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llvm / llvm-project / ce97ce3a5d72163fa217f367b1f8c8cab84c5963
commitce97ce3a5d72163fa217f367b1f8c8cab84c5963[log] [tgz]
authorSanjay Patel <spatel@rotateright.com>Fri Apr 03 13:53:54 2020 -0400
committerSanjay Patel <spatel@rotateright.com>Fri Apr 03 13:55:13 2020 -0400
tree3c33c6fd3ab11860ba880f6f7d4150addb770738
parente4ae0a2e975137a2596df06158317fcb2d21b86d [diff]
[VectorCombine] try to form a better extractelement

Extracting to the same index that we are going to insert back into
allows forming select ("blend") shuffles and enables further transforms.

Admittedly, this is a quick-fix for a more general problem that I'm
hoping to solve by adding transforms for patterns that start with an
insertelement.

But this might resolve some regressions known to be caused by the
extract-extract transform (although I have not gotten more details on
those yet).

In the motivating case from PR34724:
https://bugs.llvm.org/show_bug.cgi?id=34724

The combination of subsequent instcombine and codegen transforms gets us this improvement:

  vmovshdup	%xmm0, %xmm2    ## xmm2 = xmm0[1,1,3,3]
  vhaddps	%xmm1, %xmm1, %xmm4
  vmovshdup	%xmm1, %xmm3    ## xmm3 = xmm1[1,1,3,3]
  vaddps	%xmm0, %xmm2, %xmm0
  vaddps	%xmm1, %xmm3, %xmm1
  vshufps	$200, %xmm4, %xmm0, %xmm0 ## xmm0 = xmm0[0,2],xmm4[0,3]
  vinsertps	$177, %xmm1, %xmm0, %xmm0 ## xmm0 = zero,xmm0[1,2],xmm1[2]

  -->

  vmovshdup	%xmm0, %xmm2    ## xmm2 = xmm0[1,1,3,3]
  vhaddps	%xmm1, %xmm1, %xmm1
  vaddps	%xmm0, %xmm2, %xmm0
  vshufps	$200, %xmm1, %xmm0, %xmm0 ## xmm0 = xmm0[0,2],xmm1[0,3]

Differential Revision: https://reviews.llvm.org/D76623
3 files changed
tree: 3c33c6fd3ab11860ba880f6f7d4150addb770738
  1. clang/
  2. clang-tools-extra/
  3. compiler-rt/
  4. debuginfo-tests/
  5. libc/
  6. libclc/
  7. libcxx/
  8. libcxxabi/
  9. libunwind/
  10. lld/
  11. lldb/
  12. llvm/
  13. mlir/
  14. openmp/
  15. parallel-libs/
  16. polly/
  17. pstl/
  18. utils/
  19. .arcconfig
  20. .arclint
  21. .clang-format
  22. .clang-tidy
  23. .git-blame-ignore-revs
  24. .gitignore
  25. CONTRIBUTING.md
  26. 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.