Add a couple of examples with opaque pointers

This patch adds a couple of examples on how to use the new opaque
pointer builder interfaces. The examples are based on the already
existing examples with the same name.

Author: rj-jesus

examples/opaque_pointers/llvmir.py

@@ -0,0 +1,38 @@
+import llvmlite
+llvmlite.opaque_pointers_enabled = True
+
+import llvmlite.ir as ll
+
+fntype = ll.FunctionType(ll.IntType(32), [ll.IntType(32), ll.IntType(32)])
+
+module = ll.Module()
+
+func = ll.Function(module, fntype, name='foo')
+bb_entry = func.append_basic_block()
+
+builder = ll.IRBuilder()
+builder.position_at_end(bb_entry)
+
+stackint = builder.alloca(ll.IntType(32))
+# Instead of stackint.type.pointee we can access stackint.allocated_type
+# directly.
+builder.store(ll.Constant(stackint.allocated_type, 123), stackint)
+myint = builder.load(stackint)
+
+addinstr = builder.add(func.args[0], func.args[1])
+mulinstr = builder.mul(addinstr, ll.Constant(ll.IntType(32), 123))
+pred = builder.icmp_signed('<', addinstr, mulinstr)
+builder.ret(mulinstr)
+
+bb_block = func.append_basic_block()
+builder.position_at_end(bb_block)
+
+bb_exit = func.append_basic_block()
+
+pred = builder.trunc(addinstr, ll.IntType(1))
+builder.cbranch(pred, bb_block, bb_exit)
+
+builder.position_at_end(bb_exit)
+builder.ret(myint)
+
+print(module)

examples/opaque_pointers/sum.py

@@ -0,0 +1,115 @@
+from __future__ import print_function
+
+from ctypes import CFUNCTYPE, c_int, POINTER
+import sys
+try:
+    from time import perf_counter as time
+except ImportError:
+    from time import time
+
+import numpy as np
+
+try:
+    import faulthandler; faulthandler.enable()
+except ImportError:
+    pass
+
+import llvmlite
+llvmlite.opaque_pointers_enabled = True
+
+import llvmlite.ir as ll
+import llvmlite.binding as llvm
+
+
+llvm.initialize()
+llvm.initialize_native_target()
+llvm.initialize_native_asmprinter()
+
+
+t1 = time()
+
+# Pointers are opaque, so we should define them as such here.
+fnty = ll.FunctionType(ll.IntType(32), [ll.PointerType(), ll.IntType(32)])
+module = ll.Module()
+
+func = ll.Function(module, fnty, name="sum")
+
+bb_entry = func.append_basic_block()
+bb_loop = func.append_basic_block()
+bb_exit = func.append_basic_block()
+
+builder = ll.IRBuilder()
+builder.position_at_end(bb_entry)
+
+builder.branch(bb_loop)
+builder.position_at_end(bb_loop)
+
+index = builder.phi(ll.IntType(32))
+index.add_incoming(ll.Constant(index.type, 0), bb_entry)
+accum = builder.phi(ll.IntType(32))
+accum.add_incoming(ll.Constant(accum.type, 0), bb_entry)
+
+# These GEP and load need an excplicit type.
+ptr = builder.gep(func.args[0], [index], source_etype=ll.IntType(32))
+value = builder.load(ptr, typ=ll.IntType(32))
+
+added = builder.add(accum, value)
+accum.add_incoming(added, bb_loop)
+
+indexp1 = builder.add(index, ll.Constant(index.type, 1))
+index.add_incoming(indexp1, bb_loop)
+
+cond = builder.icmp_unsigned('<', indexp1, func.args[1])
+builder.cbranch(cond, bb_loop, bb_exit)
+
+builder.position_at_end(bb_exit)
+builder.ret(added)
+
+strmod = str(module)
+
+t2 = time()
+
+print("-- generate IR:", t2-t1)
+
+t3 = time()
+
+llmod = llvm.parse_assembly(strmod)
+
+t4 = time()
+
+print("-- parse assembly:", t4-t3)
+
+print(llmod)
+
+pmb = llvm.create_pass_manager_builder()
+pmb.opt_level = 2
+pm = llvm.create_module_pass_manager()
+pmb.populate(pm)
+
+t5 = time()
+
+pm.run(llmod)
+
+t6 = time()
+
+print("-- optimize:", t6-t5)
+
+t7 = time()
+
+target_machine = llvm.Target.from_default_triple().create_target_machine()
+
+with llvm.create_mcjit_compiler(llmod, target_machine) as ee:
+    ee.finalize_object()
+    cfptr = ee.get_function_address("sum")
+
+    t8 = time()
+    print("-- JIT compile:", t8 - t7)
+
+    print(target_machine.emit_assembly(llmod))
+
+    cfunc = CFUNCTYPE(c_int, POINTER(c_int), c_int)(cfptr)
+    A = np.arange(10, dtype=np.int32)
+    res = cfunc(A.ctypes.data_as(POINTER(c_int)), A.size)
+
+    print(res, A.sum())
+