The Scala Compiler Corner:     A collection of resources for compiler hackers Companion websites: All about the Scala.NET compiler The jdk2ikvm automatic migration tool

Code walkthroughs of the compiler

• First-half of the pipeline: parser, namer, packageobjects, typer, superaccessors, pickler, refchecks, liftcode, uncurry, tailcalls, specialize
• Second-half of the pipeline: explicitouter, AddInterfaces, erasure, lazyvals, lambdalift, constructors, flatten, mixin, cleanup
• ICode and its optimizers: GenICode, inliner, inlineExceptionHandlers, closelim, dce
• Backends: GenASM, GenJVM, GenMSIL.

The scalac optimizer

• A new backend and optimizer for scalac (February 2014)
• Parallelization of optimization phases (January 2012)

Compiler plugins

• Experimental optimizations
  • Transforming Function nodes (standing for closures) before uncurry turns them into anonymous classes (November 2011)
  • Partial evaluation based on three-address-form, including conversion back to stack-based language (November 2011)
  • Moving Scala ASTs one step closer to C, by turning them into three-address form (a Jimple-like IR) (September 2011)
  
  
• Miscellaneous AST transformation
  • Work in progress: GOTO elimination in Scala ASTs (February 2011)
  • Work in progress: What about an explicit formulation of module initialization as ICode-level desugarings (May 2010)
  
  
• Source-level, AST-backed transformations that preserve layout
  • Finding the source code fragment that corresponds to a given AST-level type-reference (January 2011)
  • A source-level, automatic API migration that preserves layout (a story of range positions) (January 2011)
  
  
• Unparsing
  • Work in progress: Unparsing types the Scaladoc way (January 2011)
  • Bits and pieces of information about the parser, namer, and typer phases that turn out to be necessary just to be able to unparse Scala ASTs (December 2010)
  • Learning and doing scalac transformations the easy way: via unparsing (December 2010)

ICode transformation

• Dataflow Analyses on ICode (November 2011)
• Using reaching-defs and type-flow analyses to turn ICode into a stackless IR (April 2010). Prototypes: first, second
• SSA, as part of Scala on LLVM by Geoff Reedy

Exploring invokedynamic and MethodHandle

• Runtime metaprogramming via java.lang.invoke.MethodHandle (May 2012)

Related resources

• Talks
• 2013-04-11: The backend that makes scalac faster for real
• 2012-11-04: Faster closures in Scala via Stack-allocation
• 2012-07-03: GC-savvy Closure conversion
• 2012-05-01: Functionality ready to land in optimizer and backend
• 2012-04-18: What the optimizer does to your code (slides, video) at Scala Days 2012
• 2011-11-22: Just trying to generate faster code faster under -optimise
• 2011-02-22: A few additional AST lowerings that can simplify the development of new backends (LaTeX sources)
• 2011-01-18: jdk2ikvm and scala.tools.unparse
• Reflection Guide, Macros Guide
• Kiama, a DSL and library for language processing, http://code.google.com/p/kiama/
• Report by Mirko Stocker on the Scala Refactoring Project, http://scala.ifs.hsr.ch/
• Project ideas
• Emitting Android .dex classes directly. A report on Dalvik bytecode semantics.