def _recover(self, pseudo_register):
""" Handles the logic for reversing the spilling of a register.
:param pseudo_register: The name of the pseudo-register whose spilled value is being recovered.
:return: A tuple containing the physical register and a list of the MIPS code required to free the physical
register for use.
"""
spill_offset = self.spilled_registers.pop(pseudo_register)
physical_register = None
code = [
mi.COMMENT("recovering pseudo-register {}".format(pseudo_register))
]
if self.available_registers:
physical_register = self.available_registers.pop()
self.lru_cache[pseudo_register] = physical_register
else:
self.lru_cache[pseudo_register] = None
physical_register = self._freed_physical_register
code.extend(self._spill_code)
self.lru_cache[pseudo_register] = physical_register
code.append(
mi.LW(physical_register, mi.offset_label_immediate(self.spill_mem_base_label, spill_offset)))
self.available_spill_memory_words.append(spill_offset)
return physical_register, code
def _spill(self, pseudo_register, physical_register):
""" A private method for handling the logic for spilling the contents of a physical register into memory.
Since this method is used as a callback, it cannot return things in the traditional sense. Because of this, the
"returned" code and physical register are set to two private class variables, so the programmer must take care
to manage these variables appropriately.
:param pseudo_register: The name of the pseudo-register to be spilled. Aka 'key' for the purposes of the
pylru.lrucache callback.
:physical_register: The name of the physical register to be freed/reused. Aka 'value' for the purposes of the
pylru.lrucache callback.
:return: None.
"""
self._spill_code = []
self._freed_physical_register = physical_register
if not self.available_spill_memory_words:
print(self)
raise OutOfSpillMemoryException()
spill_offset = self.available_spill_memory_words.pop()
self.spilled_registers[pseudo_register] = spill_offset
self._spill_code = [
mi.COMMENT("spilling psuedo-register {} to free {}".format(pseudo_register, physical_register)),
mi.SW(physical_register, mi.offset_label_immediate(self.spill_mem_base_label, spill_offset)),
mi.COMMENT("spill complete")
]
def test_spill_recovery(self):
pseudo_registers = [INT_REGISTER_TICKETS.get() for _ in range(0, 3)]
self.register_use_table.acquire(pseudo_registers[0])
self.register_use_table.acquire(pseudo_registers[1])
self.assertSequenceEqual([], self.register_use_table.available_registers, 'the registers should be used up')
expected_result = {'register': mips.T0, 'code': [assembler.SW(mips.T0, assembler.offset_label_immediate(SPILL_MEM_LABEL, 0))]}
result = self.register_use_table.acquire(pseudo_registers[2])
self.assertEqual(expected_result, result)
# recovering a spilled register's value from memory should not only get the register, but also provide the
# mips code that swaps the values for the temporaries using the spill memory
expected_result = {'register': mips.T1, 'code': [assembler.SW(mips.T1, assembler.offset_label_immediate(SPILL_MEM_LABEL, 4)),
assembler.LW(mips.T1, assembler.offset_label_immediate(SPILL_MEM_LABEL, 0))]}
result = self.register_use_table.acquire(pseudo_registers[0])
self.assertEqual(expected_result, result)
def test_multiple_recoveries(self):
spilled_1 = 'ireg_1'
spilled_2 = 'ireg_2'
spiller_1 = 'ireg_3'
spiller_2 = 'ireg_4'
self.register_use_table.acquire(spilled_1)
self.register_use_table.acquire(spilled_2)
self.register_use_table.acquire(spiller_1)
self.register_use_table.acquire(spiller_2)
self.assertTrue(
spilled_1 in self.register_use_table.spilled_registers.keys()
and spilled_2 in self.register_use_table.spilled_registers.keys())
result = self.register_use_table.acquire(spilled_2)
expected_result = {
'register':
mips.T0,
'code': [
assembler.SW(
mips.T0,
assembler.offset_label_immediate(SPILL_MEM_LABEL, 8)),
assembler.LW(
mips.T0,
assembler.offset_label_immediate(SPILL_MEM_LABEL, 4))
]
}
self.assertEqual(expected_result, result)
result = self.register_use_table.acquire(spilled_1)
expected_result = {
'register':
mips.T1,
'code': [
assembler.SW(
mips.T1,
assembler.offset_label_immediate(SPILL_MEM_LABEL, 4)),
assembler.LW(
mips.T1,
assembler.offset_label_immediate(SPILL_MEM_LABEL, 0))
]
}
self.assertEqual(expected_result, result)
def test_register_spill(self):
pseudo_registers = [INT_REGISTER_TICKETS.get() for _ in range(0, 3)]
self.register_use_table.acquire(pseudo_registers[0])
self.register_use_table.acquire(pseudo_registers[1])
self.assertSequenceEqual([], self.register_use_table.available_registers, 'the registers should be used up')
expected_result = {'register': mips.T0, 'code': [assembler.SW(mips.T0, assembler.offset_label_immediate(SPILL_MEM_LABEL, 0))]}
result = self.register_use_table.acquire(pseudo_registers[2])
self.assertEqual(expected_result, result)
def test_spill_recovery(self):
pseudo_registers = [INT_REGISTER_TICKETS.get() for _ in range(0, 3)]
self.register_use_table.acquire(pseudo_registers[0])
self.register_use_table.acquire(pseudo_registers[1])
self.assertSequenceEqual([],
self.register_use_table.available_registers,
'the registers should be used up')
expected_result = {
'register':
mips.T0,
'code': [
assembler.SW(
mips.T0,
assembler.offset_label_immediate(SPILL_MEM_LABEL, 0))
]
}
result = self.register_use_table.acquire(pseudo_registers[2])
self.assertEqual(expected_result, result)
# recovering a spilled register's value from memory should not only get the register, but also provide the
# mips code that swaps the values for the temporaries using the spill memory
expected_result = {
'register':
mips.T1,
'code': [
assembler.SW(
mips.T1,
assembler.offset_label_immediate(SPILL_MEM_LABEL, 4)),
assembler.LW(
mips.T1,
assembler.offset_label_immediate(SPILL_MEM_LABEL, 0))
]
}
result = self.register_use_table.acquire(pseudo_registers[0])
self.assertEqual(expected_result, result)
def test_multiple_recoveries(self):
spilled_1 = 'ireg_1'
spilled_2 = 'ireg_2'
spiller_1 = 'ireg_3'
spiller_2 = 'ireg_4'
self.register_use_table.acquire(spilled_1)
self.register_use_table.acquire(spilled_2)
self.register_use_table.acquire(spiller_1)
self.register_use_table.acquire(spiller_2)
self.assertTrue(
spilled_1 in self.register_use_table.spilled_registers.keys() and spilled_2 in
self.register_use_table.spilled_registers.keys())
result = self.register_use_table.acquire(spilled_2)
expected_result = {'register': mips.T0, 'code': [assembler.SW(mips.T0, assembler.offset_label_immediate(SPILL_MEM_LABEL, 8)),
assembler.LW(mips.T0, assembler.offset_label_immediate(SPILL_MEM_LABEL, 4))]}
self.assertEqual(expected_result, result)
result = self.register_use_table.acquire(spilled_1)
expected_result = {'register': mips.T1, 'code': [assembler.SW(mips.T1, assembler.offset_label_immediate(SPILL_MEM_LABEL, 4)),
assembler.LW(mips.T1, assembler.offset_label_immediate(SPILL_MEM_LABEL, 0))]}
self.assertEqual(expected_result, result)
def test_register_spill(self):
pseudo_registers = [INT_REGISTER_TICKETS.get() for _ in range(0, 3)]
self.register_use_table.acquire(pseudo_registers[0])
self.register_use_table.acquire(pseudo_registers[1])
self.assertSequenceEqual([],
self.register_use_table.available_registers,
'the registers should be used up')
expected_result = {
'register':
mips.T0,
'code': [
assembler.SW(
mips.T0,
assembler.offset_label_immediate(SPILL_MEM_LABEL, 0))
]
}
result = self.register_use_table.acquire(pseudo_registers[2])
self.assertEqual(expected_result, result)
__restore_register_macro_instructions = [mi.COMMENT("brace yourself for a long, unrolled loop...")]
for __temp_register in reversed(__T_REGISTERS):
__restore_register_macro_instructions.append(mi.ADDIU(mr.SP, mr.SP, mr.WORD_SIZE))
__restore_register_macro_instructions.append(mi.LW(__temp_register, mi.offset_from_register_with_immediate(mr.SP)))
if config.NOT_TESTING_FUNCTIONS:
__restore_register_macro_instructions = []
RESTORE_REGISTER_MACRO = Macro(name='RESTORE_T_REGISTERS', args=None, body=__restore_register_macro_instructions)
__save_spill_mem_macro_body = [mi.COMMENT("brace yourself for a long, unrolled loop...")]
for i in range(0, config.SPILL_MEM_SIZE, mr.WORD_SIZE):
__save_spill_mem_macro_body.extend([
mi.LW(mr.A3, mi.offset_label_immediate('SPILL_MEMORY', i)),
mi.SW(mr.A3, mi.offset_from_register_with_immediate(mr.SP)),
mi.SUBIU(mr.SP, mr.SP, mr.WORD_SIZE)
])
if config.NOT_TESTING_FUNCTIONS:
__save_spill_mem_macro_body = []
SAVE_SPILL_MEM_MACRO = Macro(name='SAVE_SPILL_MEM', args=None, body=__save_spill_mem_macro_body)
__restore_spill_mem_macro_body = [mi.COMMENT("brace yourself for a long, unrolled loop...")]
for i in range(config.SPILL_MEM_SIZE - mr.WORD_SIZE, -mr.WORD_SIZE, -mr.WORD_SIZE):
__restore_spill_mem_macro_body.extend([
mi.ADDIU(mr.SP, mr.SP, mr.WORD_SIZE),
mi.LW(mr.A3, mi.offset_from_register_with_immediate(mr.SP)),
mi.SW(mr.A3, mi.offset_label_immediate('SPILL_MEMORY', i))
])
__restore_register_macro_instructions.append(
mi.ADDIU(mr.SP, mr.SP, mr.WORD_SIZE))
__restore_register_macro_instructions.append(
mi.LW(__temp_register, mi.offset_from_register_with_immediate(mr.SP)))
if config.NOT_TESTING_FUNCTIONS:
__restore_register_macro_instructions = []
RESTORE_REGISTER_MACRO = Macro(name='RESTORE_T_REGISTERS',
args=None,
body=__restore_register_macro_instructions)
__save_spill_mem_macro_body = [
mi.COMMENT("brace yourself for a long, unrolled loop...")
]
for i in range(0, config.SPILL_MEM_SIZE, mr.WORD_SIZE):
__save_spill_mem_macro_body.extend([
mi.LW(mr.A3, mi.offset_label_immediate('SPILL_MEMORY', i)),
mi.SW(mr.A3, mi.offset_from_register_with_immediate(mr.SP)),
mi.SUBIU(mr.SP, mr.SP, mr.WORD_SIZE)
])
if config.NOT_TESTING_FUNCTIONS:
__save_spill_mem_macro_body = []
SAVE_SPILL_MEM_MACRO = Macro(name='SAVE_SPILL_MEM',
args=None,
body=__save_spill_mem_macro_body)
__restore_spill_mem_macro_body = [
mi.COMMENT("brace yourself for a long, unrolled loop...")
]
for i in range(config.SPILL_MEM_SIZE - mr.WORD_SIZE, -mr.WORD_SIZE,
-mr.WORD_SIZE):
__restore_spill_mem_macro_body.extend([