[SYCL][DOC] Add build instructions for Windows to GetStartedWithSYCLCompiler.md

1. Fixed an error in cmake command for Linux.
2. Added steps for OpenCL-Headers and OpenCL-ICD-Loader components, which
are required.
3. Added Windows build instructions.
4. Made the build process more verbose and clear. You can literally follow
the guide step-by-step to build compiler and tools and run a simple test.

Signed-off-by: Vyacheslav N Klochkov <[email protected]>

Author: v-klochkov

sycl/doc/GetStartedWithSYCLCompiler.md

@@ -1,12 +1,12 @@
 # Overview
-
 The SYCL* Compiler compiles C++\-based SYCL source files with code for both CPU
 and a wide range of compute accelerators. The compiler uses Khronos*
 OpenCL™ API to offload computations to accelerators.
 
+
 # Before You Begin
 
-OpenCL runtime for CPU and/or GPU:
+### Get `OpenCL runtime` for CPU and/or GPU:
 
    a. OpenCL runtime for GPU: follow instructions on
 [github.com/intel/compute-runtime/releases](https://github.com/intel/compute-runtime/releases)
@@ -16,55 +16,156 @@ to install.
 SYCL support: follow the instructions under
 [SYCL* Compiler and Runtimes](https://github.com/intel/llvm/releases/tag/2019-07)
 
-# Build the SYCL compiler and runtime
+### Get the required tools:
+
+   a. `git` - for downloading the sources (Get it at https://git-scm.com/downloads)
+   
+   b. `cmake` - for building the compiler and tools, version 3.2 or later (Get it at: http://www.cmake.org/download)
+      
+   c. `python` - for building the compiler and running tests (Get it at: https://www.python.org/downloads/release/python-2716/ )
+
+   d. `Visual Studio 2017 or later` (Windows only. Get it at: https://visualstudio.microsoft.com/downloads/)
+
+
+# Configure environment:
+For simplicity it is assumed below that the environment variable SYCL_HOME contains path to a folder where the SYCL compiler and runtime will be stored.
+### Linux:
+```bash
+export SYCL_HOME=/export/home/workspaces/sycl_workspace
+mkdir $SYCL_HOME
+```
+### Windows:
+Open a developer command prompt using one of tho methods:
+- Click start menu and search for the command prompt. So, for MSVC-2017 it is '`x64 Native Tools Command Prompt for VS 2017`'
+- run 'cmd' and then '`"C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvarsall.bat" x64`'
+
+```bash
+set SYCL_HOME=%USERPROFILE%\workspaces\sycl_workspace
+mkdir %SYCL_HOME%
+```
+# Get `OpenCL-Headers` and `OpenCL-ICD-Loader`
+
+**These 2 steps are optional.** The Compiler build process is going to look for available OpenCL SDK on the local machine.
+If it finds suitable OpenCL, it will reuse it. Otherwise, it will automatically download `OpenCL-Headers` and `OpenCL-ICD-Loader` from GitHub and build it.
+You may want to run these steps if have some unexpected problems caused by `OpenCL-Headers` or `OpenCL-ICD-Loader` at the compiler build phase.
+
+## Get `OpenCL-Headers`
+### Linux:
+```bash
+cd $SYCL_HOME
+git clone https://github.com/KhronosGroup/OpenCL-Headers
+export OPENCL_HEADERS=$SYCL_HOME/OpenCL-Headers
+```
+
+ ### Windows:
+```bash
+cd %SYCL_HOME%
+git clone https://github.com/KhronosGroup/OpenCL-Headers
+set OPENCL_HEADERS=%SYCL_HOME%\OpenCL-Headers
+```
 
-Download the LLVM* repository with SYCL support to your local machine folder
-e.g. `$HOME/sycl` (assuming environment var `$SYCL_HOME`) folder using
-following command:
+## Get `OpenCL-ICD-Loader`
+You can also find the most recent instructions for this component at https://github.com/KhronosGroup/OpenCL-ICD-Loader
+
+### Linux:
+```bash
+cd $SYCL_HOME
+git clone https://github.com/KhronosGroup/OpenCL-ICD-Loader
+cd OpenCL-ICD-Loader
+mkdir build
+cd build
+cmake -DOPENCL_ICD_LOADER_HEADERS_DIR=$OPENCL_HEADERS ..
+make
+export ICD_LIB=$SYCL_HOME/OpenCL-ICD-Loader/build/libOpenCL.so
+```
 
+### Windows:
 ```bash
-git clone https://github.com/intel/llvm -b sycl $HOME/sycl
+cd %SYCL_HOME%
+git clone https://github.com/KhronosGroup/OpenCL-ICD-Loader
+cd OpenCL-ICD-Loader
+mkdir build
+cd build
+cmake -G "Ninja" -DOPENCL_ICD_LOADER_HEADERS_DIR=%OPENCL_HEADERS% -DOPENCL_ICD_LOADER_REQUIRE_WDK=OFF ..
+ninja
+set ICD_LIB=%SYCL_HOME%\OpenCL-ICD-Loader\build\OpenCL.lib
 ```
 
-Build the SYCL compiler and runtime following instruction below:
+# Checkout and Build the SYCL compiler and runtime
+
+Defining paths to `OpenCL-Headers` and `OpenCL-ICD-Loader` is optional ( `-DOpenCL_INCLUDE_DIR=` and `-DOpenCL_LIBRARY=` ).
+If you do not specify the paths explicitly, then:
+- If `OpenCL-Headers` and `OpenCL-ICD-Loader` are availalbe in the system, they will be used;
+- If they are not available, then OpenCL files are automatically downloaded/built from GitHub during compiler build.
 
+### Linux:
 ```bash
+cd $SYCL_HOME
+git clone https://github.com/intel/llvm -b sycl
 mkdir $SYCL_HOME/build
 cd $SYCL_HOME/build
-cmake -DCMAKE_BUILD_TYPE=Release \
+
+cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_TARGETS_TO_BUILD="X86" \
 -DLLVM_EXTERNAL_PROJECTS="llvm-spirv;sycl" \
--DLLVM_EXTERNAL_SYCL_SOURCE_DIR=$SYCL_HOME/sycl \
--DLLVM_EXTERNAL_LLVM_SPIRV_SOURCE_DIR=$SYCL_HOME/llvm-spirv \
 -DLLVM_ENABLE_PROJECTS="clang;llvm-spirv;sycl" \
-$SYCL_HOME/llvm
+-DLLVM_EXTERNAL_SYCL_SOURCE_DIR=$SYCL_HOME/llvm/sycl \
+-DLLVM_EXTERNAL_LLVM_SPIRV_SOURCE_DIR=$SYCL_HOME/llvm/llvm-spirv \
+-DOpenCL_INCLUDE_DIR="$OPENCL_HEADERS" -DOpenCL_LIBRARY="$ICD_LIB" \
+$SYCL_HOME/llvm/llvm
+
 make -j`nproc` sycl-toolchain
 ```
+### Windows:
+```bash
+mkdir %SYCL_HOME%
+cd %SYCL_HOME%
+git clone https://github.com/intel/llvm -b sycl
+mkdir %SYCL_HOME%\build
+cd %SYCL_HOME%\build
+
+cmake -G "Ninja" -DCMAKE_BUILD_TYPE=Release -DLLVM_TARGETS_TO_BUILD="X86" -DLLVM_EXTERNAL_PROJECTS="llvm-spirv;sycl" -DLLVM_ENABLE_PROJECTS="clang;llvm-spirv;sycl" -DLLVM_EXTERNAL_SYCL_SOURCE_DIR="%SYCL_HOME%\llvm\sycl" -DLLVM_EXTERNAL_LLVM_SPIRV_SOURCE_DIR="%SYCL_HOME%\llvm\llvm-spirv" -DCMAKE_C_COMPILER=cl -DCMAKE_CXX_COMPILER=cl -DCMAKE_C_FLAGS="/GS" -DCMAKE_CXX_FLAGS="/GS" -DCMAKE_EXE_LINKER_FLAGS="/NXCompat /DynamicBase" -DCMAKE_SHARED_LINKER_FLAGS="/NXCompat /DynamicBase" -DOpenCL_INCLUDE_DIR="%OPENCL_HEADERS%" -DOpenCL_LIBRARY="%ICD_LIB%" "%SYCL_HOME%\llvm\llvm"
+
+ninja sycl-toolchain
+```
 
 After the build completed, the SYCL compiler/include/libraries can be found
-under `$SYCL_HOME/build` directory.
+in `$SYCL_HOME/build` directory.
+
+---
 
 ## Build the SYCL runtime with libc++ library.
 
 There is experimental support for building and linking SYCL runtime with
 libc++ library instead of libstdc++. To enable it the following cmake options
-should be used:
-
+should be used.
+### Linux:
 ```
 -DSYCL_USE_LIBCXX=ON \
 -DSYCL_LIBCXX_INCLUDE_PATH=<path to libc++ headers> \
 -DSYCL_LIBCXX_LIBRARY_PATH=<path to libc++ and libc++abi libraries>
 ```
-
 # Test the SYCL compiler and runtime
 
-Run LIT testing using the command below after building SYCL compiler and runtime.
-
+After building the SYCL compiler and runtime, choose the amount of LIT testing you need and run one of the LIT tests suites shown below:
+### Linux:
 ```bash
-make -j`nproc` check-all
+make -j`nproc` check-all        # to run all test suites including those smaller ones shown below
+make -j`nproc` check-llvm       # run llvm tests only
+make -j`nproc` check-llvm-spirv # run llvm-spirv tests only
+make -j`nproc` check-clang      # run clang tests only
+make -j`nproc` check-sycl       # run sycl tests only
+```
+### Windows:
+```bash
+ninja check-all
+ninja check-llvm
+ninja check-llvm-spirv
+ninja check-clang
+ninja check-sycl
 ```
 If no OpenCL GPU/CPU runtimes are available, the corresponding LIT tests are skipped
 
-# Creating a simple SYCL program
+# Create a simple SYCL program
 
 A simple SYCL program consists of following parts:
 1. Header section
@@ -78,7 +179,6 @@ A simple SYCL program consists of following parts:
 Creating a file `simple-sycl-app.cpp` with the following C++ SYCL code in it:
 
 ```c++
-
 #include <CL/sycl.hpp>
 
 int main() {
@@ -129,21 +229,34 @@ int main() {
 
 # Build and Test a simple SYCL program
 
-To build simple-sycl-app run following command:
+To build simple-sycl-app put `bin` and `lib` to PATHs and run following command:
+### Linux:
+   ```bash
+   export PATH=$SYCL_HOME/build/bin:$PATH
+   export LD_LIBRARY_PATH=$SYCL_HOME/build/lib:$LD_LIBRARY_PATH
+   ```
+### Windows:
+   ```bash
+   set PATH=%SYCL_HOME%\build\bin;%PATH%
+   set LIB=%SYCL_HOME%\build\lib;%LIB%
+   ```
 
-   ```console
-   clang++ -std=c++11 -fsycl simple-sycl-app.cpp -o simple-sycl-app -lOpenCL
+### Linux & Windows:
+   ```bash
+   clang++ -fsycl simple-sycl-app.cpp -o simple-sycl-app.exe -lOpenCL
    ```
 
-This `simple-sycl-app` application doesn't specify SYCL device for execution,
+This `simple-sycl-app.exe` application doesn't specify SYCL device for execution,
 so SYCL runtime will first try to execute on OpenCL GPU device first, if OpenCL
 GPU device is not found, it will try to run OpenCL CPU device; and if OpenCL
 CPU device is also not available, SYCL runtime will run on SYCL host device.
 
-To run the `simple-sycl-app`:
+### Linux & Windows:
+   ```bash
+   ./simple-sycl-app.exe
+   The results are correct!
+   ```
 
-    LD_LIBRARY_PATH=$SYCL_HOME/build/lib ./simple-sycl-app
-    The results are correct!
 
 NOTE: SYCL developer can specify SYCL device for execution using device
 selectors (e.g. `cl::sycl::cpu_selector`, `cl::sycl::gpu_selector`) as
@@ -194,6 +307,8 @@ int main() {
 
 ```
 
+# C++ standard
+- Minimally support C++ standard is c++11 on Linux and c++14 on Windows.
 
 # Known Issues or Limitations
 
@@ -202,8 +317,6 @@ int main() {
 - SYCL host device is not fully supported.
 - SYCL works only with OpenCL implementations supporting out-of-order queues.
 
-
 # Find More
 
 SYCL 1.2.1 specification: [www.khronos.org/registry/SYCL/specs/sycl-1.2.1.pdf](https://www.khronos.org/registry/SYCL/specs/sycl-1.2.1.pdf)
-