Compiler construction in4020 – lecture 11

1. Compiler constructionin4020 – lecture 11 Koen Langendoen Delft University of Technology The Netherlands

2. Assignment 1: results • test results (3-14) • expression priorities • error recovery • corner cases • code (5-7) • Makefile • documentation (5-7) • 2 pages!! thoroughly test your compiler

3. ptr to B ptr to A inside B a1 m1_A_A a2 m2_A_B b1 m3_B_B B-object B-class Summary of lecture 10 • assemblers & linkers • OO programming • translation to C • method tables

4. Quiz [Assignment 2]Which of the following features are part of OO-Asterix? • inheritance • method overriding • polymorphism • dynamic binding • (dependent) multiple inheritance Do we need method tables? If so, which flavor?

5. Overview • routine types • activation records • invocation • values • code generation for control flow statements • boolean expressions • selection statements • repetition statements

6. Routines and their activations • functionality of a routine call • supplying a new computing environment • passing information to the new environment • transfer of the flow-of-control to the new environment and (guaranteed) return • returning info from the new environment

7. Activation records parameter k ... parameter 1 • activation record holds • local variables • parameters • working stack • administration part • routine activation order • last-in-first-out stack • otherwise  heap lexical pointer registers dynamic link return info frame ptr local variables FP working stack stack ptr SP

8. parameter k parameter 1 ... Routine invocation registers dynamic link return address FP • caller builds new stack frame for callee • push parameters • push admin • transfer control to callee • stack return address, adjust FP • allocate space for local vars • execute code local variables working stack SP

9. parameter n parameter 1 parameter k parameter 1 ... ... Routine invocation registers dynamic link return address FP • caller builds new stack frame for callee • push parameters • push admin • transfer control to callee • stack return address, adjust FP • allocate space for local vars • execute code local variables working stack SP

10. parameter n parameter 1 parameter k parameter 1 ... ... Routine invocation registers dynamic link return address FP • caller builds new stack frame for callee • push parameters • push admin • transfer control to callee • stack return address, adjust FP • allocate space for local vars • execute code local variables working stack registers dynamic link return address SP

11. parameter n parameter 1 parameter k parameter 1 ... ... Routine invocation registers dynamic link return address • caller builds new stack frame for callee • push parameters • push admin • transfer control to callee • stack return address, adjust FP • allocate space for local vars • execute code local variables working stack registers dynamic link return address SP FP

12. parameter n parameter 1 parameter k parameter 1 ... ... Routine invocation registers dynamic link return address • caller builds new stack frame for callee • push parameters • push admin • transfer control to callee • stack return address, adjust FP • allocate space for local vars • execute code local variables working stack registers dynamic link return address FP local variables SP

13. parameter n parameter 1 parameter k parameter 1 ... ... Routine invocation registers dynamic link return address • caller builds new stack frame for callee • push parameters • push admin • transfer control to callee • stack return address, adjust FP • allocate space for local vars • execute code local variables working stack registers dynamic link return address FP local variables working stack SP

14. aap mies parameter i parameter i static link dynamic link return address static link dynamic link return address noot parameter i static link dynamic link return address Nested routines • activation record contains a lexical pointer or static link that points to outer scope int aap( int i) { int noot() {return i+7;} int mies(int i) {return i+noot();} return mies(2)-3; }

15. Exercise (5 min.) • Given the GNU C routine: a) draw the stack that results from the call A(2) b) how does C access the parameter (a) from A? void A(int a) { void B(int b) { void C(void) { printf(“C called, a = %d\n”, a); } if (b == 0) C() else B(b-1); } B(a); }

16. Answers

17. dynamic links static links A 2 B 2 B 1 B 0 C Answers FP->static_link->static_link->param[#i]

18. Break

19. Operations on routines • calling • passing as a parameter • returning as a value • currying [functional programming, chap 7]

20. flat int aap(int i) {return i+7;} int noot(int i, int (*f)(int)) {return (*f)(i);} int mies(int i) {return noot(i,aap);} address nested int noot(int (*f)()) {return (*f)();} int mies(int i) { int aap() {return i+7;} return noot(aap); } static link address Passing a routine as a parameter

21. flat typedef int (*fptr)(int); int aap(int i) {return i+7;} fptr mies() {return aap;} nested typedef int (*fptr)(); fptr mies(int i) { int aap() {return i+7;} return aap; } return routine descriptor Returning a routine as a value return routine address and allocate activation records on the heap

22. Lambda lifting • remove static links, only global routines • out-of-scope variables • referencing: pass additional pointers • creating: heap allocation int aap(int *i) {return *i+7;} fptr mies(int i) { int *_i = malloc(sizeof(i)); *_i = i; return closure(aap,_i); } typedef int (*fptr)(); fptr mies(int i) { int aap() {return i+7;} return aap; } nested lifted

23. cmpl %eax,%edx jle L3 Code generation forcontrol flow statements • glue between basic blocks

24. Boolean expressionsin flow of control • why special code generation? • performance: avoid conversions • lazy semantics: || and && in C Code expr( ”list != NULL”, r1) Code expr( ” list->key < key”, r2) IF NOT(r1 and r2) THEN GOTO label-end … label-end: if (list != NULL && list->key < key) { ... }

25. PROCEDURE Boolean control code(Node, True label, False label): SELECT Node.type CASE Lazy and type: Boolean control code( Node.left, No label, False label); Boolean control code( Node.right, True label, False label); CASE Lazy or type: Boolean control code( Node.left, True label, No label); Boolean control code( Node.right, True label, False label); CASE Comparison type: Code expr( Node.left, R1) Code expr( Node.right, R2); IF True label /= No label): Emit(”IF” R1 Node.op R2 ”THEN GOTO” True label); IF False label /= No label): Emit( ”GOTO” False label); ELSE Emit(”IF” R1 Inv(Node.op) R2 ”THEN GOTO” False label); PROCEDURE Boolean control code(Node, True label, False label): SELECT Node.type CASE Lazy and type: Boolean control code( Node.left, No label, False label); Boolean control code( Node.right, True label, False label); CASE Lazy or type: Boolean control code( Node.left, True label, No label); Boolean control code( Node.right, True label, False label); CASE Comparison type: Code expr( Node.left, R1) Code expr( Node.right, R2); IF True label /= No label): Emit(”IF” R1 Node.op R2 ”THEN GOTO” True label); IF False label /= No label): Emit( ”GOTO” False label); ELSE Emit(”IF” R1 Inv(Node.op) R2 ”THEN GOTO” False label); PROCEDURE Boolean control code(Node, True label, False label): SELECT Node.type CASE Lazy and type: Boolean control code( Node.left, No label, False label); Boolean control code( Node.right, True label, False label); CASE Lazy or type: Boolean control code( Node.left, True label, No label); Boolean control code( Node.right, True label, False label); CASE Comparison type: Code expr( Node.left, R1) Code expr( Node.right, R2); IF True label /= No label): Emit(”IF” R1 Node.op R2 ”THEN GOTO” True label); IF False label /= No label): Emit( ”GOTO” False label); ELSE Emit(”IF” R1 Inv(Node.op) R2 ”THEN GOTO” False label); PROCEDURE Boolean control code(Node, True label, False label): SELECT Node.type CASE Lazy and type: Boolean control code( Node.left, No label, False label); Boolean control code( Node.right, True label, False label); CASE Lazy or type: Boolean control code( Node.left, True label, No label); Boolean control code( Node.right, True label, False label); CASE Comparison type: Code expr( Node.left, R1) Code expr( Node.right, R2); IF True label /= No label): Emit(”IF” R1 Node.op R2 ”THEN GOTO” True label); IF False label /= No label): Emit( ”GOTO” False label); ELSE Emit(”IF” R1 Inv(Node.op) R2 ”THEN GOTO” False label); PROCEDURE Boolean control code(Node, True label, False label): SELECT Node.type CASE Lazy and type: Boolean control code( Node.left, No label, False label); Boolean control code( Node.right, True label, False label); CASE Lazy or type: Boolean control code( Node.left, True label, No label); Boolean control code( Node.right, True label, False label); CASE Comparison type: Code expr( Node.left, R1) Code expr( Node.right, R2); IF True label /= No label): Emit(”IF” R1 Node.op R2 ”THEN GOTO” True label); IF False label /= No label): Emit( ”GOTO” False label); ELSE Emit(”IF” R1 Inv(Node.op) R2 ”THEN GOTO” False label);

26. The if-statement if -statement condition true stmt false stmt IF THEN ELSE Boolean control code( condition, No_label, false_label) Code statement( true stmt) GOTO end_label; false_label: Code statement( false stmt) end_label:

27. The if-statement if -statement condition true stmt false stmt IF THEN ELSE Boolean control code( condition, No_label, false_label) Code statement( true stmt) GOTO end_label: false_label: Code statement( false stmt) end_label: Boolean control code( condition, No_label, end_label) Code statement( true stmt) end_label:

28. The case-statement Code expr( expression, Rexpr) IF Rexpr = I1 THEN GOTO label_1 ... IF Rexpr = In THEN GOTO label_n GOTO label_else; label_1: Code statement (statement1) GOTO end_label; ... label_n: Code statement (statementn) GOTO end_label; label_else: Code statement (statementdefault) end_label: CASE expressionIN I1: statement1 ... In: statementn ELSE statementdefault END CASE

29. jump table .data case_table: label_low ... label_high The case-statement CASE expressionIN I1: statement1 ... In: statementn ELSE statementdefault END CASE Code expr( expression, Rexpr) IF Rexpr < Ilow THEN GOTO label_else IF Rexpr > Ihigh THEN GOTO label_else GOTO case_table[Rexpr- Ilow]; label_1: ...

30. The while-statement while -statement condition statement WHILE DO END WHILE test_label: Boolean control code( condition, No_label, end_label) Code statement( statement) GOTO test_label; end_label: GOTO test_label; loop_label: Code statement( statement) test_label: Boolean control code( condition, loop_label , No_label)

31. Code expr( lower bound, Ri) Code expr( upper bound, Rub) IF Ri > Rub THEN GOTO end_label loop_label: Code statement (statement) IF Ri = Rub THEN GOTO end_label Ri := Ri+1; GOTO loop_label; end_label: i:=lower bound; tmp_ub:=upper bound; WHILE i <= tmp_ub DO statement i := i+1; END FOR test before increment The for-statement FOR i IN lower bound.. upper bound DO statement END FOR

32. Exercise (3 min.) • give a translation schema for repeat statements repeat -statement statement condition REPEAT UNTIL END REPEAT

33. Answers

34. Answers repeat -statement statement condition REPEAT UNTIL END REPEAT repeat_label: Code statement( statement) Boolean control code( condition, No_label , repeat_label)

35. mies parameter i static link dynamic link return address noot parameter i static link dynamic link return address Summary • (nested) routines • activation records • routine descriptors • code generation for control flow statements • conditional expressions: true & false labels • case-statement: jump table • for-statement: overflow

36. Homework • study sections: • 6.5Code generation for modules • assignment 2: • make Asterix OO • deadline June 4 08:59 • print handout for next week [blackboard]