1 / 22

lld

lld. The LLVM Linker. What is lld?. A system linker Produce final libraries and executables , no other tools or runtime required Understands platform ABI. What is lld?. A system linker Modular and embeddable Designed as a set of libraries

ptiggs
Download Presentation

lld

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. 2012 LLVM Euro - Michael Spencer lld The LLVM Linker

  2. What is lld? • A system linker • Produce final libraries and executables, no other tools or runtime required • Understands platform ABI 2012 LLVM Euro - Michael Spencer

  3. What is lld? • A system linker • Modular and embeddable • Designed as a set of libraries • As with all LLVM/Clang tools, the main executable code is quite short. • Can be embedded into other tools such as custom language compilers. 2012 LLVM Euro - Michael Spencer

  4. What is lld? • A system linker • Modular and embeddable • Portable (both host and target) • Currently tested on Mac, Linux, and Windows • Target specific code is isolated for both OS and CPU architecture 2012 LLVM Euro - Michael Spencer

  5. What is lld? • A system linker • Modular and embeddable • Portable (both host and target) • Compatible • Driver to support multiple styles (gnu-ld, ld64, link.exe) • Supports ELF, COFF (including MinGW), Mach-O, and LLVM IR • Support for a restricted subset of linker scripts is planned 2012 LLVM Euro - Michael Spencer

  6. What is lld? • A system linker • Modular and embeddable • Portable (both host and target) • Compatible • Extensible • Both LLVM IR and atom graph passes can be added 2012 LLVM Euro - Michael Spencer

  7. Why a new linker? • Performance • Linking is a speed bump in the way of fast iteration • gold may be fast, but gnu-ld and link.exe are not, and gold is ELF only 2012 LLVM Euro - Michael Spencer

  8. Why a new linker? • Performance • Portability • gold and gnu-ld are UNIX-oriented, link.exe is Windows only, and ld64 is Darwin only. 2012 LLVM Euro - Michael Spencer

  9. Why a new linker? • Performance • Portability • Reliable cross linking • No single linker can currently be used to reliably cross link 2012 LLVM Euro - Michael Spencer

  10. What makes lld different? • Atom Model • An atom is an indivisible chunk of code or data • It has a set of attributes such as type, name, and scope • It has a list of references to other atoms • References represent relocations and other relationships such as grouping. 2012 LLVM Euro - Michael Spencer

  11. Atom Model • An atom is an indivisible chunk of code or data An atom 2012 LLVM Euro - Michael Spencer

  12. Atom Model • It has a set of attributes such as type, name, and scope name: main type: code scope: global But not all atoms have names • type: data • scope: static • content: "Hello, World!" 2012 LLVM Euro - Michael Spencer

  13. Atom Model • It has a list of references to other atoms name: main type: code scope: global • name: printf • def: undefined • type: data • scope: static • content: "Hello, World!" 2012 LLVM Euro - Michael Spencer

  14. Atom Model • References represent relocations and other relationships such as grouping. name: main type: code scope: global offset: 24 type: R_X86_64_PC32 addend: -4 offset: 12 type: R_X86_64_32S • name: printf • def: undefined • type: data • scope: static • content: "Hello, World!" 2012 LLVM Euro - Michael Spencer

  15. What makes lld different? • Atom Model • LLVM IR and atom graph passes • In addition to the standard LLVM passes, other passes can run at pre and post LLVM IR link phases • lld passes can be run over the atom graph at different stages of the link • Branch island generation • Order file • C++ Open Multi-Methods… 2012 LLVM Euro - Michael Spencer

  16. What makes lld different? • Atom Model • LLVM IR and atom graph passes • Uniform text, binary, and in memory representation • lld supports a human-readable YAML input and output format to aid in testing and debugging 2012 LLVM Euro - Michael Spencer

  17. Uniform Representation # RUN: lld-core %s 2>&1 | FileCheck %s # CHECK: duplicate symbol --- atoms: - name: _foo scope: global type: data --- atoms: - name: _foo scope: global type: code ... 2012 LLVM Euro - Michael Spencer

  18. What makes lld different? • Atom Model • LLVM IR and atom graph passes • Uniform text, binary, and in memory representation • lld supports a human readable YAML input and output format to aid in testing and debugging • lld also adds a binary representation of the in memory atom model • The purpose of this is purely for speed • The goal is for LLVM to eventually produce these natively 2012 LLVM Euro - Michael Spencer

  19. What makes lld different? • Atom Model • LLVM IR and atom graph passes • Uniform text, binary, and in memory representation • C++11 • lld has been developed using C++11 from the beginning • Dogfooding Clang and libc++ • Makes it easier to write faster code • C++11 atomics and memory model for multithreading 2012 LLVM Euro - Michael Spencer

  20. Project Status • Atom graph and resolving work with YAML as input and output • lld native binary reading and writing • COFF and Mach-O are already in progress • The Mach-O writer can produce a Hello World executable from multiple YAML files 2012 LLVM Euro - Michael Spencer

  21. Patches Welcome • Open Projects • http://lld.llvm.org/open_projects.html 2012 LLVM Euro - Michael Spencer

  22. 2012 LLVM Euro - Michael Spencer Questions? bigcheesegs@gmail.com

More Related