Optimize CodeGen for executable jar

[Thushara-Piyasekara]

Purpose

Depends on #42433 and #42792.

The Ballerina compiler currently includes all imported modules in their entirety within the final executable JAR. However, these modules may contain unused constructs that bloat the final size. This project proposes an optimization to remove these unused parts, resulting in several benefits:

• Smaller final executable JAR: Reduced file size improves storage efficiency and distribution.
• Faster GraalVM native image build: Less code translates to quicker build times.
• Smaller GraalVM native image executable: A more compact native image improves deployment efficiency.
• Potential startup time improvements: A smaller executable might lead to faster program startup.

This project is driven by the substantial benefits it brings to GraalVM native image builds. We've achieved significant improvements in both build time (up to 15.95% faster) and executable size (up to 20.9% smaller). See the attached performance comparison in the Samples section for detailed results.

Approach

We implemented a two-tier Optimization Architecture for this project,

1. Ballerina Codegen Optimization: The Ballerina code generation process is optimized to eliminate unused constructs like functions and type definitions. The current implementation filters the unused constructs after the BIRGen phase.

2. Native Dependency Optimization: During final JAR creation, the final executable JAR is optimized at the bytecode level, currently targeting JVM bytecode classes. This phase optimizes the platform dependency JARs used by ballerina packages.

Further implementation details can be found here.

Samples

Refer to GraalVM native build time and performance comparison for more details.

Remarks

• Only unused functions and type definitions are optimized for ballerina source derived code.
• Bytecode level optimization is done in ".class" file level.

Check List

• Read the Contributing Guide
• Updated Change Log
• Checked Tooling Support (#)
• Added necessary tests
  • Unit Tests
  • Spec Conformance Tests
  • Integration Tests
  • Ballerina By Example Tests
• Increased Test Coverage
• Added necessary documentation
  • API documentation
  • Module documentation in Module.md files
  • Ballerina By Examples

[heshanpadmasiri]

We'll merge this to feature branch and then merge it the master separately