def test_nested_block(self):
body = """
long x;
if (0 == 0) {
long x = 1;
}
"""
stms = parse_stm(body)
local_vars = get_local_vars(stms)
self.assertEqual(local_vars, ['x', 'x'])
def test_function(self):
body = """
long x;
long y = 1;
int m = 0;
if (x == 0) {
long z;
} else {
long t;
}
while (x == x) {
long a = 1;
}
"""
stms = parse_stm(body)
local_vars = get_local_vars(stms)
self.assertEqual(local_vars, ['x', 'y', 'm', 'z', 't', 'a'])
def visit_FunDecl(self, _type, name, params, body):
funname = mangle_fun(name)
# prepare the prologue
#
# at this moment [rsp] contains the return address
# [rsp] + 8 contains arg #1
# [rsp] + 16 contains arg #2
# etc
#
# We store rsp in rbp at the very start of the prologue
# so we can reference the vars using offsets of rbp.
#
# THIS ALSO MEANS THAT WE MUST ADD ANOTHER OFFSET OF 8!
# The stack looks like this:
# [rbp] == value of rsp
# [rbp + 8] == stored value of rbp
# [rbp + 16] == arg #1
# [rbp + 24] == arg #2
# etc!
#
# Note that the value of rsp changes as we change the stack.
# rbp is a callee-save register, so we don't have to worry
# about it being changed when calling other functions.
#
# Local variables are stored on the other side of rbp, ie:
# [rbp - 8] == first local variable
# [rbp - 16] == second local variable
# etc!
# Bind the parameters
word_len = 8
for i, param in enumerate(params):
var = param.var
index = i + 2
# offset = word_len * index
addr = VarAddr("rbp", MemOffset(Sign.Plus, word_len, index))
self.add_parameter_of_local(var, addr)
# Allocate local variables
local_vars = get_local_vars(body)
for i, var in enumerate(local_vars):
index = i + 1
addr = VarAddr("rbp", MemOffset(Sign.Minus, word_len, index))
self.add_parameter_of_local(var, addr)
# update the rsp to make space for local variables
locals_size = word_len * len(local_vars)
local_vars_add_space = f"sub rsp, {locals_size}"
local_vars_dec_space = f"add rsp, {locals_size}"
prologue = f"""
push rbp
mov rbp, rsp
{local_vars_add_space}
"""
# the epilogue label must be known here, because we need to jump here
# if we find any return
epilogue_lbl = f"{funname}_epilogue"
self.push_epilogue(epilogue_lbl)
# The main body of the function
# the result of the function call is the content of the rax register
body_code = self.visit_many(body)
# we pass the label as a correctness check
self.pop_epilogue(epilogue_lbl)
# prepare the epilogue
# NOTE: the parameters on the stack will be removed by the caller
epilogue = f"""
{local_vars_dec_space}
pop rbp
"""
# remove the bindings for the local vars:
for var in local_vars:
self.remove_parameter_or_local(var)
# remove the bindings for the params
for param in params:
self.remove_parameter_or_local(param.var)
return f"""