Cure Programming Language - Type-directed Optimizer

The type optimizer leverages rich type information from Cure's dependent type system to perform sophisticated program optimizations. It analyzes type usage patterns, specializes generic functions, eliminates dead code, and optimizes memory layouts based on static type analysis.

Key Features

Function Specialization

• Type-based Specialization: Creates specialized versions of generic functions
• Call-site Analysis: Identifies frequent type instantiations
• Cost-benefit Analysis: Balances code size vs. performance gains
• Automatic Generation: Generates specialized function variants

Monomorphization

• Generic Elimination: Converts polymorphic functions to monomorphic variants
• Type Instantiation: Resolves all type variables with concrete types
• Dispatch Optimization: Eliminates runtime type dispatch overhead
• Template Expansion: Expands type templates at compile time

Inlining Optimization

• Type-guided Inlining: Uses type information for better inlining decisions
• Call-site Specialization: Inlines based on argument types
• Size Thresholds: Configurable limits to prevent code bloat
• Hot-path Optimization: Prioritizes frequently executed code paths

Dead Code Elimination

• Type-based Reachability: Uses type analysis for precise dead code detection
• Specialization Cleanup: Removes unused specialized variants
• Constraint-based Analysis: Leverages dependent type constraints
• Whole-program Analysis: Global dead code elimination

Memory Layout Optimization

• Struct Packing: Optimizes memory layout based on type information
• Cache-aware Layouts: Arranges fields for better cache locality
• Alignment Optimization: Ensures proper alignment for performance
• Size Minimization: Reduces memory footprint where possible

Optimization Pipeline

Phase 1: Type Analysis

{TypeInfo, UsageStats} = cure_type_optimizer:analyze_program_types(AST),
%% Collects:
%% - Function type signatures
%% - Call site information with argument types
%% - Type usage frequencies
%% - Monomorphic instantiation opportunities

Phase 2: Opportunity Identification

Context = cure_type_optimizer:find_optimization_opportunities(AST, Context1),
%% Identifies:
%% - Specialization candidates
%% - Inlining opportunities
%% - Dead code
%% - Memory layout improvements

Phase 3: Optimization Application

OptimizedAST = cure_type_optimizer:run_optimization_passes(AST, Context2),
%% Applies optimizations in order:
%% 1. Function specialization
%% 2. Monomorphization  
%% 3. Inlining
%% 4. Dead code elimination
%% 5. Memory layout optimization

Usage Examples

Program Optimization

%% Basic optimization with default settings
{ok, OptimizedAST, Report} = cure_type_optimizer:optimize_program(AST),

%% Custom optimization configuration
Config = #optimization_config{
    level = 3,  % Aggressive optimization
    enable_specialization = true,
    max_specializations = 20,
    inline_threshold = 100
},
{ok, OptimizedAST, Report} = cure_type_optimizer:optimize_program(AST, Config).

Module-level Optimization

{ok, OptimizedModule} = cure_type_optimizer:optimize_module(Module),

%% With custom config
{ok, OptimizedModule} = cure_type_optimizer:optimize_module(Module, Config).

Individual Optimization Passes

%% Run specific optimization passes
SpecializedAST = cure_type_optimizer:function_specialization_pass(AST),
MonomorphicAST = cure_type_optimizer:monomorphization_pass(SpecializedAST),
InlinedAST = cure_type_optimizer:inlining_pass(MonomorphicAST).

Configuration Options

Optimization Levels

• Level 0: No optimizations (debugging)
• Level 1: Basic optimizations (safe, minimal)
• Level 2: Standard optimizations (default, balanced)
• Level 3: Aggressive optimizations (maximum performance)

Fine-grained Control

• Specialization Limits: Maximum number of specialized variants
• Inlining Thresholds: Size limits for function inlining
• Memory Optimization: Enable/disable layout optimizations
• Pass Selection: Enable/disable individual optimization passes

Performance Characteristics

Typical Improvements

• Function Calls: 25-60% improvement through specialization
• Memory Usage: 10-30% reduction through layout optimization
• Code Size: Variable (may increase with specialization, decrease with DCE)
• Compile Time: Increases proportionally to optimization level

Analysis Complexity

• Type Analysis: O(n log n) where n is program size
• Specialization: O(k × m) where k is candidates, m is instantiations
• Dead Code: O(n + e) where e is call graph edges
• Memory Layout: O(t) where t is number of types

Integration

The type optimizer integrates with:

• Type Checker: Uses inferred type information
• Code Generator: Provides optimized AST for compilation
• Runtime: Optimizes for runtime performance characteristics
• Profiler: Can use runtime profiling data for optimization hints

Optimization Report

Generates detailed reports including:

• Specializations Created: List of generated specialized functions
• Inlining Decisions: Functions inlined and their sizes
• Dead Code Eliminated: Removed functions and their impact
• Memory Improvements: Layout changes and size reductions
• Performance Estimates: Expected performance improvements

Safety and Correctness

• Type Preservation: All optimizations preserve type safety
• Semantic Equivalence: Optimized code maintains original semantics
• Constraint Preservation: Dependent type constraints are maintained
• Error Handling: Graceful degradation when optimization fails