Implementing a Mid-Level Intermediate Representation (MIR) in Rust

This challenge asks you to design and implement a simplified Mid-Level Intermediate Representation (MIR) for a subset of a programming language in Rust. MIRs are crucial in compilers as they bridge the gap between high-level source code and low-level machine code, facilitating various optimizations and analyses. Successfully building this MIR will deepen your understanding of compiler design principles and Rust's expressive power for such tasks.

Problem Description

Your task is to create a Rust data structure that represents a Mid-Level Intermediate Representation. This MIR should be capable of representing basic arithmetic operations, variable assignments, and conditional branching. You will define the fundamental building blocks of this MIR and provide a way to construct it from a conceptual source.

Key Requirements:

• Instruction Set: Define a set of instructions that can represent:
  • Loading and storing variables.
  • Arithmetic operations (addition, subtraction, multiplication, division).
  • Comparisons (equality, less than, greater than).
  • Conditional branching (jump if true, jump if false).
  • Unconditional jumps.
  • No-operation (nop) for potential placeholder use.
• Data Representation: Decide how to represent values, variables, and labels (for jumps) within your MIR. Consider using enums for instructions and potentially distinct types for operands.
• Structure: The MIR should be a sequence of instructions, possibly grouped into basic blocks (though for this challenge, a simple linear sequence is acceptable, with labels handling control flow).
• Constructibility: While you won't be parsing actual source code, imagine a scenario where you'd construct this MIR. Your implementation should make it relatively straightforward to create MIR instances programmatically.

Expected Behavior:

Your implementation should result in a Rust struct or enum that accurately models the defined instructions and their operands. You should be able to create instances of this MIR and inspect their structure.

Edge Cases:

• Division by zero (how would your MIR represent or handle this, if at all – for this challenge, assume valid inputs or represent it conceptually).
• Unreachable code (your structure should be able to represent sequences that might contain unreachable instructions).
• Complex operand combinations (e.g., an operation whose operand is another operation's result – for simplicity, assume operands are primarily variables, constants, or labels).

Examples

Example 1: Simple Assignment and Addition

Input Concept:
let x = 10;
let y = x + 5;

Conceptual MIR Representation:

block_0:
  assign_const %v0, 10
  load_var %t1, x
  add %t2, %t1, %v0
  store_var %t2, y

Explanation:
The input code is translated into a sequence of MIR instructions.
- `assign_const %v0, 10`: Assigns the constant value 10 to a temporary variable `%v0`.
- `load_var %t1, x`: Loads the value of variable `x` into temporary variable `%t1`.
- `add %t2, %t1, %v0`: Adds the values in `%t1` and `%v0` and stores the result in temporary variable `%t2`.
- `store_var %t2, y`: Stores the result from `%t2` into variable `y`.
(Note: In a real compiler, temporaries would be managed more formally. For this challenge, you can use simple identifiers or rely on instruction ordering.)

Example 2: Conditional Branch

Input Concept:
if (a > b) {
  x = 1;
} else {
  x = 0;
}

Conceptual MIR Representation:

block_0:
  load_var %t1, a
  load_var %t2, b
  cmp_gt %t3, %t1, %t2  // Compare a > b, result in %t3
  jump_if_false %t3, label_else
  // Code for the 'if' block
  assign_const %v1, 1
  store_var %v1, x
  jump label_end // Unconditional jump to skip 'else'
label_else:
  // Code for the 'else' block
  assign_const %v2, 0
  store_var %v2, x
label_end:
  nop // End of the block

Explanation:
- The comparison `a > b` is performed, with the result (boolean) stored in `%t3`.
- `jump_if_false %t3, label_else`: If `%t3` is false, execution jumps to `label_else`.
- If `%t3` is true, the code for the 'if' block executes, setting `x` to 1.
- `jump label_end`: An unconditional jump skips the 'else' block and goes to the end.
- `label_else` marks the beginning of the 'else' block, where `x` is set to 0.
- `label_end` marks the point after the conditional logic.

Constraints

• Your MIR implementation should be entirely within Rust.
• The representation should be clear enough to understand the flow of control and data.
• Performance of constructing the MIR is not a primary concern, but the data structures should be reasonably efficient for typical compiler front-end operations.
• You are not expected to implement any optimization passes or code generation. Focus solely on the MIR data structure and its representation.

Notes

Think about how you would represent operands: constants, variables, temporary values, and labels. Enums are likely to be very useful for defining instructions and operand types. Consider using structs to hold instructions with multiple operands. You might find it helpful to define distinct types for constants, variable names, and labels to ensure type safety. For this exercise, you can assume an infinite supply of temporary registers/values and use simple naming conventions like %t0, %t1, etc., conceptually.