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The Tiger compiler

The Tiger compiler. Ivan Pribela. Contents. The Tiger language Course structure Course sequence Object-oriented Tiger language Functional Tiger language Existing course adaption to Tiger. Tiger compiler. The Tiger language. The Tiger language. Tiger programming language

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The Tiger compiler

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  1. The Tiger compiler Ivan Pribela

  2. Contents • The Tiger language • Course structure • Course sequence • Object-oriented Tiger language • Functional Tiger language • Existing course adaption to Tiger

  3. Tiger compiler The Tiger language

  4. The Tiger language • Tiger programming language • is simple, but nontrivial language • belongs to Algol family with nested scope • heap-allocated records with implicit pointers • arrays, integer and string variables • few simple structured control constructs • Easily modified to • a functional programming language • be object-oriented

  5. Sample Tiger programs let var a := 0 in for i := 0 to 100 do ( a := a + 1; () ) end let function do_nothing1(a: int, b: string): int = ( do_nothing2(a + 1); 0 ) function do_nothing2(d: int): string = ( do_nothing1(d, “str”); “ ” ) in do_nothing1(0, “str2”) end

  6. Lexical issues • Identifiers • sequence of letters, digits and underscores, starting with letter • Comments • starting with /* and ending with */ • can apear betwean any two tokens • can be nested

  7. decs→ { dec } dec→ tydec | vardec | fundec Declarations • Declaration sequence • a sequence of type, value and function declarations • no punctation separates or terminates individual declarations

  8. tydec→ type id = ty ty→ id | { tyfld } | arrayof id tyfld→ λ| id : type-id {, id : type-id } Data Types • Built-in types • int and string • ca be redefined • Type equality • by name • Mutually recursive • consecutive sequence • list = {hd: int, tl: list} • Field name reusability

  9. vardec→ var id := exp | var id [: type-id ] := exp Variables • Variable type • in short form, type of the expression is used • in long form, given type and type of expression must match • if expression is nil, long fom must be used • Variable lasts until end of scope

  10. fundec→ function id ( tyfld ) = exp | function id ( tyfld ): type-id = exp Functions • Parameters • all parameters are passed by value • Mutually recursive • declared in consecutive sequence

  11. Scope rules • Variables • let ... vardec ... in exp end • Parameters • function id ( ... id1 : id2 ... )= exp • Nested scopes • access to a variable in outer scopes is permited • Types • let ... typedec ... in exp end

  12. Scope rules • Functions • let ... fundec ... in exp end • Name spaces • two name spaces (types, varables & functions) • Local redeclarations • object can be hidden in a smaller scope • mutually recurcive objects must have different names

  13. fundec→ function id ( tyfld ) =exp | function id ( tyfld ): type-id = exp Values • L-values • location whose value may be read or assigned • variables, procedure parameters, fields of records and elements of the array

  14. Expressions • L-value • evaluates to the location contents • Valueless expressions • procedure calls, assignment, if-then, while, break, and sometimes if-then-else • Nil • expression nil denotes a value nil • when used, it must have a type determined • Sequencing • sequence of expressions (exp1; exp2; ... expn)

  15. Expressions • No value • empty sequence • let expression with empty in...end • Integer literal • sequence of digits • String literal • sequence of 0 or more printable characters betwean quotes • \\ \n \t \ddd \” \f...f\ • Negation • Function call • has value of function result, or produces no value

  16. Operations • Arithmetic operators • + - * / • Comparison • = < > <= >= <> • produces: 0 for false, 1 for true • Boolean operators • & | • 0 is considered false, non zero is true

  17. Records and arrays • Record creation • type-id { id = exp { , id = exp} } • Array creation • type-id [ exp1]of exp2 • Assignment and Extent • records and arrays assignmen is by reference • records and arrays have infinite extent

  18. Statements • If-then-else • if exp1then exp2 [ else exp3 ] • exp2 and exp3 must be the same type • While loop • while exp1do exp2 • For loop • for id := exp1to exp2do exp3

  19. Statements • Break • terminates evaluation of nearest while or for • Let • let desc in expseq end • evaluates desc • binds types variables and functions • result (if any) is the result of last expression • Parentheses

  20. Standard library function print (s: string) function flush () function getchar (): string function ord (s: string): int function chr (i: int): string function not (i: int): int function exit (i: int) function size (s: string): int function substring ( s: string, first: int, n: int ): string function concat ( s1: string, s2: string ): string

  21. Tiger compiler Course structure

  22. Lectures • Lectures • Students will see the theory behind different components of a compiler • programming techniques used to put the theory into practice • and the interfaces used to modularize the compiler • written in Java programming language

  23. Practical exercises • Practical exercises • The “student project compiler” is reasonably simple • is organized to demonstrate some important techniques • Use abstract syntax trees to avoid tangling syntax and semantics • separates instruction selection from register allocation

  24. Paper exercises • Each chapter has pencil-and-paper exercises • marked with a star are more challenging • two-star problems are difficult but solvable • occasional three-star exercises are not known to have a solution.

  25. Topic dependancy

  26. One or two semester course • One-semester course could cover all of Part I • Chapters 1-12 • students implement the project compiler • working in groups • in addition, selected topics from Part II. • An advanced or graduate course – cover Part II • as well as additional topics from the other literature • many of the Part II chapters can stand independently • In a two-quarter sequence • the first quarter could cover Chapters 1-8 • and the second quarter could cover Chapters 9-12 • and some chapters from Part II

  27. Course material • Chapters in Part I • are acompanied by skeleton code • easily built to a full working compiler module • can be used on practical exercises • Chapters in Part II • give only theorethical knoledge • and general instructions how to add discused feature to the Tiger compiler • there is no skeleton code

  28. Target language • RISC • 32 registers • only one class of integer/pointer registers • arithmetic operations only betwean registers • tree-address instructions of form r1r23 • load and store only with M[reg+const] addressing • every instruction is 32bit long • one result effect per instruction • CISC • few registers (16, 8, or 6) • registers divided in to classes • some operations available only on certain registers • aritmetic operations on registers and memory • two-address instructions of form r1r23 • various addressing modes • variable length instructions • instructions with side effects

  29. Tiger compiler Course sequence

  30. Course sequence 1. Introduction 2. Lexical analysis • Phases • each phase is described in one section • some compilers combine parse, semantic analysis • others put instruction selection much later • simple compilers omit control and dataflow analysis 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  31. Introduction 1. Introduction 1. Introduction 2. Lexical analysis • Modules and interfaces • large software is much easies to understand • and to implement • Tools and software • context-free grammars • reguar expressions • Data structures • intermediate representations • tables, trees 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  32. 2. Lexical analysis Lexical analysis 1. Introduction 2. Lexical analysis • Transforms program text • reads program text • outputs sequence of tokens • Algorithm • generated from lexical specification • JLex lexer generator 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  33. 3. Parsing Parsing 1. Introduction 2. Lexical analysis • Checks program syntax • detects errors in order of tokens • Parsing algorithm • LALR(1) - parsing • CUP parser generator 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  34. 4. Abstract syntax Abstract syntax 1. Introduction 2. Lexical analysis • Improves modularuty • syntax analysis is separated form semantic analysis • Semantic actions • during parsing • produce abstract parse tree 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  35. 5. Semantic analysis Semantic analysis 1. Introduction 2. Lexical analysis • Checks program semantic • reports scope and type errors • Actions • builds symbol tables • performes scope analysis • checks types 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  36. 6. Activation records Activation records 1. Introduction 2. Lexical analysis • Functions, local variables • several invocations of the same function may coexist • each invocation has its own instances of local variables • Stack frames • local variables, parameters • return address, temporaries • static and dynamic links 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  37. 7. Intermediate code Intermediate code 1. Introduction 2. Lexical analysis • Allows portability • only N front ends and M back ends • Abstract machine language • can express target machine operations • indipendent of details of cource language • represented by simple expression trees 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  38. Intermediate code a + b * 4 if a = b then break else x:= 5

  39. 8. Blocks and traces Blocks and traces 1. Introduction 2. Lexical analysis • Basic blocks • begins with a label • ends with jump • no other labels or jumps • Traces • blocks can be arranged in any order • arrange that most jumps are followed by their label 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  40. 9. Instruction selection Instruction selection 1. Introduction 2. Lexical analysis • Allows portability • finding apropriate machine instructions to implement IR • Tree patterns • one pattern represents one instruction • instruction selection is tiling of IR tree 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  41. Instruction selection LOAD r1 → M [fp + a] ADDI r2 → r0 + 4 MUL r2 → ri x r2 ADD r1 → r1 + r2 LOAD r2 → M [fp + x] STORE M [r1 + 0] → r2 LOAD r1 → M [fp + a] ADDI r2 → r0 + 4 MUL r2 → ri x r2 ADD r1 → r1 + r2 ADDI r2 → fp + x MOVE M [r1] → M [r2]

  42. 10. Liveness analysis Leveness analysis 1. Introduction 2. Lexical analysis • Detects needed values • determines which variable will be needed in the future • Problem • IR has unbounded number of temporaries • target machine has limited number of registers • Solution • Control and dataflow graph 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  43. 11. Register allocation Register allocation 1. Introduction 2. Lexical analysis • Assignes registers • links temporaries with registers • Interference graph • is created from examination of control and dataflow graph • is colored for registers to be assigned 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  44. 12. Putting all together Putting it all together 1. Introduction 2. Lexical analysis • Properties • nested functions • missing structured values • tree intermediate representations • register allocation • Remains • list all registers • procedure entry / exit • implement strings 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 11. Register allocation 5. Semantic analysis 8. Blocks and traces 12. Putting all together

  45. 17. Dataflow analysis 18. Loop optimizations 19. Static single assignment form 20. Pipelinining, scheduling 21. Memory hierarchies Optimizations 1. Introduction 2. Lexical analysis • Optimizing compiler • transforms programs to improve efficiency • uses dataflow analysis • Algorithms • Static single assignment form • use pipelining if available • utilize cache 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 17. Dataflow analysis 11. Register allocation 5. Semantic analysis 8. Blocks and traces 18. Loop optimizations 19. Static single assignment form 12. Putting all together 12. Putting all together 20. Pipelinining, scheduling 13. Garbage collection 21. Memory hierarchies

  46. Garbage collection 1. Introduction 2. Lexical analysis • Algorithms • mark and sweep • reference counts • copying collection • generational collection • Incremental collection 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 17. Dataflow analysis 11. Register allocation 5. Semantic analysis 8. Blocks and traces 18. Loop optimizations 19. Static single assignment form 12. Putting all together 12. Putting all together 20. Pipelinining, scheduling 13. Garbage collection 13. Garbage collection 21. Memory hierarchies

  47. 16. Polymorphic types Language modifications 14. Object-oriented languages 14. Object-oriented languages 1. Introduction 15. Functional languages 15. Functional languages 2. Lexical analysis 16. Polymorphic types 6. Activation records 3. Parsing 9. Instruction selection 10. Liveness analysis 4. Abstract syntax 7. Intermediate code 17. Dataflow analysis 11. Register allocation 5. Semantic analysis 8. Blocks and traces 18. Loop optimizations 19. Static single assignment form 12. Putting all together 20. Pipelinining, scheduling 13. Garbage collection 21. Memory hierarchies

  48. Tiger compiler Object-oriented Tiger language

  49. Object-oriented principles • Information hiding • Useful software principle • module provide values of given type • only that module knows its representation • Extension • inheritance Object-Tiger Tiger can easily become object oriented

  50. Program example let start := 10 class Vehicle extends Object { var position := start method move (int x)= ( position := position + x ) } class Truck extends Vehicle { method move (int x)= if x <= 80 then position := position + x } var t :=new Truck var v: Vehicle := t in t.move(50) v.move(100) end

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