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A GNU Manual
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You have freedom to copy and modify this GNU Manual, like GNU software. Copies published by the Free Software Foundation raise funds for GNU development.
Short ContentsIntroduction 1 Contributing to GCC Development 2 GCC and Portability 3 Interfacing to GCC Output 4 The GCC low-level runtime library 5 Language Front Ends in GCC 6 Source Tree Structure and Build System 7 Option specification files 8 Passes and Files of the Compiler 9 Trees: The intermediate representation used by the C and C++ front ends 10 Analysis and Optimization of GIMPLE Trees 11 RTL Representation 12 Control Flow Graph 13 Machine Descriptions 14 Target Description Macros and Functions 15 Host Configuration 16 Makefile Fragments 17 collect2 18 Standard Header File Directories 19 Memory Management and Type Information Funding Free Software The GNU Project and GNU/Linux GNU GENERAL PUBLIC LICENSE GNU Free Documentation License Contributors to GCC Option Index Concept Index
Table of ContentsIntroduction 1 Contributing to GCC Development 2 GCC and Portability 3 Interfacing to GCC Output 4 The GCC low-level runtime library 4.1 Routines for integer arithmetic 4.1.1 Arithmetic functions 4.1.2 Comparison functions 4.1.3 Trapping arithmetic functions 4.1.4 Bit operations 4.2 Routines for floating point emulation 4.2.1 Arithmetic functions 4.2.2 Conversion functions 4.2.3 Comparison functions 4.3 Language-independent routines for exception handling 4.4 Miscellaneous runtime library routines 4.4.1 Cache control functions 5 Language Front Ends in GCC 6 Source Tree Structure and Build System 6.1 Configure Terms and History 6.2 Top Level Source Directory 6.3 The gcc Subdirectory 6.3.1 Subdirectories of gcc 6.3.2 Configuration in the gcc Directory 6.3.2.1 Scripts Used by configure 6.3.2.2 The config.build; config.host; and config.gcc Files 6.3.2.3 Files Created by configure 6.3.3 Build System in the gcc Directory 6.3.4 Makefile Targets 6.3.5 Library Source Files and Headers under the gcc Directory 6.3.6 Headers Installed by GCC 6.3.7 Building Documentation 6.3.7.1 Texinfo Manuals 6.3.7.2 Man Page Generation 6.3.7.3 Miscellaneous Documentation 6.3.8 Anatomy of a Language Front End 6.3.8.1 The Front End language Directory 6.3.8.2 The Front End config-lang.in File 6.3.9 Anatomy of a Target Back End 6.4 Testsuites 6.4.1 Idioms Used in Testsuite Code 6.4.2 Directives used within DejaGnu tests 6.4.3 Ada Language Testsuites 6.4.4 C Language Testsuites 6.4.5 The Java library testsuites. 6.4.6 Support for testing gcov 6.4.7 Support for testing profile-directed optimizations 6.4.8 Support for testing binary compatibility 7 Option specification files 7.1 Option file format 7.2 Option properties 8 Passes and Files of the Compiler 8.1 Parsing pass 8.2 Gimplification pass 8.3 Pass manager 8.4 Tree-SSA passes 8.5 RTL passes 9 Trees: The intermediate representation used by the C and C++ front ends 9.1 Deficiencies 9.2 Overview 9.2.1 Trees 9.2.2 Identifiers 9.2.3 Containers 9.3 Types 9.4 Scopes 9.4.1 Namespaces 9.4.2 Classes 9.5 Declarations 9.6 Functions 9.6.1 Function Basics 9.6.2 Function Bodies 9.6.2.1 Statements 9.7 Attributes in trees 9.8 Expressions 10 Analysis and Optimization of GIMPLE Trees 10.1 GENERIC 10.2 GIMPLE 10.2.1 Interfaces 10.2.2 Temporaries 10.2.3 Expressions 10.2.3.1 Compound Expressions 10.2.3.2 Compound Lvalues 10.2.3.3 Conditional Expressions 10.2.3.4 Logical Operators 10.2.4 Statements 10.2.4.1 Blocks 10.2.4.2 Statement Sequences 10.2.4.3 Empty Statements 10.2.4.4 Loops 10.2.4.5 Selection Statements 10.2.4.6 Jumps 10.2.4.7 Cleanups 10.2.4.8 Exception Handling 10.2.5 GIMPLE Example 10.2.6 Rough GIMPLE Grammar 10.3 Annotations 10.4 Statement Operands 10.4.1 Operand Iterators And Access Routines 10.4.2 Immediate Uses 10.5 Static Single Assignment 10.5.1 Preserving the SSA form 10.5.2 Examining SSA_NAME nodes 10.5.3 Walking use-def chains 10.5.4 Walking the dominator tree 10.6 Alias analysis 11 RTL Representation 11.1 RTL Object Types 11.2 RTL Classes and Formats 11.3 Access to Operands 11.4 Access to Special Operands 11.5 Flags in an RTL Expression 11.6 Machine Modes 11.7 Constant Expression Types 11.8 Registers and Memory 11.9 RTL Expressions for Arithmetic 11.10 Comparison Operations 11.11 Bit-Fields 11.12 Vector Operations 11.13 Conversions 11.14 Declarations 11.15 Side Effect Expressions 11.16 Embedded Side-Effects on Addresses 11.17 Assembler Instructions as Expressions 11.18 Insns 11.19 RTL Representation of Function-Call Insns 11.20 Structure Sharing Assumptions 11.21 Reading RTL 12 Control Flow Graph 12.1 Basic Blocks 12.2 Edges 12.3 Profile information 12.4 Maintaining the CFG 12.5 Liveness information 13 Machine Descriptions 13.1 Overview of How the Machine Description is Used 13.2 Everything about Instruction Patterns 13.3 Example of define_insn 13.4 RTL Template 13.5 Output Templates and Operand Substitution 13.6 C Statements for Assembler Output 13.7 Predicates 13.7.1 Machine-Independent Predicates 13.7.2 Defining Machine-Specific Predicates 13.8 Operand Constraints 13.8.1 Simple Constraints 13.8.2 Multiple Alternative Constraints 13.8.3 Register Class Preferences 13.8.4 Constraint Modifier Characters 13.8.5 Constraints for Particular Machines 13.9 Standard Pattern Names For Generation 13.10 When the Order of Patterns Matters 13.11 Interdependence of Patterns 13.12 Defining Jump Instruction Patterns 13.13 Defining Looping Instruction Patterns 13.14 Canonicalization of Instructions 13.15 Defining RTL Sequences for Code Generation 13.16 Defining How to Split Instructions 13.17 Including Patterns in Machine Descriptions. 13.17.1 RTL Generation Tool Options for Directory Search 13.18 Machine-Specific Peephole Optimizers 13.18.1 RTL to Text Peephole Optimizers 13.18.2 RTL to RTL Peephole Optimizers 13.19 Instruction Attributes 13.19.1 Defining Attributes and their Values 13.19.2 Attribute Expressions 13.19.3 Assigning Attribute Values to Insns 13.19.4 Example of Attribute Specifications 13.19.5 Computing the Length of an Insn 13.19.6 Constant Attributes 13.19.7 Delay Slot Scheduling 13.19.8 Specifying processor pipeline description 13.20 Conditional Execution 13.21 Constant Definitions 13.22 Macros 13.22.1 Mode Macros 13.22.1.1 Defining Mode Macros 13.22.1.2 Substitution in Mode Macros 13.22.1.3 Mode Macro Examples 13.22.2 Code Macros 14 Target Description Macros and Functions 14.1 The Global targetm Variable 14.2 Controlling the Compilation Driver, gcc 14.3 Run-time Target Specification 14.4 Defining data structures for per-function information. 14.5 Storage Layout 14.6 Layout of Source Language Data Types 14.7 Register Usage 14.7.1 Basic Characteristics of Registers 14.7.2 Order of Allocation of Registers 14.7.3 How Values Fit in Registers 14.7.4 Handling Leaf Functions 14.7.5 Registers That Form a Stack 14.8 Register Classes 14.9 Stack Layout and Calling Conventions 14.9.1 Basic Stack Layout 14.9.2 Exception Handling Support 14.9.3 Specifying How Stack Checking is Done 14.9.4 Registers That Address the Stack Frame 14.9.5 Eliminating Frame Pointer and Arg Pointer 14.9.6 Passing Function Arguments on the Stack 14.9.7 Passing Arguments in Registers 14.9.8 How Scalar Function Values Are Returned 14.9.9 How Large Values Are Returned 14.9.10 Caller-Saves Register Allocation 14.9.11 Function Entry and Exit 14.9.12 Generating Code for Profiling 14.9.13 Permitting tail calls 14.10 Implementing the Varargs Macros 14.11 Trampolines for Nested Functions 14.12 Implicit Calls to Library Routines 14.13 Addressing Modes 14.14 Condition Code Status 14.15 Describing Relative Costs of Operations 14.16 Adjusting the Instruction Scheduler 14.17 Dividing the Output into Sections (Texts, Data, ...) 14.18 Position Independent Code 14.19 Defining the Output Assembler Language 14.19.1 The Overall Framework of an Assembler File 14.19.2 Output of Data 14.19.3 Output of Uninitialized Variables 14.19.4 Output and Generation of Labels 14.19.5 How Initialization Functions Are Handled 14.19.6 Macros Controlling Initialization Routines 14.19.7 Output of Assembler Instructions 14.19.8 Output of Dispatch Tables 14.19.9 Assembler Commands for Exception Regions 14.19.10 Assembler Commands for Alignment 14.20 Controlling Debugging Information Format 14.20.1 Macros Affecting All Debugging Formats 14.20.2 Specific Options for DBX Output 14.20.3 Open-Ended Hooks for DBX Format 14.20.4 File Names in DBX Format 14.20.5 Macros for SDB and DWARF Output 14.20.6 Macros for VMS Debug Format 14.21 Cross Compilation and Floating Point 14.22 Mode Switching Instructions 14.23 Defining target-specific uses of __attribute__ 14.24 Defining coprocessor specifics for MIPS targets. 14.25 Parameters for Precompiled Header Validity Checking 14.26 C++ ABI parameters 14.27 Miscellaneous Parameters 15 Host Configuration 15.1 Host Common 15.2 Host Filesystem 15.3 Host Misc 16 Makefile Fragments 16.1 Target Makefile Fragments 16.2 Host Makefile Fragments 17 collect2 18 Standard Header File Directories 19 Memory Management and Type Information 19.1 The Inside of a GTY(()) 19.2 Marking Roots for the Garbage Collector 19.3 Source Files Containing Type Information Funding Free Software The GNU Project and GNU/Linux GNU GENERAL PUBLIC LICENSE Preamble How to Apply These Terms to Your New Programs GNU Free Documentation License ADDENDUM: How to use this License for your documents Contributors to GCC Option Index Concept Index
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IntroductionThis manual documents the internals of the GNU compilers, including how to port them to new targets and some information about how to write front ends for new languages. It corresponds to GCC version 4.1.0. The use of the GNU compilers is documented in a separate manual. See Introduction.
This manual is mainly a reference manual rather than a tutorial. It discusses how to contribute to GCC (see Contributing), the characteristics of the machines supported by GCC as hosts and targets (see Portability), how GCC relates to the ABIs on such systems (see Interface), and the characteristics of the languages for which GCC front ends are written (see Languages). It then describes the GCC source tree structure and build system, some of the interfaces to GCC front ends, and how support for a target system is implemented in GCC.
Additional tutorial information is linked to from http://gcc.gnu.org/readings.html.
Contributing: How to contribute to testing and developing GCC. Portability: Goals of GCC's portability features. Interface: Function-call interface of GCC output. Libgcc: Low-level runtime library used by GCC. Languages: Languages for which GCC front ends are written. Source Tree: GCC source tree structure and build system. Options: Option specification files. Passes: Order of passes, what they do, and what each file is for. Trees: The source representation used by the C and C++ front ends. RTL: The intermediate representation that most passes work on. Control Flow: Maintaining and manipulating the control flow graph. Tree SSA: Analysis and optimization of the tree representation. Machine Desc: How to write machine description instruction patterns. Target Macros: How to write the machine description C macros and functions. Host Config: Writing the xm-machine.h file. Fragments: Writing the t-target and x-host files. Collect2: How collect2 works; how it finds ld. Header Dirs: Understanding the standard header file directories. Type Information: GCC's memory management; generating type information. Funding: How to help assure funding for free software. GNU Project: The GNU Project and GNU/Linux. Copying: GNU General Public License says how you can copy and share GCC. GNU Free Documentation License: How you can copy and share this manual. Contributors: People who have contributed to GCC. Option Index: Index to command line options. Concept Index: Index of concepts and symbol names.
