Deep dive into the Scala Native internals.pptx

A presentation titled "Deep Dive Into the Scala Native Internals" featured during 2021 Scala Love Conference

1. Deep D ive Into the Scala Native Internals

2. What is Scala Native? Part 1

3. Scala JVM

4. What is Scala Native? Created by Denys Shabelin at EPFL Ahead of time compiler Dedicated runtime containing subset of Java standard library. Since 2020 maintained by Scala Center Low-level operations and interop with C Instant startup and targeting high peak performance

5. Brief introduction Part 2

6. Scalac pipeline

7. How its made? Part 2

8. Native Intermediate Representation (NIR) Definitions Low level: Var, Const, Declare, Define High level Class, Trait, Module Types: Primitives, Aggregates - Struct, fixed size Arrays References: Ref, Array, Null, Unit Special types: Function, Var, Varargs, Nothing Values: Low-level Local and Global identifiers Primitive value types Structs and Arrays High-level ClassOf, String, Const, Unit Instructions Label, Let Control Flow - Jump, Call, If, Try, Throw Operands Low-level: Store, Load Call, Stackalloc Add, Comp, Conv High-level: Method, C lassalloc, S izeOf, As, Is, Box, Unbox Attributes Inlining hints Linking informations: link, stu b Extern

9. Native Intermediate Representation (NIR) Single Static Assignment based Strongly typed Supports high-level oriented structures Single top-level scope Globally unique mangled names

10. Name mangling <mangled-name> ::= _S <defn-name> <defn-name> ::= T <name> // top-level name M <name> <sig-name> // member name <sig-name> ::= F <name> <scope> // field name R <type-name>+ E // constructor name D <name> <type-name>+ E <scope> // method name C <name> // c extern name G <name> // generated name … <name> ::= <length number> [-] <chars> <type-name> ::= v // c vararg R _ // c pointer type-name R <type-name>+ E // c function type-name S <type-name>+ E // c anonymous struct type-name A <type-name> <number> _ // c array type-name b // scala.Byte s / / scala.Short i // scala.Int j // scala.Long z // scala.Boolean c // scala.Char f // scala.Float d // scala.Double u // scala.Unit l // scala.Null n // scala.Nothing L <nullable-type-name> // type-name A <type-name> _ // array type-name X <name> // e xact class type-name <name> //class type-name

11. Native Intermediate Representation (NIR) module @"T5Test$" : @"T6FooCls", @"T8BarTrait" // Class definition noinline def @"M5Test$D4mainLAL16java.lang.String_uEO" : (@"T5Test$", array[@"T16java.lang.String"]) => unit { // Function definition %3(%1 : @"T5Test$", %2 : array[@"T16java.lang.String"]): // Function arguments %4 = var[int] %5 = classalloc @"T8Test$Bar" %6 = call[(@"T8Test$Bar", int) => unit] @"M8Test$BarRiE" : ptr(%5 : !?@"T8Test$Bar", int 42) %7 = method %5 : !?@"T8Test$Bar", "D3intiEO" %8 = call[(@"T8Test$Bar") => int] %7 : ptr(%5 : !?@"T8Test$Bar") %9 = varstore %4 : var[int], %8 : int %10 = varload %4 : var[int] %11 = iadd[int] int 42, %10 : int %12 = imul[int] %11 : int, int 2 %13 = varstore %4 : var[int], %12 : int ret %13 : unit }

12. Pipeline schema

13. Compiler plugin One of last Scala compiler phases Traverses ASTs transforming Class, Def and Val definitions to NIR blocks Collects types informations and attributes from annotations Collects positions from Trees Adapts external function calls Creates binary NIR files

14. Intrinsic functions Defined as Scala Native primitives Not possible to implement in Scala Evaluated in compile-time Used for internal low-level operations: stackalloc, pointer load / store, etc.

15. Linker Loads NIR files based on classpath Performs static reachability checks Discards all not used definitions Collects metadata for classes and members Checks for allocations of classes

16. Optimizer Strongly base of type information inferencing Functions inlining / polymorphic inlining Partial evaluation Partial escape analysis Method deduplication

17. Code generation phase Creating class virtual tables and memory layouts Code injects Main program loop Trait dispatch tables Class / module initializers and accessors Runtime informations and metadata

18. Lowering phase Lowers high-level operations to sequence of low-level instructions Static / dynamic method dispatch Provides handling of runtime exceptions Dead code elimination

19. NIR translation phase Adds LLVM IR headers Deconstifies values some of global values Generates external dependencies declarations Translates NIR into LLVM IR Outputs *.ll files

20. Clang build Compiling native sources Compiling SN code from LLVM IR Linking as one application or shared library

21. A brief comparison with alternatives Part 4

22. Scala Native Roadmap 2021 Part 3

23. Goals for Scala Native in 2021 Support for multithreading Scala 3 frontend Extending available subset of Java standard library Stabilization, bug fixes and performance improvements.