1. © Oscar Nierstrasz ST — Introduction ST 1.1 The Smalltalk Compiler

2. © Oscar Nierstrasz ST — Introduction ST 1.2 Compiler  Fully reified compilation process: —Scanner/Parser (built with SmaCC) – builds AST (from Refactoring Browser) —Semantic Analysis: ASTChecker – annotates the AST (e.g., var bindings) —Translation to IR: ASTTranslator – uses IRBuilder to build IR (Intermediate Representation) —Bytecode generation: IRTranslator – uses BytecodeBuilder to emit bytecodes

3. © Oscar Nierstrasz ST — Introduction ST 1.3 Compiler: Overview code AST Scanner / Parser Scanner / Parser Semantic Analysis Semantic Analysis Bytecode Code Generation Code Generation AST IR Build IR Build IR Bytecode Generation Bytecode Generation ASTTranslator IRBuilder IRTranslator BytecodeBuilder Code generation in detail

4. © Oscar Nierstrasz ST — Introduction ST 1.4 Compiler: Syntax  SmaCC: Smalltalk Compiler Compiler —Like Lex/Yacc —Input: – Scanner definition: regular expressions – Parser: BNF-like grammar – Code that builds AST as annotation —SmaCC can build LARL(1) or LR(1) parser —Output: – class for Scanner (subclass SmaCCScanner) – class for Parser (subclass SmaCCParser)

5. © Oscar Nierstrasz ST — Introduction ST 1.5 Scanner

6. © Oscar Nierstrasz ST — Introduction ST 1.6 Parser

7. © Oscar Nierstrasz ST — Introduction ST 1.7 Calling Parser code

8. © Oscar Nierstrasz ST — Introduction ST 1.8 Compiler: AST  AST: Abstract Syntax Tree —Encodes the Syntax as a Tree —No semantics yet! —Uses the RB Tree: – visitors – backward pointers in ParseNodes – transformation (replace/add/delete) – pattern directed TreeRewriter – PrettyPrinter RBProgramNode RBDoItNode RBMethodNode RBReturnNode RBSequenceNode RBValueNode RBArrayNode RBAssignmentNode RBBlockNode RBCascadeNode RBLiteralNode RBMessageNode RBOptimizedNode RBVariableNode RBProgramNode RBDoItNode RBMethodNode RBReturnNode RBSequenceNode RBValueNode RBArrayNode RBAssignmentNode RBBlockNode RBCascadeNode RBLiteralNode RBMessageNode RBOptimizedNode RBVariableNode

9. © Oscar Nierstrasz ST — Introduction ST 1.9 Compiler: Semantics  We need to analyse the AST —Names need to be linked to the variables according to the scoping rules  ASTChecker implemented as a Visitor —Subclass of RBProgramNodeVisitor —Visits the nodes —Grows and shrinks scope chain —Methods/Blocks are linked with the scope —Variable definitions and references are linked with objects describing the variables

10. © Oscar Nierstrasz ST — Introduction ST 1.10 A Simple Tree

11. © Oscar Nierstrasz ST — Introduction ST 1.11 A Simple Visitor RBProgramNodeVisitor new visitNode: tree Does nothing except walk through the tree

12. © Oscar Nierstrasz ST — Introduction ST 1.12 TestVisitor RBProgramNodeVisitor subclass: #TestVisitor instanceVariableNames: 'literals' classVariableNames: '' poolDictionaries: '' category: 'Compiler-AST-Visitors' TestVisitor>>acceptLiteralNode: aLiteralNode literals add: aLiteralNode value. TestVisitor>>initialize literals := Set new. TestVisitor>>literals ^literals RBProgramNodeVisitor subclass: #TestVisitor instanceVariableNames: 'literals' classVariableNames: '' poolDictionaries: '' category: 'Compiler-AST-Visitors' TestVisitor>>acceptLiteralNode: aLiteralNode literals add: aLiteralNode value. TestVisitor>>initialize literals := Set new. TestVisitor>>literals ^literals tree := RBParser parseExpression: '3 + 4'. (TestVisitor new visitNode: tree) literals tree := RBParser parseExpression: '3 + 4'. (TestVisitor new visitNode: tree) literals a Set(3 4)

13. © Oscar Nierstrasz ST — Introduction ST 1.13 Compiler: Intermediate Representation  IR: Intermediate Representation —Semantic like Bytecode, but more abstract —Independent of the bytecode set —IR is a tree —IR nodes allow easy transformation —Decompilation to RB AST  IR build from AST using ASTTranslator: —AST Visitor —Uses IRBuilder

14. © Oscar Nierstrasz ST — Introduction ST 1.14 Compiler: Bytecode Generation  IR needs to be converted to Bytecode —IRTranslator: Visitor for IR tree —Uses BytecodeBuilder to generate Bytecode —Builds a compiledMethod testReturn1 | iRMethod aCompiledMethod | iRMethod := IRBuilder new numRargs: 1; addTemps: #(self);"receiver and args declarations" pushLiteral: 1; returnTop; ir. testReturn1 | iRMethod aCompiledMethod | iRMethod := IRBuilder new numRargs: 1; addTemps: #(self);"receiver and args declarations" pushLiteral: 1; returnTop; ir. aCompiledMethod := iRMethod compiledMethod. self should: [(aCompiledMethod valueWithReceiver: nil arguments: #() ) = 1]. aCompiledMethod := iRMethod compiledMethod. self should: [(aCompiledMethod valueWithReceiver: nil arguments: #() ) = 1]. CHECK the example!