Programming Language Interpreter Design MIPS

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apply your understanding of MIPS assembly language to implement a program that simulates a simple esoteric language interpreter, specifically for a language called “Brainfry.” This task will test your ability to work with memory manipulation, loops, and conditional branches in MIPS.

Description:

Brainfry is an esoteric programming language that operates on a virtual “tape” consisting of memory cells, where each cell can hold a single byte. The tape is manipulated by moving a “tape head” (a pointer to the current memory cell) left or right, and by incrementing or decrementing the value at the current memory cell.

You will implement a MIPS program that reads a series of Brainfry commands and executes them on a simulated tape of 5,000 memory cells. The following Brainfry commands must be supported in your MIPS implementation:

>: Move the tape head to the right.
<: Move the tape head to the left.
+: Increment the value of the current memory cell.
-: Decrement the value of the current memory cell.
.: Output the value of the current memory cell as an ASCII character.
,: Input a value from the user and store it in the current memory cell.
[: If the value of the current memory cell is 0, jump to the corresponding ] command.
]: If the value of the current memory cell is not 0, jump to the corresponding [ command.
All other characters should be ignored by your MIPS program. The end of the program is signified by a ~ character, after which the input to the Brainfry program follows.

 

Sample Solution

Understanding Brainfry and MIPS

  • Brainfry: A simple esoteric language operating on a tape of memory cells, using commands to move the tape head, modify cell values, and input/output.
  • MIPS: A RISC architecture assembly language with a rich instruction set for memory manipulation, conditional branches, and arithmetic operations.

MIPS Implementation Outline

  1. Memory Initialization: Allocate a 5,000-byte array to simulate the Brainfry tape.
  2. Tape Head Pointer: Initialize a register to point to the current memory cell on the tape.
  3. Command Loop:
    • Read a character from the input.
    • Based on the character, execute the corresponding Brainfry command:
      • >: Increment the tape head pointer.
      • <: Decrement the tape head pointer.
      • +: Increment the value at the current memory cell.
      • -: Decrement the value at the current memory cell.
      • .: Print the ASCII character corresponding to the current cell value.
      • ,: Read a character from the user and store its ASCII value in the current cell.
      • [: If the current cell value is 0, jump to the matching ].
      • ]: If the current cell value is not 0, jump to the matching [.
    • Continue reading and executing commands until a ~ is encountered.

MIPS Code Example

MIPS Assembler
# Initialize the tape and tape head pointer
.data
tape: .space 5000
tape_head: .word 0

.text
.globl main
main:
    # Load the address of the tape into a register
    la $t0, tape

    # Initialize the tape head pointer
    li $t1, 0

    # Read commands and execute them
read_loop:
    lb $t2, 0($a0)
    beq $t2, '~', end_program

    # Implement the Brainfry commands here
    # For example:
    beq $t2, '>', move_right
    beq $t2, '<', move_left
    # ...

    # Continue reading commands
    addi $a0, $a0, 1
    j read_loop

end_program:
    # End the program
    li $v0, 10
    syscall

Key Considerations

  • Memory Bounds Checking: Ensure that the tape head pointer doesn’t go beyond the allocated memory.
  • Nested Loops: Implement a stack-based approach to handle nested [ ] loops.
  • Error Handling: Consider handling potential errors like invalid commands or memory access violations.
  • Efficiency: Optimize your code for performance, especially for large inputs.

By following this outline and addressing these considerations, you can create a functional Brainfry interpreter in MIPS assembly.

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