def handle_move(self, label, result, *operands):
"""Handles the move instruction of IR.
"""
source = operands[0]
# If both the operands are memory locations, use %r15 as an intermediate
# register
if isinstance(source, Memory) and isinstance(operands[1], Memory):
r15 = Register()
r15.color = 13
mov = MOV(r15, operands[0])
self.add_instruction(label, mov)
source = r15
mov = MOV(operands[1], source)
self.add_instruction(label, mov)
def handle_ret(self, label, result, *operands):
"""Handles the return instruction of IR.
"""
# Return is nothing but the jump to the end of the function.
# If it has an operand it should be returned in %rax, according to Linux
# Application Binary Interface (ABI).
if operands:
# 0 is the Register color for %rax.
if operands[0]:
# Create a dummy register for %rax.
rax = Register()
rax.color = 0
mov = MOV(rax, operands[0])
self.add_instruction(label, mov)
jmp = JMP()
self.add_instruction(label, jmp)
self.returns_to_process.append(jmp)
def create_stack(self):
"""Creates the stack with the current memory offset value.
"""
# Create a dummy register and give it a color to keep the API consistent.
rbp = Register()
rbp.color = 'rbp' # The color of %rbp
push = PUSH(rbp)
self.add_instruction(0, push)
# Another dummy register for %rsp
rsp = Register()
rsp.color = 'rsp'
mov = MOV(rbp, rsp)
self.add_instruction(0, mov)
if self.memory_offset:
# Allocate memory for locals
sub = SUB(rsp, Immediate(self.memory_offset))
self.add_instruction(0, sub)
def entry():
"""Returns the precompiled code for starting the code.
"""
call = CALL()
# Move exit status to %rdi
rdi = Register()
rdi.color = 5
mov_status = MOV(rdi, Immediate(0))
# Move exit SYSCALL descriptor number to %rax
rax = Register()
rax.color = 0
mov_sycall = MOV(rax, Immediate(60))
# Make syscall
syscall = SYSCALL()
return (len(call) + len(mov_status) + len(mov_sycall)
+ len(syscall), [call, mov_status, mov_sycall, syscall])
def handle_cmp(self, label, result, *operands):
"""Handles the cmp instruction of IR.
"""
dest = operands[0]
if isinstance(operands[0], Memory) and isinstance(operands[1], Memory):
mov = MOV(result, operands[0])
self.add_instruction(label, mov)
dest = result
elif isinstance(operands[0], Immediate):
# FIXME: If the destination is an immediate operand, this is moved to
# a temporary scratch register and then compared, however this calls for
# a better mechanism. Please see issue #6.
r15 = Register()
r15.color = 13
mov = MOV(r15, operands[0])
self.add_instruction(label, mov)
dest = r15
cmp_instruction = CMP(dest, operands[1])
self.add_instruction(label, cmp_instruction)
def handle_store(self, label, result, *operands):
"""Handles the store instruction of IR.
"""
if isinstance(operands[1], Immediate) and isinstance(operands[2], Memory):
memory = Memory(
base=operands[2].base,
offset=operands[2].offset + (operands[1].value * MEMORY_WIDTH))
elif isinstance(operands[1], Register):
memory = Memory()
memory.base = operands[2]
memory.offset = operands[1]
elif isinstance(operands[1], Memory):
memory = operands[1]
memory.offset = self.memory_offset
self.memory_offset += MEMORY_WIDTH
if isinstance(operands[0], Memory) or (isinstance(operands[0], Register)
and isinstance(operands[0].color, Memory)):
# Take the set difference
free_registers = (REGISTERS_COLOR_SET -
set(self.instruction_live_registers[label].keys()))
if free_registers:
# Create a dummy register for this color
register = Register()
# pop and add back since sets don't support indexing
register.color = free_registers.pop()
free_registers.add(register.color)
mov1 = MOV(register, operands[0])
self.add_instruction(label, mov1)
mov2 = MOV(memory, register)
self.add_instruction(label, mov2)
else:
# We don't have any free registers :(
# We can't do much, randomly pick a register, push it to the stack,
# do the memory move from the source to this register and then use
# this register to move the source to the destination and then
# pop back our register.
# NOTE: We pick %rax for this temporary operation
# Create a dummy register for %rax
register = Register()
register.color = 0
push = PUSH(register)
self.add_instruction(label, push)
mov1 = MOV(register, operands[0])
self.add_instruction(label, mov1)
mov2 = MOV(memory, register)
self.add_instruction(label, mov2)
pop = POP(register)
self.add_instruction(label, pop)
else:
register = operands[0]
mov = MOV(memory, register)
self.add_instruction(label, mov)
def handle_div(self, label, result, *operands):
"""Handles the div instruction of IR.
"""
restore_rax = True
restore_rdx = True
# This will be true only if the second operand is immediate.
restore_r15 = False
# Create dummy register objects for RAX and RDX and force color them to
# ensure they take RAX and RDX values. So we can spill these two registers.
# Also create memory object to where they get spilled.
if self.is_register(result):
if result.color == 0:
restore_rax = False
elif result.color == 3:
restore_rdx = False
# We may want %rax register to move the first dividend to %rax if it is
# not already in %rax, so create a dummy %rax register in any case.
rax = Register()
rax.color = 0 # Color of RAX
# We want to clear the contents of %rdx no matter what, so create a dummy
# register for it.
rdx = Register()
rdx.color = 3 # Color of RDX
# Store %rax and %rdx in memory if they have to be restored
if restore_rax:
rax.memory = Memory()
rax_operands = (rax, rax.memory)
self.handle_store(label, None, *rax_operands)
if restore_rdx:
rdx.memory = Memory()
rdx_operands = (rdx, rdx.memory)
self.handle_store(label, None, *rdx_operands)
if not (self.is_register(operands[0]) and operands[0].color == 0):
mov = MOV(rax, operands[0])
self.add_instruction(label, mov)
# Clear %rdx, because x86_64 DIV instruction uses both %rax and %rdx as
# the divisor
xor = XOR(rdx, rdx)
self.add_instruction(label, xor)
if isinstance(operands[1], Immediate):
# Create a dummy register object for %r15 for moving the operand to it.
r15 = Register()
r15.color = 13
if not(self.is_register(result) and result.color == 13):
restore_r15 = True
r15.memory = Memory()
r15_operands = (r15, r15.memory)
self.handle_store(label, None, *r15_operands)
mov = MOV(r15, operands[1])
self.add_instruction(label, mov)
idiv = IDIV(r15)
else:
idiv = IDIV(operands[1])
self.add_instruction(label, idiv)
mov = MOV(result, rax)
self.add_instruction(label, mov)
if restore_rax:
self.handle_load(label, rax, rax.memory)
if restore_rdx:
self.handle_load(label, rdx, rdx.memory)
if restore_r15:
self.handle_load(label, r15, r15.memory)
def handle_call(self, function_name, label, result, *operands):
"""Handles the call instruction of IR.
"""
pushed_registers = []
if 0 in self.instruction_live_registers[label]:
self.instruction_live_registers[label].pop(0)
if not self.is_register(result) or result.color != 0:
# Create a dummy register
register = Register()
register.color = 0
push = PUSH(register)
self.add_instruction(label, push)
pushed_registers.append(register)
for register_color in self.instruction_live_registers[label]:
# Create a dummy register
register = Register()
register.color = register_color
push = PUSH(register)
self.add_instruction(label, push)
pushed_registers.append(register)
# Arguments are passed through %rdi, %rsi, %rdx, %rcx, %r8, %r9
for argument, register_color in zip(operands, FUNCTION_ARGUMENTS_COLORS):
if not (isinstance(argument, Register) and
argument.color == register_color):
# Create a dummy register for %rax.
new_register = Register()
new_register.color = register_color
mov = MOV(new_register, argument)
self.add_instruction(label, mov)
# If there are more than arguments to the function, push them on to the
# stack in the right-to-left order
if len(operands) > 6:
# Note we run this upto 5 but not including 5 which is the 6th argument.
for argument in operands[-1:5:-1]:
push = PUSH(argument)
self.add_instruction(label, push)
call = CALL()
self.add_instruction(label, call)
self.calls_to_link.append((call, function_name))
# Popping should be in the reverse order
pop_rax_later = False
for register in pushed_registers[-1::-1]:
# Don't pop %rax yet, if result exists, we need to mov %rax to
# actual result register and then pop
if register.color == 0:
pop_rax_later = True
continue
pop = POP(register)
self.add_instruction(label, pop)
# NOTE: The following move is done after popping all the values because
# popping overwrites the values otherwise.
# If the result of the call instruction is to be passed on to some other
# register than %rax, we need to insert a move for it.
if self.is_register(result) and result.color != 0:
rax = Register()
rax.color = 0
mov = MOV(result, rax)
self.add_instruction(label, mov)
# We should pop_rax if we rax has been pushed to the stack, but we can only
# pop it after moving the result to the right location.
if pop_rax_later:
register = Register()
register.color = 0
pop = POP(register)
self.add_instruction(label, pop)