def generate_str_cmp(self):
self.current_procedure = mips.ProcedureNode(STR_CMP)
#comparing char by char
self.register_instruction(mips.CommentNode, "Comparing char by char")
self.register_instruction(mips.LoadWordNode, s0, CHARS_ATTR_OFFSET,
t6) #char array pointer offset
self.register_instruction(mips.LoadWordNode, s1, CHARS_ATTR_OFFSET, t7)
#char by char loop
self.register_instruction(mips.Label, "strcmp_loop")
self.register_instruction(mips.LoadInmediate, s2, 0)
self.register_instruction(mips.LoadByteNode, s2, 0, s0)
self.register_instruction(mips.LoadInmediate, s3, 0)
self.register_instruction(mips.LoadByteNode, s3, 0, s1)
self.register_instruction(mips.SetEq, a0, s2, s3)
self.register_instruction(mips.BranchOnEqZero, a0, "end_loop")
self.register_instruction(mips.BranchOnEqZero, s3, "end_loop")
self.register_instruction(mips.BranchOnEqZero, s2, "end_loop")
self.register_instruction(mips.AddiNode, s0, s0, 1)
self.register_instruction(mips.AddiNode, s1, s1, 1)
self.register_instruction(mips.Jump, "strcmp_loop")
self.register_instruction(mips.Label, "end_loop")
self.register_instruction(mips.JumpRegister, ra)
self.text.append(self.current_procedure)
def generate_input(self):
# copies from t7 to t6 a0 bytes
self.memo.save()
reg4 = self.memo.get_unused_reg()
reg5 = self.memo.get_unused_reg()
self.current_procedure = mips.ProcedureNode("Input")
self.register_instruction(mips.Label, "input_loop")
self.register_instruction(mips.LoadByteNode, t8, 0, t7)
self.register_instruction(mips.StoreByteNode, t8, 0, t6)
self.register_instruction(mips.AddiNode, t6, t6, 1)
self.register_instruction(mips.AddiNode, t7, t7, 1)
self.register_instruction(mips.BranchOnGreaterZero, t8, "input_loop")
self.register_instruction(mips.AddiNode, t6, t6, -2)
self.register_instruction(mips.LoadInmediate, reg4, 10)
self.register_instruction(mips.LoadByteNode, reg5, 0, t6)
self.register_instruction(mips.BranchOnNotEqualNode, reg4, reg5,
"input_end")
self.register_instruction(mips.LoadInmediate, t8, 0)
self.register_instruction(mips.StoreByteNode, t8, 0, t6)
self.register_instruction(mips.Label, "input_end")
self.register_instruction(mips.Jump, ra)
self.text.append(self.current_procedure)
def generate_str_length(self):
# calculates the length of the null-terminated char array referenced by $a0 and stores it in $a0
self.memo.save()
reg1 = self.memo.get_unused_reg()
reg2 = self.memo.get_unused_reg()
self.current_procedure = mips.ProcedureNode(LENGTH)
self.register_instruction(mips.LoadInmediate, reg1, 0)
self.register_instruction(mips.Label, "length_loop")
self.register_instruction(mips.LoadByteNode, reg2, 0, a0)
self.register_instruction(mips.BranchOnEqualNode, zero, reg2,
"length_end")
self.register_instruction(mips.AddiNode, reg1, reg1, 1)
self.register_instruction(mips.AddiNode, a0, a0, 1)
self.register_instruction(mips.Jump, "length_loop")
self.register_instruction(mips.Label, "length_end")
self.register_instruction(mips.MoveNode, a0, reg1)
self.register_instruction(mips.Jump, ra)
self.text.append(self.current_procedure)
self.memo.clean()
def generate_copy(self):
# copies from t1 to t6 a0 bytes
self.memo.save()
self.current_procedure = mips.ProcedureNode(COPY)
self.register_instruction(mips.Label, "copy_loop")
self.register_instruction(mips.BranchOnEqualNode, zero, a0, "copy_end")
self.register_instruction(mips.LoadByteNode, t8, 0, t7)
self.register_instruction(mips.StoreByteNode, t8, 0, t6)
self.register_instruction(mips.AddiNode, t6, t6, 1)
self.register_instruction(mips.AddiNode, t7, t7, 1)
self.register_instruction(mips.AddiNode, a0, a0, -1)
self.register_instruction(mips.Jump, "copy_loop")
self.register_instruction(mips.Label, "copy_end")
self.register_instruction(mips.Jump, ra)
self.text.append(self.current_procedure)
self.memo.clean()
def visit(self, node):
self.memo.save()
locals_save = self.locals
params_save = self.params
self.locals, self.params = [], []
self.current_procedure = mips.ProcedureNode(node.name)
saved_fp = self.memo.get_unused_reg()
self.register_instruction(mips.MoveNode, saved_fp, fp)
self.register_instruction(mips.CommentNode, "New $fp")
self.register_instruction(mips.MoveNode, fp, sp)
self.register_instruction(mips.CommentNode,
"Reserving space for locals")
self.register_instruction(mips.AddiNode, sp, sp,
4 * len(node.localvars))
self.register_instruction(mips.CommentNode, "Pushing $ra")
self.register_push(ra)
self.register_instruction(mips.CommentNode, "Saving $fp")
self.register_push(saved_fp)
self.memo.clean()
for local in node.localvars:
self.locals.append(local.name)
for param in node.params:
self.params.append(param.name)
self.register_instruction(mips.CommentNode, "Executing instructions")
for inst in node.instructions:
self.visit(inst)
self.text.append(self.current_procedure)
self.locals = locals_save
self.params = params_save