| commit | e3e25b51122573c12c30f25b1b3a1b556fca237b | [log] [tgz] |
|---|---|---|
| author | Arthur Eubanks <aeubanks@google.com> | Tue Nov 16 12:58:13 2021 -0800 |
| committer | Arthur Eubanks <aeubanks@google.com> | Wed Nov 17 09:06:46 2021 -0800 |
| tree | e0b420c7b7a32b8b8dab7de27a600bbb1783e0ed | |
| parent | 2e7f12d5e9f998dcce62dd4a2e93a7a10dfc2515 [diff] |
[NewPM] Add option to prevent rerunning function pipeline on functions in CGSCC adaptor In a CGSCC pass manager, we may visit the same function multiple times due to SCC mutations. In the inliner pipeline, this results in running the function simplification pipeline on a function multiple times even if it hasn't been changed since the last function simplification pipeline run. We use a newly introduced analysis to keep track of whether or not a function has changed since the last time the function simplification pipeline has run on it. If we see this analysis available for a function in a CGSCCToFunctionPassAdaptor, we skip running the function passes on the function. The analysis is queried at the end of the function passes so that it's available after the first time the function simplification pipeline runs on a function. This is a per-adaptor option so it doesn't apply to every adaptor. The goal of this is to improve compile times. However, currently we can't turn this on by default at least for the higher optimization levels since the function simplification pipeline is not robust enough to be idempotent in many cases, resulting in performance regressions if we stop running the function simplification pipeline on a function multiple times. We may be able to turn this on for -O1 in the near future, but turning this on for higher optimization levels would require more investment in the function simplification pipeline. Heavily inspired by D98103. Example compile time improvements with flag turned on: https://llvm-compile-time-tracker.com/compare.php?from=998dc4a5d3491d2ae8cbe742d2e13bc1b0cacc5f&to=5c27c913687d3d5559ef3ab42b5a3d513531d61c&stat=instructions Reviewed By: asbirlea, nikic Differential Revision: https://reviews.llvm.org/D113947
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.
Taken from https://llvm.org/docs/GettingStarted.html.
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 convert them 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.
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:
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
Configure and build LLVM and Clang:
cd llvm-project
cmake -S llvm -B build -G <generator> [options]
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, compiler-rt,cross-project-tests, flang, libc, libclc, libcxx, libcxxabi, libunwind, lld, lldb, mlir, openmp, polly, or pstl.
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 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.