Overview • The process of building a program • What a translation unit (TU) is, and its relationship to the code you write • The phases of translation • Declarations, definitions, and linkage • The one-definition compilation process translation • In C++, translation is performed upon a translation unit (TU) in nine well- defined stages • Evocatively named Phases 1 through 9 • A translation unit is defined (roughly) The Structure of a Program 20Copyright © 2020 Bob Steagall K E W B C O M P U T I N G Phases of Translation 21 CppCon 2020 - The Structure of a Program Phase 1 Phase 2 Phase 3 Phase 4 Phase 5 Phase

lambda functionsCppCon 2021 – Back to Basics: Templates – Part 1 Copyright © 2021 Bob Steagall Translation Units • Compilation • The process of converting human-readable source code into binary object standard calls the compilation process translation 25CppCon 2021 – Back to Basics: Templates – Part 1 Copyright © 2021 Bob Steagall Translation Units • In C++, translation is performed in nine well-defined These are what we usually refer to as pre-processing • The output of Phase 6 is a translation unit • A translation unit is defined [5.1] as • A source file • Plus all the headers and source files included

In this talk I'll tell you about C++ AoT compiler, JiTs for dynamic language, JiTs for binary translation, and dive back 20, 30, 40, 50, 60 years, way back into compiler history and read wonderful academic “just-in-time” compilation (JiT) techniques since the 1960s. Broadly, JiT compilation includes any translation performed dynamically, after a program has started execution. We examine the motivation behind “just-in-time” compilation (JiT) techniques since the 1960s. Broadly, JiT compilation includes any translation performed dynamically, after a program has started execution. We examine the motivation behind

Recap: Translation Units • In C++, translation is performed in nine well-defined stages • Phases 1 through 6 perform lexical analysis (the pre-processor) • The output of Phase 6 is a translation unit unit • A translation unit is defined [5.1] as • A source file • Plus all the headers and source files included via #include directives • Minus any source lines skipped by conditional inclusion preprocessing template-id • A declaration introduces one or more names into a translation unit • A declaration may also re-introduce a name into a translation unit • A definition is a declaration that fully defines the

Top level ○ version, revision ○ sets ● Sets ○ family-name, name ○ visible-sets, translation-units ● Translation units ○ object, source, work-directory ○ arguments, baseline-arguments, local-arguments Scanning performance metrics 21Build Databases: Sets ● Each set has: ○ Name ○ Family name ○ Translation units ○ Visible sets (names of sets that provide modules that may be imported in this set) ● targets) ● Using “visible sets”, the target graph can be known by tooling 22Build Databases: Translation Units ● This is where existing compile database entries start showing up ○ Object (uniqueness

case study) The state of the ecosystem 4C++20 MODULES a short recap 5source.cpp library.h translation unit object file library.h library interface library.cpp library.h library implementation predefined, commandline defaults, commandline none translation unit files object file 6 . 2 discarded discarded some header.hsource.cpp translation unit object file export module library; library 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 10 . 5VISIBILITY hide and seek 11// translation unit 1 int i; // point of declaration (POD), introduces entity 'i' int j = i; // POD, introduces

mapping(extents_type parent_shape, extents_type shape, coordinate_t translation, double theta) {... 57 non-default constructorgithub.com/griswaldbrooks/spanny2 mapping(extents_type parent_shape, extents_type shape, coordinate_t translation, double theta) {... 58 non-default constructorgithub.com/griswaldbrooks/spanny2 layout_rotatable { struct mapping { private: extents_type shape_; coordinate_t translation_; double theta_; extents_type parent_shape_; size_type span_size_; }; }; 60

similarly to A New Main translation units go here -->