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#//                     The LLVM Compiler Infrastructure
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#// This file is dual licensed under the MIT and the University of Illinois Open
#// Source Licenses. See LICENSE.txt for details.
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#//===----------------------------------------------------------------------===//
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==========================================================
How to Build the LLVM* OpenMP* Runtime Library using CMake
==========================================================

==== Version of CMake required: v2.8.0 or above ====
 
============================================
How to call cmake initially, then repeatedly
============================================
- When calling cmake for the first time, all needed compiler options
  must be specified on the command line.  After this initial call to
  cmake, the compiler definitions must not be included for further calls
  to cmake.  Other options can be specified on the command line multiple
  times including all definitions in the Build options section below.
- Example of configuring, building, reconfiguring, rebuilding:
  $ mkdir build
  $ cd build
  $ cmake -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DLIBOMP_ARCH=i386 ..  # Initial configuration
  $ make
  ...
  $ make clean
  $ cmake -DLIBOMP_ARCH=x86_64 -DCMAKE_BUILD_TYPE=Debug ..                       # Second configuration
  $ make
  ...
  $ rm -rf *
  $ cmake -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DLIBOMP_ARCH=x86_64 .. # Third configuration
  $ make
- Notice in the example how the compiler definitions are only specified
  for an empty build directory, but other Build options are used at any time.
- The file CMakeCache.txt which is created after the first call to cmake
  is a configuration file which holds all the values for the Build options.
  These configuration values can be changed using a text editor to modify 
  CMakeCache.txt as opposed to using definitions on the command line.
- To have cmake create a particular type of build generator file simply 
  inlude the -G <Generator name> option:
  $ cmake -G "Unix Makefiles" ...
  You can see a list of generators cmake supports by executing cmake with
  no arguments and a list will be printed.

=====================
Instructions to Build
=====================
 $ cd libomp_top_level/ [ directory with src/ , exports/ , tools/ , etc. ]
 $ mkdir build
 $ cd build

 [ Unix* Libraries ]
 $ cmake -DCMAKE_C_COMPILER=<C Compiler> -DCMAKE_CXX_COMPILER=<C++ Compiler> ..

 [ Intel(R) Many Integrated Core Library (Intel(R) MIC Library) ]
 $ cmake -DCMAKE_C_COMPILER=<C Compiler> -DCMAKE_CXX_COMPILER=<C++ Compiler> -DLIBOMP_ARCH=mic ..

 [ Windows Libraries ]
 $ cmake -G <Generator Type> -DCMAKE_C_COMPILER=<C Compiler> -DCMAKE_CXX_COMPILER=<C++ Compiler> -DCMAKE_ASM_MASM_COMPILER=[ml | ml64] -DCMAKE_BUILD_TYPE=Release ..

 $ make
 $ make install

==================
Mac* Fat Libraries
==================
On OS X* machines, it is possible to build universal (or fat) libraries which
include both i386 and x86_64 architecture objects in a
single archive.
 $ cmake -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_OSX_ARCHITECTURES='i386;x86_64' ..
 $ make
There is also an option -DLIBOMP_OSX_ARCHITECTURES which can be set in case
this is an LLVM source tree build which will only set the libomp library
to a universal fat library and prevent having the entire llvm/clang build
produce universal binaries.

===========
Micro tests
===========
After the library has been built, there are five optional microtests that
can be performed.  Some will be skipped based upon the platform.
To run the tests,
$ make libomp-micro-tests

=============
CMake options
=============
-DCMAKE_C_COMPILER=<C compiler name>
Specify the C compiler

-DCMAKE_CXX_COMPILER=<C++ compiler name>
Specify the C++ compiler

-DCMAKE_Fortran_COMPILER=<Fortran compiler name>
This option is only needed when -DLIBOMP_FORTRAN_MODULES is on.
So typically, a Fortran compiler is not needed during the build.
Specify the Fortran compiler

-DCMAKE_ASM_MASM_COMPILER=[ml | ml64 ]
This option is Windows* Only

-DLIBOMP_ARCH=i386|x86_64|arm|ppc64|ppc64le|aarch64|mic
The default for the option is chosen based on the probing the compiler for 
architecture macros (e.g., is __x86_64__ predefined by compiler?).

==== First values listed are the default value ====
-DLIBOMP_LIB_TYPE=normal|profile|stubs
Library type can be normal, profile, or stubs.

-DCMAKE_BUILD_TYPE=Release|Debug|RelWithDebInfo
Build type can be Release, Debug, or RelWithDebInfo.

-DLIBOMP_VERSION=5|4
libomp major version can be 5 or 4.

-DLIBOMP_OMP_VERSION=41|40|30
OpenMP version can be either 41, 40 or 30.

-DLIBOMP_MIC_ARCH=knc|knf
This value is ignored if LIBOMP_ARCH != mic
Intel(R) MIC Architecture, can be knf or knc.
  
-DLIBOMP_FORTRAN_MODULES=off|on
Should the Fortran modules be created (requires Fortran compiler)

-DLIBOMP_USE_ADAPTIVE_LOCKS=on|off       
Should adaptive (TSX-based) locks be included?  
These are x86 specific.  This feature is turned on by default 
for i386 and x86_64.  Otherwise, it is turned off.

-DLIBOMP_USE_INTERNODE_ALIGNMENT=off|on
Should 4096-byte alignment be used for certain data structures?
This option is useful on multinode systems where a small CACHE_LINE
setting leads to false sharing.  This option is off by default.

-DLIBOMP_USE_VERSION_SYMBOLS=on|off
Should versioned symbols be used for building the library?
This option only makes sense for ELF based libraries where version
symbols are supported (Linux, some BSD* variants).  It is off
by default for Windows and Mac, but on for other Unix based operating
systems.

-DLIBOMP_OMPT_SUPPORT=off|on
Should OMPT support be included in the build? (Not supported on Windows)
If LIBOMP_OMPT_SUPPORT is off, then both ompt_blame and ompt_trace are ignored.

-DLIBOMP_OMPT_BLAME=on|off
Should OMPT blame functionality be included in the build?

-DLIBOMP_OMPT_TRACE=on|off
Should OMPT trace functionality be included in the build?

-DLIBOMP_STATS=off|on
Should include stats-gathering code be included in the build?

-DLIBOMP_USE_DEBUGGER=off|on
Should the friendly debugger interface be included in the build?

================================
How to append flags to the build
================================
- These flags are *appended*.  They do not 
  overwrite any of the preset flags.
-DLIBOMP_CPPFLAGS=<space-separated flags> -- Additional C preprocessor flags
-DLIBOMP_CFLAGS=<space-separated flags>   -- Additional C compiler flags
-DLIBOMP_CXXFLAGS=<space-separated flags> -- Additional C++ compiler flags
-DLIBOMP_ASMFLAGS=<space-separated flags> -- Additional assembly flags
-DLIBOMP_LDFLAGS=<space-separated flags>  -- Additional linker flags
-DLIBOMP_LIBFLAGS=<space-separated flags> -- Additional libraries to link
-DLIBOMP_FFLAGS=<space-separated flags>   -- Additional Fortran compiler flags

=======================
Example usages of CMake
=======================
---- Typical usage ----
cmake -DCMAKE_C_COMPILER=icc -DCMAKE_CXX_COMPILER=icpc ..
cmake -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ ..
cmake -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ ..

---- With Various Options ----
- Build the i386 Linux library using GCC*
cmake -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DLIBOMP_ARCH=i386 ..

- Build the x86_64 debug Mac library using Clang*
cmake -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DLIBOMP_ARCH=x86_64 -DCMAKE_BUILD_TYPE=Debug ..

- Build the library (architecture determined by probing compiler) using the
  Intel(R) C Compiler and the Intel(R) C++ Compiler. Also, create the fortran modules using
  the Intel(R) Fortran Compiler.
cmake -DCMAKE_C_COMPILER=icc -DCMAKE_CXX_COMPILER=icpc -DCMAKE_Fortran_COMPILER=ifort -DLIBOMP_FORTRAN_MODULES=on ..

- Have CMake Find the C/C++ compiler, and specify additional flags for the C compiler, preprocessor, and C++ compiler.
cmake -DLIBOMP_CFLAGS='-specific-flag' -DLIBOMP_CPPFLAGS='-DNEW_FEATURE=1 -DOLD_FEATURE=0' -DLIBOMP_CXXFLAGS='--one-specific-flag --two-specific-flag' ..

---- Build the stubs library ----
cmake -DCMAKE_C_COMPILER=gcc -DCMAKE_CXX_COMPILER=g++ -DLIBOMP_LIB_TYPE=stubs ..

=========
Footnotes
=========
[*] Other names and brands may be claimed as the property of others.