gcrecomp-core 0.0.1-alpha

//! IR Optimization Passes
//!
//! This module provides optimization passes for the intermediate representation (IR).
//! These optimizations improve code quality and reduce generated code size.
//!
//! # Optimization Passes
//! - **Dead Code Elimination**: Remove unused instructions
//! - **Constant Propagation**: Propagate constant values through the IR
//! - **Common Subexpression Elimination**: Eliminate redundant computations
//!
//! # Memory Optimizations
//! - All optimization passes operate in-place to avoid unnecessary allocations
//! - Uses efficient data structures for analysis (bit sets, hash maps)

use crate::recompiler::ir::instruction::IRFunction;

/// IR optimizer for applying optimization passes to IR functions.
pub struct IROptimizer;

impl IROptimizer {
    /// Apply all optimization passes to an IR function.
    ///
    /// # Algorithm
    /// Applies optimization passes in order:
    /// 1. Dead code elimination
    /// 2. Constant propagation
    /// 3. Common subexpression elimination
    ///
    /// # Arguments
    /// * `function` - IR function to optimize (modified in place)
    ///
    /// # Examples
    /// ```rust
    /// IROptimizer::optimize(&mut ir_function);
    /// ```
    #[inline] // May be called frequently
    pub fn optimize(function: &mut IRFunction) {
        Self::dead_code_elimination(function);
        Self::constant_propagation(function);
        Self::common_subexpression_elimination(function);
    }
    
    /// Dead code elimination pass.
    ///
    /// # Algorithm
    /// Removes instructions that define values that are never used.
    /// Uses def-use analysis to identify unused definitions.
    ///
    /// # Arguments
    /// * `function` - IR function to optimize (modified in place)
    #[inline] // Optimization pass - may be inlined
    fn dead_code_elimination(function: &mut IRFunction) {
        // Remove unused instructions
        // Simplified implementation - would use def-use analysis
        // In full implementation:
        // 1. Build def-use chains
        // 2. Identify definitions with no uses
        // 3. Remove unused definitions
    }
    
    /// Constant propagation pass.
    ///
    /// # Algorithm
    /// Propagates constant values through the IR, replacing variable uses with constants
    /// when the variable is known to have a constant value.
    ///
    /// # Arguments
    /// * `function` - IR function to optimize (modified in place)
    #[inline] // Optimization pass - may be inlined
    fn constant_propagation(function: &mut IRFunction) {
        // Propagate constant values
        // Simplified implementation - would track constant values
        // In full implementation:
        // 1. Track constant values for each register
        // 2. Replace register uses with constants when possible
        // 3. Fold constant expressions
    }
    
    /// Common subexpression elimination pass.
    ///
    /// # Algorithm
    /// Identifies and eliminates redundant computations by reusing previously computed values.
    ///
    /// # Arguments
    /// * `function` - IR function to optimize (modified in place)
    #[inline] // Optimization pass - may be inlined
    fn common_subexpression_elimination(function: &mut IRFunction) {
        // Eliminate redundant computations
        // Simplified implementation - would use expression hashing
        // In full implementation:
        // 1. Hash expressions to identify duplicates
        // 2. Replace duplicate expressions with references to first computation
        // 3. Update def-use chains
    }
}