Updated main readme file

README.md

@@ -21,12 +21,14 @@ HPVM is currently at version 0.5. For more about what HPVM is, see [our website]
 ## Dependencies
 The following components are required to be installed on your machine to build HPVM.
 
-* GCC (>=5.1.0)
-* CMake (>=3.17.0)
-* Python (>=2.7)
-* GNU Make (>=3.79.1)
-* OpenCL (>=1.0.0) or CUDA (>=9.1, only required for GPU support)
-
+* GCC (>=5.1)
+  * In addition, each version of CUDA-nvcc requires GCC to be not newer than a certain version.
+    See [here](https://gist.github.com/ax3l/9489132) for the support matrix.
+* CMake (>=3.17)
+* Python (>=3.7) with Pip
+* GNU Make (>=3.79)
+* OpenCL (>=1.0.0)
+* CUDA (>=9.1)
 
 ## Supported Targets
 Supported/tested CPU architectures:
@@ -45,17 +47,20 @@ HPVM has not been tested but might work on other CPUs supported by LLVM Backend,
 
 Checkout HPVM:
 ```shell
-git clone https://gitlab.engr.illinois.edu/llvm/hpvm-release.git/
+git clone --recursive https://gitlab.engr.illinois.edu/llvm/hpvm-release.git/
 cd hpvm-release/hpvm
 ```
 
-Before installing HPVM, some paths must be set for installation to succeed. The following variables in set_paths.sh must be set:
+HPVM needs to be able to find CUDA.
+If CUDA is installed in your system's $PATH (e.g. if it was installed at the default location),
+HPVM can find CUDA automatically.
+Otherwise, some environment variables are required:
 
-* CUDA_TOOLKIT_PATH --- Path to the CUDA toolkit
-* CUDA_INCLUDE_PATH --- Path to the CUDA headers
-* CUDA_LIB_PATH -- Path to CUDA libraries 
+* `CUDA_TOOLKIT_PATH` --- Path to the CUDA toolkit
+* `CUDA_INCLUDE_PATH` --- Path to the CUDA headers
+* `CUDA_LIB_PATH` --- Path to CUDA libraries 
 
-Once the aforementioned variables in set_paths.sh have been specified, run the script.
+`hpvm/set_paths.sh` can be used for this. Modify the values of these variables in set_paths.sh and source the script:
 ```shell
 source set_paths.sh
 ```
@@ -78,6 +83,9 @@ mkdir build
 cd build
 cmake ../llvm [options]
 ```
+**Note** that if the installer script was not used,
+you must _manually add the build directory to your $PATH variable_.
+
 Some common options that can be used with CMake are:
 
 * -DCMAKE_INSTALL_PREFIX=directory --- Specify for directory the full pathname of where you want the HPVM tools and libraries to be installed.
@@ -112,5 +120,3 @@ We are also providing [unit tests](/hpvm/test/unitTests) and [regression tests](
 
 ## Support
 All questions can be directed to [hpvm-dev@lists.cs.illinois.edu](mailto:hpvm-dev@lists.cs.illinois.edu).
-
-