Misplaced Pages

#598401

39-828: LLVM is written in C++ and is designed for compile-time , link-time , runtime , and "idle-time" optimization. Originally implemented for C and C++, the language-agnostic design of LLVM has since spawned a wide variety of frontends: languages with compilers that use LLVM (or which do not directly use LLVM but can generate compiled programs as LLVM IR) include ActionScript , Ada , C# for .NET , Common Lisp , PicoLisp , Crystal , CUDA , D , Delphi , Dylan , Forth , Fortran , FreeBASIC , Free Pascal , Halide , Haskell , Idris , Java bytecode , Julia , Kotlin , LabVIEW 's G language, Lua , Objective-C , OpenCL , PostgreSQL 's SQL and PLpgSQL, Ruby , Rust , Scala , Standard ML , Swift , Xojo , and Zig . The LLVM project started in 2000 at

78-529: A polyhedral model . llvm-libc is an incomplete, upcoming, ABI independent C standard library designed by and for the LLVM project. Due to its permissive license, many vendors release their own tuned forks of LLVM. This is officially recognized by LLVM's documentation, which suggests against using version numbers in feature checks for this reason. Some of the vendors include: Compile-time In computer science , compile time (or compile-time ) describes

117-467: A concrete language can be represented by combining these basic types in LLVM. For example, a class in C++ can be represented by a mix of structures, functions and arrays of function pointers . The LLVM JIT compiler can optimize unneeded static branches out of a program at runtime, and thus is useful for partial evaluation in cases where a program has many options, most of which can easily be determined unneeded in

156-467: A practical machine language in three fundamental ways: A popular format for intermediate languages is three-address code . The term is also used to refer to languages used as intermediates by some high-level programming languages which do not output object or machine code themselves, but output the intermediate language only. This intermediate language is submitted to a compiler for such language, which then outputs finished object or machine code. This

195-466: A proper 3D hardware driver loaded. In 2011, programs compiled by GCC outperformed those from LLVM by 10%, on average. In 2013, phoronix reported that LLVM had caught up with GCC, compiling binaries of approximately equal performance. LLVM has become an umbrella project containing multiple components. LLVM was originally written to be a replacement for the extant code generator in the GCC stack, and many of

234-510: A specific environment. This feature is used in the OpenGL pipeline of Mac OS X Leopard (v10.5) to provide support for missing hardware features. Graphics code within the OpenGL stack can be left in intermediate representation and then compiled when run on the target machine. On systems with high-end graphics processing units (GPUs), the resulting code remains quite thin, passing the instructions on to

273-567: A target platform. LLVM can accept the IR from the GNU Compiler Collection (GCC) toolchain , allowing it to be used with a wide array of extant compiler front-ends written for that project. LLVM can also be built with gcc after version 7.5. LLVM can also generate relocatable machine code at compile-time or link-time or even binary machine code at runtime. LLVM supports a language-independent instruction set and type system . Each instruction

312-494: A team to work on the LLVM system for various uses within Apple's development systems. LLVM has been an integral part of Apple's Xcode development tools for macOS and iOS since Xcode 4 in 2011. In 2006, Lattner started working on a new project named Clang . The combination of Clang frontend and LLVM backend is named Clang/LLVM or simply Clang. The name LLVM was originally an initialism for Low Level Virtual Machine . However,

351-907: Is PNaCl . The LLVM project also introduces another type of intermediate representation named MLIR which helps build reusable and extensible compiler infrastructure by employing a plugin architecture named Dialect. It enables the use of higher-level information on the program structure in the process of optimization including polyhedral compilation . At version 16, LLVM supports many instruction sets , including IA-32 , x86-64 , ARM , Qualcomm Hexagon , LoongArch , M68K , MIPS , NVIDIA Parallel Thread Execution (PTX, also named NVPTX in LLVM documentation), PowerPC , AMD TeraScale , most recent AMD GPUs (also named AMDGPU in LLVM documentation), SPARC , z/Architecture (also named SystemZ in LLVM documentation), and XCore . Some features are not available on some platforms. Most features are present for IA-32, x86-64, z/Architecture, ARM, and PowerPC. RISC-V

390-407: Is LLVM's framework for translating machine instructions between textual forms and machine code. Formerly, LLVM relied on the system assembler, or one provided by a toolchain, to translate assembly into machine code. LLVM MC's integrated assembler supports most LLVM targets, including IA-32, x86-64, ARM, and ARM64. For some targets, including the various MIPS instruction sets, integrated assembly support

429-405: Is a stub . You can help Misplaced Pages by expanding it . Intermediate representation An intermediate representation ( IR ) is the data structure or code used internally by a compiler or virtual machine to represent source code . An IR is designed to be conducive to further processing, such as optimization and translation . A "good" IR must be accurate – capable of representing

SECTION 10

#1733094462599

468-524: Is aimed at replacing the C/Objective-C compiler in the GCC system with a system that is more easily integrated with integrated development environments (IDEs) and has wider support for multithreading . Support for OpenMP directives has been included in Clang since release 3.8. The Utrecht Haskell compiler can generate code for LLVM. While the generator was in early stages of development, in many cases it

507-594: Is in static single assignment form (SSA), meaning that each variable (called a typed register) is assigned once and then frozen. This helps simplify the analysis of dependencies among variables. LLVM allows code to be compiled statically, as it is under the traditional GCC system, or left for late-compiling from the IR to machine code via just-in-time compilation (JIT), similar to Java . The type system consists of basic types such as integer or floating-point numbers and five derived types : pointers , arrays , vectors , structures , and functions . A type construct in

546-431: Is mostly obsolete. LLVM currently supports compiling of Ada , C , C++ , D , Delphi , Fortran , Haskell , Julia , Objective-C , Rust , and Swift using various frontends . Widespread interest in LLVM has led to several efforts to develop new frontends for many languages. The one that has received the most attention is Clang, a newer compiler supporting C, C++, and Objective-C. Primarily supported by Apple, Clang

585-810: Is supported as of version 7. In the past, LLVM also supported other backends, fully or partially, including C backend, Cell SPU , mblaze (MicroBlaze) , AMD R600, DEC/Compaq Alpha ( Alpha AXP ) and Nios2 , but that hardware is mostly obsolete, and LLVM developers decided the support and maintenance costs were no longer justified. LLVM also supports WebAssembly as a target, enabling compiled programs to execute in WebAssembly-enabled environments such as Google Chrome / Chromium , Firefox , Microsoft Edge , Apple Safari or WAVM . LLVM-compliant WebAssembly compilers typically support mostly unmodified source code written in C, C++, D, Rust, Nim, Kotlin and several other languages. The LLVM machine code (MC) subproject

624-401: Is the language of an abstract machine designed to aid in the analysis of computer programs . The term comes from their use in compilers , where the source code of a program is translated into a form more suitable for code-improving transformations before being used to generate object or machine code for a target machine. The design of an intermediate language typically differs from that of

663-540: Is usable but still in the beta stage. The lld subproject is an attempt to develop a built-in, platform-independent linker for LLVM. lld aims to remove dependence on a third-party linker. As of May 2017, lld supports ELF , PE/COFF , Mach-O , and WebAssembly in descending order of completeness. lld is faster than both flavors of GNU ld . Unlike the GNU linkers, lld has built-in support for link-time optimization (LTO). This allows for faster code generation as it bypasses

702-451: Is usually done to ease the process of optimization or to increase portability by using an intermediate language that has compilers for many processors and operating systems , such as C . Languages used for this fall in complexity between high-level languages and low-level languages, such as assembly languages . Though not explicitly designed as an intermediate language, C 's nature as an abstraction of assembly and its ubiquity as

741-399: The C Intermediate Language . Any language targeting a virtual machine or p-code machine can be considered an intermediate language: The GNU Compiler Collection (GCC) uses several intermediate languages internally to simplify portability and cross-compilation . Among these languages are GCC supports generating these IRs, as a final target: The LLVM compiler framework is based on

780-496: The LLVM IR intermediate language, of which the compact, binary serialized representation is also referred to as "bitcode" and has been productized by Apple. Like GIMPLE Bytecode, LLVM Bitcode is useful in link-time optimization. Like GCC, LLVM also targets some IRs meant for direct distribution, including Google's PNaCl IR and SPIR . A further development within LLVM is the use of Multi-Level Intermediate Representation ( MLIR ) with

819-552: The Rust compiler, a Java bytecode frontend, a Common Intermediate Language (CIL) frontend, the MacRuby implementation of Ruby 1.9, various frontends for Standard ML , and a new graph coloring register allocator. The core of LLVM is the intermediate representation (IR), a low-level programming language similar to assembly. IR is a strongly typed reduced instruction set computer (RISC) instruction set which abstracts away most details of

SECTION 20

#1733094462599

858-478: The University of Illinois at Urbana–Champaign , under the direction of Vikram Adve and Chris Lattner . LLVM was originally developed as a research infrastructure to investigate dynamic compilation techniques for static and dynamic programming languages. LLVM was released under the University of Illinois/NCSA Open Source License , a permissive free software licence . In 2005, Apple Inc. hired Lattner and formed

897-499: The de facto system language in Unix-like and other operating systems has made it a popular intermediate language: Eiffel , Sather , Esterel , some dialects of Lisp ( Lush , Gambit ), Squeak 's Smalltalk-subset Slang, Nim , Cython , Seed7 , SystemTap , Vala , V, and others make use of C as an intermediate language. Variants of C have been designed to provide C's features as a portable assembly language , including C-- and

936-508: The GCC frontends have been modified to work with it, resulting in the now-defunct LLVM-GCC suite. The modifications generally involve a GIMPLE -to-LLVM IR step so that LLVM optimizers and codegen can be used instead of GCC's GIMPLE system. Apple was a significant user of LLVM-GCC through Xcode 4.x (2013). This use of the GCC frontend was considered mostly a temporary measure, but with the advent of Clang and advantages of LLVM and Clang's modern and modular codebase (as well as compilation speed),

975-570: The GPU with minimal changes. On systems with low-end GPUs, LLVM will compile optional procedures that run on the local central processing unit (CPU) that emulate instructions that the GPU cannot run internally. LLVM improved performance on low-end machines using Intel GMA chipsets. A similar system was developed under the Gallium3D LLVMpipe, and incorporated into the GNOME shell to allow it to run without

1014-617: The LLVM implementation of the C++ Standard Library (with full support of C++11 and C++14 ), etc. LLVM is administered by the LLVM Foundation. Compiler engineer Tanya Lattner became its president in 2014 and was in post as of March 2024. "For designing and implementing LLVM" , the Association for Computing Machinery presented Vikram Adve, Chris Lattner, and Evan Cheng with the 2012 ACM Software System Award . The project

1053-404: The LLVM project evolved into an umbrella project that has little relationship to what most current developers think of as a virtual machine . This made the initialism "confusing" and "inappropriate", and since 2011 LLVM is "officially no longer an acronym", but a brand that applies to the LLVM umbrella project. The project encompasses the LLVM intermediate representation (IR), the LLVM debugger ,

1092-426: The amount of storage required by types and variables can be deduced. Properties of a program that can be reasoned about at compile time include range-checks (e.g., proving that an array index will not exceed the array bounds), deadlock freedom in concurrent languages , or timings (e.g., proving that a sequence of code takes no more than an allocated amount of time). Compile-time occurs before link time (when

1131-594: The following compiler phases (which therefore occur at compile-time): syntax analysis , semantic analysis , and code generation . During optimization phases, constant expressions in the source code can also be evaluated at compile-time using compile-time execution , which reduces the constant expressions to a single value. This is not necessary for correctness, but improves program performance during runtime. Programming language definitions usually specify compile time requirements that source code must meet to be successfully compiled. For example, languages may stipulate that

1170-467: The human-readable IR format: The many different conventions used and features provided by different targets mean that LLVM cannot truly produce a target-independent IR and retarget it without breaking some established rules. Examples of target dependence beyond what is explicitly mentioned in the documentation can be found in a 2011 proposal for "wordcode", a fully target-independent variant of LLVM IR intended for online distribution. A more practical example

1209-414: The linear human-readable text representing a program into an intermediate graph structure that allows flow analysis and re-arrangement before execution. Use of an intermediate representation such as this allows compiler systems like the GNU Compiler Collection and LLVM to be used by many different source languages to generate code for many different target architectures . An intermediate language

LLVM - Misplaced Pages Continue

1248-414: The output of one or more compiled files are joined) and runtime (when a program is executed ). Although in the case of dynamic compilation , the final transformations into machine language happen at runtime. There is a trade-off between compile-time and link-time in that many compile time operations can be deferred to link-time without incurring run-time cost. This computer science article

1287-402: The program that can be reasoned about during compilation. The actual length of time it takes to compile a program is usually referred to as compilation time . The determination of execution model have been set during the compile time stage. Run time- the method of execution and allocation - have been set during the run time and are based on the run time dynamicity. Most compilers have at least

1326-471: The source code without loss of information – and independent of any particular source or target language. An IR may take one of several forms: an in-memory data structure , or a special tuple - or stack -based code readable by the program. In the latter case it is also called an intermediate language . A canonical example is found in most modern compilers. For example, the CPython interpreter transforms

1365-439: The target. For example, the calling convention is abstracted through call and ret instructions with explicit arguments. Also, instead of a fixed set of registers, IR uses an infinite set of temporaries of the form %0, %1, etc. LLVM supports three equivalent forms of IR: a human-readable assembly format, an in-memory format suitable for frontends, and a dense bitcode format for serializing. A simple "Hello, world!" program in

1404-487: The time window during which a language's statements are converted into binary instructions for the processor to execute. The term is used as an adjective to describe concepts related to the context of program compilation, as opposed to concepts related to the context of program execution ( runtime ). For example, compile-time requirements are programming language requirements that must be met by source code before compilation and compile-time properties are properties of

1443-606: The use of a linker plugin, but on the other hand prohibits interoperability with other flavors of LTO. The LLVM project includes an implementation of the C++ Standard Library named libc++, dual-licensed under the MIT License and the UIUC license . Since v9.0.0, it was relicensed to the Apache License 2.0 with LLVM Exceptions. This implements a suite of cache-locality optimizations as well as auto-parallelism and vectorization using

1482-445: Was more efficient than the C code generator. The Glasgow Haskell Compiler (GHC) backend uses LLVM and achieves a 30% speed-up of compiled code relative to native code compiling via GHC or C code generation followed by compiling, missing only one of the many optimizing techniques implemented by the GHC. Many other components are in various stages of development, including, but not limited to,

1521-481: Was originally available under the UIUC license . After v9.0.0 released in 2019, LLVM relicensed to the Apache License 2.0 with LLVM Exceptions. As of November 2022 about 400 contributions had not been relicensed. LLVM can provide the middle layers of a complete compiler system, taking intermediate representation (IR) code from a compiler and emitting an optimized IR. This new IR can then be converted and linked into machine-dependent assembly language code for

#598401