LLVMLite Function Pass manager example

llvmlite_fpm.py

__author__ = 'sarangis'

from ctypes import CFUNCTYPE, c_int
import sys

import llvmlite.ir as ll
import llvmlite.binding as llvm

llvm.initialize()
llvm.initialize_native_target()
llvm.initialize_native_asmprinter()

# Create a new module with a function implementing this:
#
# int sum(int a, int b) {
#   return a + b;
# }
def runOnFunction(module):
    print("In RunOnFunction")
    for f in module.functions:
        for bb in f: # Here I don't know how to manipulate instructions nor can i iterate over these.
            print(bb)

def main():
    module = ll.Module()
    func_ty = ll.FunctionType(ll.IntType(32), [ll.IntType(32), ll.IntType(32)])
    func = ll.Function(module, func_ty, name='sum')

    func.args[0].name = 'a'
    func.args[1].name = 'b'

    bb_entry = func.append_basic_block('entry')
    irbuilder = ll.IRBuilder(bb_entry)
    tmp = irbuilder.add(func.args[0], func.args[1])
    ret = irbuilder.ret(tmp)

    print('=== LLVM IR')
    print(module)

    # Convert textual LLVM IR into in-memory representation.
    llvm_module = llvm.parse_assembly(str(module))

    fpm = llvm.create_function_pass_manager(llvm_module)
    fpm.run(runOnFunction(llvm_module))

    tm = llvm.Target.from_default_triple().create_target_machine()

    # Compile the module to machine code using MCJIT
    with llvm.create_mcjit_compiler(llvm_module, tm) as ee:
        ee.finalize_object()
        print('=== Assembly')
        print(tm.emit_assembly(llvm_module))

        # Obtain a pointer to the compiled 'sum' - it's the address of its JITed
        # code in memory.
        cfptr = ee.get_pointer_to_function(llvm_module.get_function('sum'))

        # To convert an address to an actual callable thing we have to use
        # CFUNCTYPE, and specify the arguments & return type.
        cfunc = CFUNCTYPE(c_int, c_int, c_int)(cfptr)

        # Now 'cfunc' is an actual callable we can invoke
        res = cfunc(17, 42)
        print('The result is', res)

if __name__ == "__main__":
    main()