Add Phi-Nodes to Your SSA IR

Your Task

Implement phi-node insertion and handling in your SSA IR.

Requirements

1. Extend IR instruction set:

   • Add OP_PHI operation type
   • Phi instruction format: result = φ(arg1, arg2, ..., argN)

2. Phi-node placement algorithm:

   • Compute dominance frontier for each basic block
   • Insert phi-nodes at join points where variables merge
   • Handle multiple variables and multiple predecessors

3. Phi-node execution:

   • Select correct operand based on incoming edge
   • Track which predecessor we came from
   • Update variable versions after phi

4. Test scenarios:

   • If-else statements
   • Loops (while/for)
   • Nested control flow
   • Multiple variable merges

Success Criteria

• Correctly identify join points needing phi-nodes
• Insert phi-nodes for all variables that merge
• Handle nested control flow correctly
• Phi-nodes select correct value at runtime