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David Green 7d9af03ff7 [Scheduling][ARM] Consistently enable PostRA Machine scheduling 
In the ARM backend, for historical reasons we have only some targets
using Machine Scheduling. The rest use the old list scheduler as they
are using itinaries and the list scheduler seems to produce better code
(and not crash running out of register on v6m codes). So whether to use
the MIScheduler or not is checked at runtime from the subtarget
features.

This is fine, except for post-ra scheduling. Whether to use the old
post-ra list scheduler or the post-ra machine schedule is decided as the
pass manager is set up, in arms case from a newly constructed subtarget.
Under some situations, like LTO, this won't include the correct cpu so
can pick the wrong option. This can have a surprising effect on
performance.

To fix that, this patch overrides targetSchedulesPostRAScheduling and
addPreSched2 in the ARM backend, adding _both_ post-ra schedulers and
picking at runtime which to execute. To pick between the two I've had to
add a enablePostRAMachineScheduler() method that normally returns
enableMachineScheduler() && enablePostRAScheduler(), which can be
overridden to enable just one of PostRAMachineScheduler vs
PostRAScheduler.

Thanks to David Penry for the identifying this problem.

Differential Revision: https://reviews.llvm.org/D69775
 		2019-11-05 10:44:55 +00:00
clang [OpenCL] Group builtin functions by prototype 2019-11-05 10:26:47 +00:00
clang-tools-extra [clang-tidy] New checker performance-trivially-destructible-check 2019-11-01 16:16:49 +01:00
compiler-rt Remove unused variables, as suggested by @mcgov. 2019-11-04 14:55:51 -05:00
debuginfo-tests [debuginfo-tests] Don't look for Python 3 if we already have it 2019-11-01 11:24:39 -07:00
libc Illustrate a redirector using the example of round function from math.h. 2019-11-01 11:06:12 -07:00
libclc [www] Change URLs to HTTPS. 2019-10-24 13:25:15 -07:00
libcxx Optimize std::midpoint for integers 2019-11-04 19:00:23 -08:00
libcxxabi [demangle] NFC: get rid of NodeOrString 2019-11-04 12:17:12 -08:00
libunwind build: explicitly set the linker language for unwind 2019-11-04 16:55:31 -08:00
lld ELF: Discard .ARM.exidx sections for empty functions instead of misordering them. 2019-11-04 09:11:14 -08:00
lldb lldb/breakpad: add suppport for the "x86_64h" architecture 2019-11-05 11:41:20 +01:00
llgo IR: Support parsing numeric block ids, and emit them in textual output. 2019-03-22 18:27:13 +00:00
llvm [Scheduling][ARM] Consistently enable PostRA Machine scheduling 2019-11-05 10:44:55 +00:00
openmp Test commit: adds a . to comment. NFC 2019-11-04 16:51:03 -06:00
parallel-libs Fix typos throughout the license files that somehow I and my reviewers 2019-01-21 09:52:34 +00:00
polly [www] Change URLs to HTTPS. 2019-10-24 13:25:15 -07:00
pstl [pstl] Allow customizing whether per-TU insulation is provided 2019-08-13 12:49:00 +00:00
.arcconfig Update monorepo .arcconfig with new project callsign. 2019-01-31 14:34:59 +00:00
.clang-format Add .clang-tidy and .clang-format files to the toplevel of the 2019-01-29 16:43:16 +00:00
.clang-tidy Disable tidy checks with too many hits 2019-02-01 11:20:13 +00:00
.git-blame-ignore-revs Add LLDB reformatting to .git-blame-ignore-revs 2019-09-04 09:31:55 +00:00
.gitignore Add a newline at the end of the file 2019-09-04 06:33:46 +00:00
README.md Add beginning of LLVM's GettingStarted to GitHub readme 2019-10-23 18:03:37 -07:00

README.md

The LLVM Compiler Infrastructure

This directory and its subdirectories contain source code for LLVM, a toolkit for the construction of highly optimized compilers, optimizers, and runtime environments.

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 workflow and configuration to get and build the LLVM source:

  1. Checkout LLVM (including related subprojects 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 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 subprojects 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 pathname 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).

    • Run your build tool of choice!

      • 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 build 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 make -j NNN (NNN is the number of parallel jobs, use e.g. 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.