Compiler Project Decaf

Komphyler

HamidReza Kamkari   97110177

Mostafa Ojaghi      97105782

Yeganeh Gharedaghi  97106216

TAC format

Input and Output: The following commands handle simple input and output of character.

• Input x: Takes an Integer as an input and writes it in x
• Output x: Outputs the value in x.

Assign value commands:

• Assign x = y: Set the value of x equal to the value of y
• Assign x = a op b: This command calculates a op b and then writes the output in x. op can have forms such as follows:
  • +: Add a and b
  • -: Subtract b from a
  • *: Multiply a and b
  • /: Calculate a divided by b
  • %: Calculate a mod b
  • <: If a is strictly less than b then the value 1 will be written into x otherwise 0
  • <=: If a is less than or equal to b then the value 1 will be written into x otherwise 0
  • >: If a is strictly larger than b then the value 1 will be written into x otherwise 0
  • >=: If a is larger than or equal to b then the value 1 will be written into x otherwise 0
  • ==: If a and b are equal then 1 will be written into x otherwise 0
  • !=: If a and b are not equal then 1 will be written into x otherwise 0
  • &&: Calculate logical and of a and b (a and b should be 0 or 1)
  • ||: Calculate logical or of a and b (a and b should be 0 or 1)
• Assign x = not y: y should be 0 or 1 and the calculated not is written into x
• Assign x = - y: negate y and then write the negated value into x

Labels and goto:

• label labelName:: defines a label to be able to jump to.
• goto labelName: A simple jump to label named labelName

Function call commands:

• label functionName: param1 param2 param3 ...: This defines a label, if the label is a function the parameters param1, param2, ... are the input arguments.
• Lcall functionName: Call the function that has a label named functionName
• Lcall functionName -> r: Call the function that has a label named functionName and then return the value from that function in r
• Pushparam x: This adds argument x to the stack before function call.
• Popparams sz: Free the stack
• Beginfunc sz: Free the stack by sz bytes, this is used to free space for each local variable that is used in the function. Caution: keep in mind if you have 3 variables in a function you should start the function with Beginfunc 12.
• Endfunc: ends the function.
• Endfunc var: returns the value that is stored in var

Exit command:

• Exit: If this line is read then the program exits.

Global Variables: each program in TAC is written as follows:

Assign g1 = 0
Assign g2 = 0
Assign g3 = 0
.
.
.
Assign gk = 0
Lcall main
Exit

label main:
Beginfunc s
.
.
.
Endfunc

label func1: arg1 arg2 ...
Beginfunc s1
.
.
.
Endfunc ret1/nothing

label func2: arg1 arg2 ...
.
.
.

The variables g1, g2, ..., gk are all global variables and the function main is the function that is being called. Other procedures such as func1, func2 ... are all functions that may or may not return value. To call each of these functions an arbitrary amount of Pushparam x may be needed if they have input arguments and then after each function call there should be a Popparams sz.

Pointers: The following commands include memory access.

• Store *(a + offset) = b: Store the value of b in offset bytes after a in memory.
• Load a = *(b + offset): Load the value in addes b + offset of memory

##TAC tests

Simple function call example:

Assign global1 = 10
Assign global2 = 20
Lcall main
Exit

label main:
Assign x = 0
Assign y = 1
Assign z = 2
Pushparam x
Pushparam y
Pushparam z
Lcall function -> r
Popparams 12

label function: z y x
Beginfunc 4
Assign s = x + y
Assign s = s - z
Assign s = s + global1
Endfunc s

Lcall main
Exit

Label main:
Beginfunc 64
Input s
Output s
Input a
Output a
Assign b = s / a
Assign b = - s
Output b
Pushparam b
Lcall f -> x
Popparams 4
Output x
Endfunc

Label f: c
Beginfunc 64
Output c
Lcall check
Endfunc c

Label check:
Beginfunc 64
Input y
Output y
Endfunc