unitsIterating instructionsIterating basic blocksIterating the call graphLearning about GraphTraitsWorking with values and instructionsUnderstanding SSAWorking with valuesWorking with instructionsWorking with loopsLearning about loop representation in LLVMLearning about loop infrastructure in LLVMSummary
Chapter 11: Gearing Up with Support Utilities
Technical requirementsPrinting diagnostic messagesCollecting statisticsUsing the Statistic classUsing an optimization remarkAdding time measurementsUsing the Timer classCollecting the time traceError-handling utilities in LLVMIntroducing the Error classLearning about the Expected and ErrorOr classesThe Expected classThe ErrorOr classSummary
Chapter 12: Learning LLVM IR Instrumentation
Technical requirementsDeveloping a sanitizerAn example of using an address sanitizerCreating a loop counter sanitizerWorking with PGOIntroduction to instrumentation-based PGOIntroduction to sampling-based PGOUsing profiling data analysesSummary
Assessments
Chapter 6, Extending the PreprocessorChapter 8, Working with Compiler Flags and ToolchainsChapter 9, Working with PassManager and AnalysisManager
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Content preview from LLVM Techniques, Tips, and Best Practices Clang and Middle-End Libraries

Chapter 6: Extending the Preprocessor

In the previous chapter, we went through the structure of Clang—the official frontend of Low-Level Virtual Machine (LLVM) for C-family languages—and some of its most important components. We also introduced a variety of Clang's tooling and extension options. In this chapter, we're diving into the first phase in Clang's frontend pipeline: the preprocessor.

For C-family programming languages, preprocessing is an early compilation phase that replaces any directive starting with a hash (#) character—#include and #define, to name but a few—with some other textual contents (or non-textual tokens, in some rare cases). For example, the preprocessor will basically copy and paste contents of header files designated ...

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LLVM Techniques, Tips, and Best Practices Clang and Middle-End Libraries

by Min-Yih Hsu

Chapter 6: Extending the Preprocessor

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