# Simple English | [日本語](README.ja.md) A Simple showcase for the Sea-of-Nodes compiler IR This repo is intended to demonstrate the Sea-of-Nodes compiler IR. The Sea-of-Nodes is the core IR inside of HotSpot's C2 compiler and Google's V8 compiler and Sun/Oracle's Graal compiler. Since we are showcasing the SoN IR, the *language* being implemented is less important. We're using a very simple language similar to C or Java, but with far fewer features. Simple is strongly typed, object-oriented, with first-class *functions* not *closures*. Object references are pointers, and null pointer exceptions are disallowed by the typing system. Arrays will probably be range-checked at some point, making Simple a fully safe language. Simple has a minimal syntax that can be parsed with a recursive descent parser. The Sea-of-Nodes is used for machine code generation in these industrial strength systems - but for this demonstration the backend is both difficult and less important. This repo targets x86-64, RISC-V and ARM64 with ahead-of-time compilation - but with an eye towards JIT compilation. This repo also is not intended to be a complete language in any sense, and so the backend starts with a Java evaluator (first introduced in Chapter 8) that directly interprets the SoN IR. Code generation first appears in Chapter 19. ## Chapters The following is a rough plan, subject to change. Each chapter will be self-sufficient and complete; in the sense that each chapter will fully implement a subset of the Simple language, and include everything that was created in the previous chapter. Each chapter will also include a detailed commentary on relevant aspects of the Sea Of Nodes intermediate representation. The Simple language is styled after a subset of C or Java. * [Chapter 1](docs/chapter01/README.md): Script that returns an integer literal, i.e., an empty function that takes no arguments and returns a single integer value. The `return` statement. * [Chapter 2](docs/chapter02/README.md): Simple binary arithmetic such as addition, subtraction, multiplication, division with constants. Peephole optimization / simple constant folding. * [Chapter 3](docs/chapter03/README.md): Local variables, and assignment statements. Read on RHS, SSA, more peephole optimization if local is a constant. * [Chapter 4](docs/chapter04/README.md): A non-constant external variable input named `arg`. Binary and Comparison operators involving constants and `arg`. Non-zero values will be truthy. Peephole optimizations involving algebraic simplifications. * [Chapter 5](docs/chapter05/README.md): `if` statement. CFG construction. * [Chapter 6](docs/chapter06/README.md): Peephole optimization around dead control flow. * [Chapter 7](docs/chapter07/README.md): `while` statement; looping constructs - eager phi approach. * Chapter 8: Looping constructs continued, lazy phi creation, `break` and `continue` statements. * Chapter 9: Global Value Numbering. Iterative peepholes to fixpoint. Worklists. * Chapter 10: User defined structs, pointers and null analysis. One memory value in SSA. Loads, stores, and an executable evaluator. * Chapter 11: Equivalence class aliasing. Lazy memory partitioning with `MemMerge`, `MemPhi`, and `BulkMemPhi`. * Chapter 12: Reference fields, forward references and recursive structs. * Chapter 13: Global Code Motion - Scheduling. * Chapter 14: Numeric types: floats, narrow integers, ranges and rounding to `f32`. * Chapter 15: One dimensional static length array type, with array loads and stores. * Chapter 16: Constructors * Chapter 17a: Binding mutability, reference permissions, and deep read-only views. * Chapter 17b: Syntax sugar: `var`, `val`, `x+=y`, `for(init; test; next) body` * Chapter 18: Functions and calls. * Chapter 19: Instruction selection and portable compilation * Chapter 20: Graph Coloring Register Allocation * Chapter 21: Instruction Encodings & ELF * Chapter 22: A Simple Hello, World! * Chapter 23: Methods and Types Revisited * Chapter 24a: SCCP Within a Function * Chapter 24b: SCCP Across Functions * Chapter 25: SSA Before Types Are Known * Chapter 26: Construction and Private Memory * Chapter 27: Escape Analysis and Unknown Callers * Chapter 28a: Modules and Lazy Class Initialization * Chapter 28b: Separate Compilation Appendices: [Native libraries](docs/appendices/native-libraries.md), [optimizer and backend tuning](docs/appendices/optimizer-tuning.md). Future compiler and language work is collected in the [roadmap](docs/roadmap.md). ## Building across chapters The optional [interactive graph viewer](graph/README.md) is shared in `graph/`. All chapters launch it with `make view` from the chapter directory. The [debug printers](print/README.md) are shared in `print/`; Chapter 2 needs only a one-line expression format. A shared `BaseNode` supplies identity and edge access to both printers and the viewer; chapter adapters add semantic details as the IR grows. The [instruction encoders](isa/README.md) share x86-64, ARM, and RISC-V byte emission for Chapters 21–28b, along with ARM/RISC-V test evaluators. Machine-node selection, register allocation, and code layout remain in each chapter; the shared layer takes concrete operands and writes bytes. The top-level Makefile runs each chapter's `tests`, `tags` (also `tag`), `release`, or `lib` target. Start with `make lib` on a fresh checkout, then `make tests`. CI runs `make lib tests CTAGS=` on Linux with JDK 21. The Make targets also build Chapter 28b's native runtime and `sys` library before running the tests that use them; Maven's Java build alone does not produce those prerequisites. Chapters 10-14 cover whole memory, lazy alias splitting, references, GCM, and numeric types in that order. Later chapters build on this memory representation. To build and test just the memory chapters: ```sh make lib tests release CHAPTERS="chapter10 chapter11 chapter12" ``` Every chapter has an IntelliJ module with its own compiler and test classpath. See [the IntelliJ setup](docs/intellij.md) to open and debug any chapter's tests. The root Maven reactor also includes every chapter. Make and the linear-history workflow discover the numbered chapter directories.