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# Simple
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 show casing 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 will eventually target X86 and at least one more
machine with ahead-of-time compilation - but with an eye to JIT compilation.
This repo also is not intended to be a complete language in any sense, and so
the backend starts with levering Java: the Evaluator (first appears in Chapter
10) directly slowly interprets the SoN IR. Code-gen 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 will be 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 construct - eager phi approach.
* [Chapter 8](docs/chapter08/README.md): Looping construct continued, lazy phi creation, `break` and `continue` statements.
* [Chapter 9](docs/chapter09/README.md): Global Value Numbering. Iterative peepholes to fixpoint. Worklists.
* [Chapter 10](docs/chapter10/README.md): User defined Struct types. Memory effects: general memory edges in SSA. Equivalence class aliasing. Null pointer analysis. Peephole optimization around load-after-store/store-after-store.
* [Chapter 11](docs/chapter11/README.md): Global Code Motion - Scheduling.
* [Chapter 12](docs/chapter12/README.md): Float type.
* [Chapter 13](docs/chapter13/README.md): Nested references in Structs.
* [Chapter 14](docs/chapter14/README.md): Narrow primitive types (e.g. bytes)
* [Chapter 15](docs/chapter15/README.md): One dimensional static length array type, with array loads and stores.
* [Chapter 16](docs/chapter16/README.md): Constructors
* [Chapter 17](docs/chapter17/README.md): Mutability & Syntax Sugar: `var`, `val`, `x+=y`, `for(init;test;next)body`
* Chapter 18: Functions and calls.
* Chapter 19: Code gen to X86-64.
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