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gerrit-public.fairphone.software / toolchain / llvm-project / ad1b9daa4bf40c1907794fd5de7807aad1f0553c
commitad1b9daa4bf40c1907794fd5de7807aad1f0553c[log] [tgz]
authorSriraman Tallam <tmsriram@google.com>Mon Oct 26 14:20:35 2020 -0700
committerSriraman Tallam <tmsriram@google.com>Mon Oct 26 14:24:28 2020 -0700
treee1069e288ca5b5abaa9414e824080f96113040cb
parentdf6d2e8ab1a4212284e4763724a2211df2c7394a [diff]
Prepend "__uniq" to symbol names hash with -funique-internal-linkage-names.

Prepend the module name hash with a fixed string ".__uniq." which helps tools
that consume sampled profiles and attribute it to functions to understand
that this symbol belongs to a unique internal linkage type symbol.

Symbols with suffixes can result from various optimizations in the compiler.
Function Multiversioning, function splitting, parameter constant propogation,
unique internal linkage names.

External tools like sampled profile aggregators combine profiles from multiple
runs of a binary. They use various heuristics with symbols that have suffixes
to try and attribute the profile to the right function instance. For instance
multi-versioned symbols like foo.avx, foo.sse4.2, etc even though different
should be attributed to the same source function if a single function is
versioned, using attribute target_clones (supported in GCC but yet to land in
LLVM). Similarly, functions that are split (split part having a .cold suffix)
could have profiles for both the original and split symbols but would be
aggregated and attributed to the original function that was split.

Unique internal linkage functions however have different source instances and
the aggregator must not put them together but attribute it to the appropriate
function instance. To be sure that we are dealing with a symbol of a unique
internal linkage function, we would like to prepend the hash with a known
string ".__uniq." which these tools can check to understand the suffix type.

Differential Revision: https://reviews.llvm.org/D89617
3 files changed
tree: e1069e288ca5b5abaa9414e824080f96113040cb
  1. clang/
  2. clang-tools-extra/
  3. compiler-rt/
  4. debuginfo-tests/
  5. flang/
  6. libc/
  7. libclc/
  8. libcxx/
  9. libcxxabi/
  10. libunwind/
  11. lld/
  12. lldb/
  13. llvm/
  14. mlir/
  15. openmp/
  16. parallel-libs/
  17. polly/
  18. pstl/
  19. utils/
  20. .arcconfig
  21. .arclint
  22. .clang-format
  23. .clang-tidy
  24. .git-blame-ignore-revs
  25. .gitignore
  26. CONTRIBUTING.md
  27. README.md
README.md

The LLVM Compiler Infrastructure

This directory and its sub-directories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and run-time environments.

The README briefly describes how to get started with building LLVM. For more information on how to contribute to the LLVM project, please take a look at the Contributing to LLVM guide.

Getting Started with the LLVM System

Taken from https://llvm.org/docs/GettingStarted.html.

Overview

Welcome to the LLVM project!

The LLVM project has multiple components. The core of the project is itself called "LLVM". This contains all of the tools, libraries, and header files needed to process intermediate representations and converts it into object files. Tools include an assembler, disassembler, bitcode analyzer, and bitcode optimizer. It also contains basic regression tests.

C-like languages use the Clang front end. This component compiles C, C++, Objective-C, and Objective-C++ code into LLVM bitcode -- and from there into object files, using LLVM.

Other components include: the libc++ C++ standard library, the LLD linker, and more.

Getting the Source Code and Building LLVM

The LLVM Getting Started documentation may be out of date. The Clang Getting Started page might have more accurate information.

This is an example work-flow and configuration to get and build the LLVM source:

  1. Checkout LLVM (including related sub-projects like Clang):

    • git clone https://github.com/llvm/llvm-project.git

    • Or, on windows, git clone --config core.autocrlf=false https://github.com/llvm/llvm-project.git

  2. Configure and build LLVM and Clang:

    • cd llvm-project

    • mkdir build

    • cd build

    • cmake -G <generator> [options] ../llvm

      Some common build system generators are:

      • Ninja --- for generating Ninja build files. Most llvm developers use Ninja.
      • Unix Makefiles --- for generating make-compatible parallel makefiles.
      • Visual Studio --- for generating Visual Studio projects and solutions.
      • Xcode --- for generating Xcode projects.

      Some Common options:

      • -DLLVM_ENABLE_PROJECTS='...' --- semicolon-separated list of the LLVM sub-projects you'd like to additionally build. Can include any of: clang, clang-tools-extra, libcxx, libcxxabi, libunwind, lldb, compiler-rt, lld, polly, or debuginfo-tests.

        For example, to build LLVM, Clang, libcxx, and libcxxabi, use -DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi".

      • -DCMAKE_INSTALL_PREFIX=directory --- Specify for directory the full path name of where you want the LLVM tools and libraries to be installed (default /usr/local).

      • -DCMAKE_BUILD_TYPE=type --- Valid options for type are Debug, Release, RelWithDebInfo, and MinSizeRel. Default is Debug.

      • -DLLVM_ENABLE_ASSERTIONS=On --- Compile with assertion checks enabled (default is Yes for Debug builds, No for all other build types).

    • cmake --build . [-- [options] <target>] or your build system specified above directly.

      • The default target (i.e. ninja or make) will build all of LLVM.

      • The check-all target (i.e. ninja check-all) will run the regression tests to ensure everything is in working order.

      • CMake will generate targets for each tool and library, and most LLVM sub-projects generate their own check-<project> target.

      • Running a serial build will be slow. To improve speed, try running a parallel build. That's done by default in Ninja; for make, use the option -j NNN, where NNN is the number of parallel jobs, e.g. the number of CPUs you have.

    • For more information see CMake

Consult the Getting Started with LLVM page for detailed information on configuring and compiling LLVM. You can visit Directory Layout to learn about the layout of the source code tree.