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Philip Reames ef51eed37b [LoopDeletion] Handle inner loops w/untaken backedges 
This builds on the restricted after initial revert form of D93906, and adds back support for breaking backedges of inner loops. It turns out the original invalidation logic wasn't quite right, specifically around the handling of LCSSA.

When breaking the backedge of an inner loop, we can cause blocks which were in the outer loop only because they were also included in a sub-loop to be removed from both loops. This results in the exit block set for our original parent loop changing, and thus a need for new LCSSA phi nodes.

This case happens when the inner loop has an exit block which is also an exit block of the parent, and there's a block in the child which reaches an exit to said block without also reaching an exit to the parent loop.

(I'm describing this in terms of the immediate parent, but the problem is general for any transitive parent in the nest.)

The approach implemented here involves a potentially expensive LCSSA rebuild.  Perf testing during review didn't show anything concerning, but we may end up needing to revert this if anyone encounters a practical compile time issue.

Differential Revision: https://reviews.llvm.org/D94378
 		2021-01-22 16:31:29 -08:00
.github [github] Move repo lockdown config into llvm-project repo 2021-01-11 16:20:08 -08:00
clang ADT: Use 'using' to inherit assign and append in SmallString 2021-01-22 16:17:58 -08:00
clang-tools-extra [clangd] Inject context provider rather than config into ClangdServer. NFC 2021-01-22 14:34:30 +01:00
compiler-rt [MSan] Move origins for overlapped memory transfer 2021-01-21 02:11:26 +00:00
debuginfo-tests [DebugInfo][dexter] Tweak dexter test for merged values 2021-01-19 12:45:31 +00:00
flang [flang][nfc] Fix comments, remove needless API, tweak script 2021-01-22 10:55:53 -08:00
libc [libc] Distinguish compiler and run failures 2021-01-21 15:27:34 -08:00
libclc libclc: Use find_package to find Python 3 and require it 2020-10-01 22:31:33 +02:00
libcxx [libc++] Introduce __bits 2021-01-22 21:20:23 +01:00
libcxxabi [libc++abi] Simplify scan_eh_tab 2021-01-21 15:19:23 -08:00
libunwind [CMake] Remove dead code setting policies to NEW 2021-01-19 17:19:36 +02:00
lld [lld-macho] Ignore -lto_library 2021-01-22 16:48:50 -05:00
lldb Change static buffer to be BSS instead of DATA in HandlePacket_qSpeedTest 2021-01-22 16:14:24 -08:00
llvm [LoopDeletion] Handle inner loops w/untaken backedges 2021-01-22 16:31:29 -08:00
mlir [mlir][Linalg] Make Fill operation work on tensors. 2021-01-22 14:39:27 -08:00
openmp [libomptarget] Build cuda plugin without cuda installed locally 2021-01-23 00:15:04 +00:00
parallel-libs Reapply "Try enabling -Wsuggest-override again, using add_compile_options instead of add_compile_definitions for disabling it in unittests/ directories." 2020-07-22 17:50:19 -07:00
polly [polly][NewPM][test] Fix polly tests under -enable-new-pm 2021-01-19 12:38:58 -08:00
pstl [pstl] Replace direct use of assert() with _PSTL_ASSERT 2020-11-02 18:35:54 -05:00
runtimes [MSVC] Don't add -nostdinc++ -isystem to runtimes builds 2021-01-15 13:22:07 -08:00
utils/arcanist Fix arc lint's clang-format rule: only format the file we were asked to format. 2020-10-11 14:24:23 -07:00
.arcconfig Set the target branch for `arc land` to main 2020-12-07 21:57:32 +00:00
.arclint PR46997: don't run clang-format on clang's testcases. 2020-08-04 17:53:25 -07:00
.clang-format
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.clang-tidy - Update .clang-tidy to ignore parameters of main like functions for naming violations in clang and llvm directory 2020-01-31 16:49:45 +00:00
.git-blame-ignore-revs NFC: Add whitespace-changing revisions to .git-blame-ignore-revs 2020-09-21 20:17:24 -04:00
.gitignore [NFC] Add CMakeUserPresets.json filename to .gitignore 2021-01-22 12:45:29 +01:00
CONTRIBUTING.md
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README.md Revert "This is a test commit" 2020-10-21 09:34:15 +08:00

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.