compilation-process.rst

HPVM Compilation Process

Compilation of an HPVM program involves the following steps:

1. clang takes an HPVM-C/C++ program (e.g. main.c) and produces an LLVM IR (main.ll) file that contains the HPVM-C function calls. The declarations of these functions are defined in test/benchmark/include/hpvm.h, which must be included in the program.
2. opt takes (main.ll) and invoke the GenHPVM pass on it, which converts the HPVM-C function calls to HPVM intrinsics. This generates the HPVM textual representation (main.hpvm.ll).
3. opt takes the HPVM textual representation (main.hpvm.ll) and invokes the following passes in sequence:
   • BuildDFG: Converts the textual representation to the internal HPVM representation.
   • LocalMem and DFG2LLVM_OpenCL: Invoked only when GPU target is selected. Generates the kernel module (main.kernels.ll) and the portion of the host code that invokes the kernel into the host module (main.host.ll).
   • DFG2LLVM_CPU: Generates either all, or the remainder of the host module (main.host.ll) depending on the chosen target.
   • ClearDFG: Deletes the internal HPVM representation from memory.
4. clang is used to to compile any remaining project files that would be later linked with the host module.
5. llvm-link takes the host module and all the other generate ll files, and links them with the HPVM runtime module (hpvm-rt.bc), to generate the linked host module (main.host.linked.ll).
6. Generate the executable code from the generated ll files for all parts of the program:
   • GPU target: llvm-cbe takes the kernel module (main.kernels.ll) and generates an OpenCL representation of the kernels that will be invoked by the host.
   • CPU target: clang takes the linked host module (main.host.linked.ll) and generates the CPU binary.