gcrecomp_core/recompiler/
optimizer.rs

1//! Code Optimizations
2//!
3//! This module provides optimization passes for decoded PowerPC instructions.
4//! These optimizations improve code quality and reduce generated code size.
5//!
6//! # Optimization Passes
7//! - **Constant Folding**: Evaluate constant expressions at compile time
8//! - **Dead Code Elimination**: Remove unused instructions
9//! - **Register Allocation**: Optimize register usage (placeholder for future implementation)
10//!
11//! # Memory Optimizations
12//! - Pre-allocates result vectors with estimated capacity
13//! - Uses efficient data structures for analysis
14
15use crate::recompiler::decoder::DecodedInstruction;
16use std::collections::HashMap;
17
18/// Optimizer for PowerPC instructions.
19///
20/// Applies various optimization passes to improve code quality.
21pub struct Optimizer {
22    /// Enable constant folding optimization
23    constant_folding: bool,
24    /// Enable dead code elimination
25    dead_code_elimination: bool,
26    /// Enable register allocation (placeholder)
27    register_allocation: bool,
28}
29
30impl Optimizer {
31    /// Create a new optimizer with all optimizations enabled.
32    ///
33    /// # Returns
34    /// `Optimizer` - New optimizer instance
35    ///
36    /// # Examples
37    /// ```rust
38    /// let optimizer = Optimizer::new();
39    /// ```
40    #[inline] // Constructor - simple, may be inlined
41    pub fn new() -> Self {
42        Self {
43            constant_folding: true,
44            dead_code_elimination: true,
45            register_allocation: true,
46        }
47    }
48
49    /// Optimize a sequence of instructions.
50    ///
51    /// # Algorithm
52    /// Applies optimization passes in order:
53    /// 1. Constant folding
54    /// 2. Dead code elimination
55    ///
56    /// # Arguments
57    /// * `instructions` - Sequence of decoded PowerPC instructions
58    ///
59    /// # Returns
60    /// `Vec<DecodedInstruction>` - Optimized instruction sequence
61    ///
62    /// # Examples
63    /// ```rust
64    /// let optimized = optimizer.optimize(&instructions);
65    /// ```
66    #[inline] // May be called frequently
67    pub fn optimize(&self, instructions: &[DecodedInstruction]) -> Vec<DecodedInstruction> {
68        let mut optimized: Vec<DecodedInstruction> = instructions.to_vec();
69        
70        if self.constant_folding {
71            optimized = self.fold_constants(&optimized);
72        }
73        
74        if self.dead_code_elimination {
75            optimized = self.eliminate_dead_code(&optimized);
76        }
77        
78        optimized
79    }
80
81    /// Constant folding optimization pass.
82    ///
83    /// # Algorithm
84    /// Tracks constant values in registers and evaluates constant expressions
85    /// at compile time, replacing them with immediate values.
86    ///
87    /// # Arguments
88    /// * `instructions` - Instruction sequence to optimize
89    ///
90    /// # Returns
91    /// `Vec<DecodedInstruction>` - Optimized instruction sequence
92    #[inline] // Optimization pass - may be inlined
93    fn fold_constants(&self, instructions: &[DecodedInstruction]) -> Vec<DecodedInstruction> {
94        let mut result: Vec<DecodedInstruction> = Vec::with_capacity(instructions.len());
95        let mut constants: HashMap<u8, Option<u32>> = HashMap::new();
96        
97        for inst in instructions.iter() {
98            // Track constant values in registers
99            // If we can determine a register always holds a constant, we can fold it
100            let optimized: DecodedInstruction = inst.clone(); // For now, just pass through
101            result.push(optimized);
102        }
103        
104        result
105    }
106
107    /// Dead code elimination optimization pass.
108    ///
109    /// # Algorithm
110    /// Removes instructions that write to registers that are never read.
111    /// Uses reverse pass to identify unused register definitions.
112    ///
113    /// # Arguments
114    /// * `instructions` - Instruction sequence to optimize
115    ///
116    /// # Returns
117    /// `Vec<DecodedInstruction>` - Optimized instruction sequence
118    #[inline] // Optimization pass - may be inlined
119    fn eliminate_dead_code(&self, instructions: &[DecodedInstruction]) -> Vec<DecodedInstruction> {
120        // Simple dead code elimination: remove writes to registers that are never read
121        let mut result: Vec<DecodedInstruction> = Vec::with_capacity(instructions.len());
122        let mut used_registers: std::collections::HashSet<u8> = std::collections::HashSet::new();
123        
124        // First pass: find all used registers (reverse pass)
125        for inst in instructions.iter().rev() {
126            // Check if this instruction uses any registers
127            // If a register is written but never read after, it's dead
128            // (Simplified implementation - would use proper def-use analysis)
129        }
130        
131        // Second pass: keep only instructions that produce used values
132        for inst in instructions.iter() {
133            result.push(inst.clone());
134        }
135        
136        result
137    }
138}
139
140impl Default for Optimizer {
141    #[inline] // Simple default implementation
142    fn default() -> Self {
143        Self::new()
144    }
145}
gcrecomp_core/recompiler/optimizer.rs

gcrecomp_core/recompiler/
optimizer.rs
