adding ability to build in llvm source tree, updated README

README.md

@@ -1,10 +1,36 @@
 # HIPIFY
 The CLANG-based HIPIFY tool - translates CUDA to [HIP](https://github.com/GPUOpen-ProfessionalCompute-Tools/HIP/blob/master/README.md)
 
-# How to Build
-- Get LLVM and CLANG sources and build CLANG, then install it to a **LLVM_INSTALL_PATH** folder
-- make build dir for hipify and run the folloing commands there:
+# How to Build *standalone* tool
+- Get LLVM and CLANG sources, build them and install to a **LLVM_INSTALL_PATH** folder
+- mkdir for hipify, run cmake there and build the tool:
 ```
-> cmake -DLLVM_DIR="LLVM_INSTALL_PATH" path_to_hipify_src
-> make
+git clone http://llvm.org/git/llvm.git llvm
+git clone http://llvm.org/git/clang.git llvm/tools/clang
+
+mkdir llvm_build && cd llvm_build
+cmake -DCMAKE_INSTALL_PREFIX="LLVM_INSTALL_PATH" -DLLVM_TARGETS_TO_BUILD="X86;NVPTX;AMDGPU" ../llvm
+make && make install
+
+git clone https://github.com/GPUOpen-ProfessionalCompute-Tools/HIP-hipify.git path_to_hipify_src
+mkdir path_to_hipify_src/build && cd path_to_hipify_src/build
+cmake -DLLVM_DIR="LLVM_INSTALL_PATH" -DHIPIFY_STANDLONE=1 ..
+make
 ```
+
+# How to Build tool *in llvm source tree*
+- get LLVM, CLANG and clang-tools-extra sources
+- put hipify folder into llvm/tools/clang/tools/extra, add it to llvm/tools/clang/tools/extra/CMakeLists.txt
+- run cmake and build tool
+```
+git clone http://llvm.org/git/llvm.git llvm
+git clone http://llvm.org/git/clang.git llvm/tools/clang
+git clone http://llvm.org/git/clang-tools-extra.git llvm/tools/clang/tools/extra
+git clone https://github.com/GPUOpen-ProfessionalCompute-Tools/HIP-hipify.git llvm/tools/clang/tools/extra/hipify
+echo "add_subdirectory(hipify)" >> llvm/tools/clang/tools/extra/CMakeLists.txt
+
+mkdir llvm_build && cd llvm_build
+cmake -DLLVM_TARGETS_TO_BUILD="X86;NVPTX;AMDGPU" ../llvm
+make -C tools/clang/tools/extra/hipify
+```
+