Compiling Imperative and Object-Oriented Languages - Activation Records
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1. Activation records, also known as stack frames, contain information about the execution of methods. 2. They are placed on the call stack and include the method's local variables, partial results, and return address. 3. As methods are invoked, new activation records are pushed onto the stack and popped off when the method returns. 4. The Java Virtual Machine uses a stack-based design where operands are pushed onto the stack, the operation is performed, and results are left on the stack or in local variables.
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Compiling Imperative and Object-Oriented Languages - Activation Records
- 1. Activation Records Guido Wachsmuth Delft Course IN4303, 2012/13 University of Technology Compiler Construction Challenge the future
- 2. Assessment last lecture Given an optimisation step, explain • the optimisation, • its validity, • its benefits. Activation Records 2
- 3. Code Generation function fac0(n0: int): int= .method public static fac0(I)I if n0 = 0 iload 1 then ldc 0 1 if_icmpeq label0 else ldc 0 n0 * fac0(n0 - 1) goto label1 label0: ldc 1 label1: ifeq else0 ldc 1 goto end0 else0: iload 1 iload 1 ldc 1 isub invokestatic Exp/fac0(I)I imul end0: ireturn .end method Activation Records 3
- 4. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload_1 ldc 0 ifne else0 if_icmpeq label0 ldc 0 iconst_1 goto label1 ireturn label0: ldc 1 label1: ifeq else0 else0: iload_1 ldc 1 dup goto end0 iconst_1 else0: iload 1 isub iload 1 invokestatic ldc 1 Exp/fac0(I)I isub imul invokestatic ireturn Exp/fac0(I)I .end method imul end0: ireturn .end method Activation Records 4
- 5. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload 1 ldc 0 ifeq label0 if_icmpeq label0 ldc 0 ldc 0 goto label1 goto label1 label0: ldc 1 label0: ldc 1 label1: ifeq else0 label1: ifeq else0 ldc 1 ldc 1 goto end0 goto end0 else0: iload 1 else0: iload 1 iload 1 iload 1 ldc 1 ldc 1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 5
- 6. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload 1 ifeq label0 ifeq label0 ldc 0 ldc 0 goto label1 ifeq else0 label0: ldc 1 label0: ldc 1 label1: ifeq else0 label1: ifeq else0 ldc 1 ldc 1 goto end0 goto end0 else0: iload 1 else0: iload 1 iload 1 iload 1 ldc 1 ldc 1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 6
- 7. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload 1 ifeq label0 ifeq label0 ldc 0 goto else0 ifeq else0 label0: ldc 1 label0: ldc 1 label1: ifeq else0 label1: ifeq else0 ldc 1 ldc 1 goto end0 goto end0 else0: iload 1 else0: iload 1 iload 1 iload 1 ldc 1 ldc 1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 7
- 8. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload 1 ifeq label0 ifeq label0 goto else0 goto else0 label0: ldc 1 label0: ldc 1 label1: ifeq else0 ifeq else0 ldc 1 ldc 1 goto end0 goto end0 else0: iload 1 else0: iload 1 iload 1 iload 1 ldc 1 ldc 1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 8
- 9. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload 1 ifeq label0 ifeq label0 goto else0 goto else0 label0: ldc 1 label0: ldc 1 ifeq else0 goto end0 ldc 1 else0: iload 1 goto end0 iload 1 else0: iload 1 ldc 1 iload 1 isub ldc 1 invokestatic isub Exp/fac0(I)I invokestatic imul Exp/fac0(I)I end0: ireturn imul .end method end0: ireturn .end method Activation Records 9
- 10. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload 1 ifeq label0 ifneq else0 goto else0 label0: ldc 1 label0: ldc 1 goto end0 goto end0 else0: iload 1 else0: iload 1 iload 1 iload 1 ldc 1 ldc 1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 10
- 11. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload 1 ifneq else0 ifneq else0 label0: ldc 1 ldc 1 goto end0 goto end0 else0: iload 1 else0: iload 1 iload 1 iload 1 ldc 1 ldc 1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 11
- 12. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload 1 ifneq else0 ifneq else0 ldc 1 ldc 1 goto end0 ireturn else0: iload 1 else0: iload 1 iload 1 iload 1 ldc 1 ldc 1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 12
- 13. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload 1 ifneq else0 ifneq else0 ldc 1 ldc 1 ireturn ireturn else0: iload 1 else0: iload 1 iload 1 dup ldc 1 ldc 1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 13
- 14. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload 1 iload_1 ifneq else0 ifneq else0 ldc 1 ldc 1 ireturn ireturn else0: iload 1 else0: iload_1 dup dup ldc 1 ldc 1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 14
- 15. Optimisation .method public static fac0(I)I .method public static fac0(I)I iload_1 iload_1 ifneq else0 ifneq else0 ldc 1 iconst_1 ireturn ireturn else0: iload_1 else0: iload_1 dup dup ldc 1 iconst_1 isub isub invokestatic invokestatic Exp/fac0(I)I Exp/fac0(I)I imul imul end0: ireturn end0: ireturn .end method .end method Activation Records 15
- 16. Overview today’s lecture activation records • procedures in imperative and object-oriented languages • Java Virtual Machine • register-based machines • calling conventions second assignment • general remarks • namespace library • environment library • reports Activation Records 16
- 17. I Java Virtual Machine Term Rewriting 17
- 18. Recap: Modularity procedures imperative languages • subroutines, routines, procedures, functions, methods • scoping: local variables • declarations with parameters (formal parameters) • calls with arguments (actual parameters) • pass by value, pass by reference Activation Records 18
- 19. Recap: Modularity procedures imperative languages • subroutines, routines, procedures, functions, methods • scoping: local variables • declarations with parameters (formal parameters) • calls with arguments (actual parameters) • pass by value, pass by reference machine code • jumps: call and return • call stack: return address, parameters, private data • procedure prologue and epilogue Activation Records 18
- 20. Java Virtual Machine stack frames method area stack pc: 03 optop: 02 local variables 00 2A aload_0 00 4303 4303 00 4303 4303 01 10 bipush 01 0000 0040 01 02 40 02 02 03 B6 invokevirtual 03 03 04 00 04 04 05 01 01 05 05 06 AC ireturn 06 06 heap Activation Records 19
- 21. Java Virtual Machine stack frames method area stack stack pc: 80 optop: 01 optop: 00 local variables local variables 80 2B iload_1 00 4303 4303 00 00 4303 4303 00 4303 4303 81 59 dup 01 0000 0040 01 01 0000 0040 01 82 68 imul 02 02 02 02 83 AC ireturn 03 03 03 03 84 00 04 04 04 04 85 00 05 05 05 05 86 00 06 06 06 06 heap Activation Records 20
- 22. Java Virtual Machine stack frames method area stack stack pc: 81 optop: 01 optop: 01 local variables local variables 80 2B iload_1 00 4303 4303 00 0000 0040 00 4303 4303 00 4303 4303 81 59 dup 01 0000 0040 01 01 0000 0040 01 82 68 imul 02 02 02 02 83 AC ireturn 03 03 03 03 84 00 04 04 04 04 85 00 05 05 05 05 86 00 06 06 06 06 heap Activation Records 21
- 23. Java Virtual Machine stack frames method area stack stack pc: 81 optop: 01 optop: 02 local variables local variables 80 2B iload_1 00 4303 4303 00 0000 0040 00 4303 4303 00 4303 4303 81 59 dup 01 0000 0040 01 0000 0040 01 0000 0040 01 82 68 imul 02 02 02 02 83 AC ireturn 03 03 03 03 84 00 04 04 04 04 85 00 05 05 05 05 86 00 06 06 06 06 heap Activation Records 22
- 24. Java Virtual Machine stack frames method area stack stack pc: 82 optop: 01 optop: 01 local variables local variables 80 2B iload_1 00 4303 4303 00 0000 1000 00 4303 4303 00 4303 4303 81 59 dup 01 0000 0040 01 01 0000 0040 01 82 68 imul 02 02 02 02 83 AC ireturn 03 03 03 03 84 00 04 04 04 04 85 00 05 05 05 05 86 00 06 06 06 06 heap Activation Records 23
- 25. Java Virtual Machine stack frames method area stack pc: 06 optop: 01 local variables 00 2A aload_0 00 0000 1000 00 4303 4303 01 10 bipush 01 01 02 40 02 02 03 B6 invokevirtual 03 03 04 00 04 04 05 01 01 05 05 06 AC ireturn 06 06 heap Activation Records 24
- 26. Example: static call .class public Exp .method public static fac(I)I iload 1 ifne else iconst_1 ireturn else: iload 1 dup iconst_1 isub invokestatic Exp/fac(I)I imul ireturn .end method Activation Records 25
- 27. Example: dynamic call .class public Exp .method public fac(I)I iload 1 ifne else iconst_1 ireturn else: iload 0 iload 1 dup iconst_1 isub invokevirtual Exp/fac(I)I imul ireturn .end method Activation Records 26
- 28. Code Pattern dynamic method call caller • push object • push parameters left-to-right • call method Activation Records 27
- 29. Code Pattern dynamic method call caller • push object • push parameters left-to-right • call method virtual machine on call • allocate space (frame data, operand stack, local variables) • store frame data (data pointer, return address, exception table) • store parameters as local variables • dynamic dispatch • point pc to method code Activation Records 27
- 30. Code Pattern return from method call callee • parameters in local variables • leave result on operand stack • return to caller Activation Records 28
- 31. Code Pattern return from method call callee • parameters in local variables • leave result on operand stack • return to caller virtual machine on return • push result on caller’s operand stack • point pc to return address • destroy frame Activation Records 28
- 32. Implementation heap-based 3 frame data fac(3) 3 2 Activation Records 29
- 33. Implementation heap-based 3 2 frame frame data data fac(2) fac(3) 3 2 Activation Records 29
- 34. Implementation heap-based 3 2 frame frame data data fac(2) fac(3) 3 2 2 Activation Records 29
- 35. Implementation heap-based 3 2 frame frame data data fac(2) fac(3) 3 2 Activation Records 29
- 36. Implementation heap-based 3 2 frame frame data data fac(2) fac(3) 3 2 2 Activation Records 29
- 37. Implementation heap-based 3 2 frame frame data data fac(2) fac(3) 3 2 2 2 Activation Records 29
- 38. Implementation heap-based 3 2 frame frame data data fac(2) fac(3) 3 2 2 2 1 Activation Records 29
- 39. Implementation heap-based 3 2 frame frame data data fac(2) fac(3) 3 2 2 1 Activation Records 29
- 40. Implementation heap-based 3 2 1 frame frame frame data data data fac(2) fac(1) fac(3) 3 2 2 Activation Records 29
- 41. Implementation heap-based 3 2 1 frame frame frame data data data fac(2) fac(1) fac(3) 3 2 1 2 Activation Records 29
- 42. Implementation heap-based 3 2 1 frame frame frame data data data fac(2) fac(1) fac(3) 3 2 2 Activation Records 29
- 43. Implementation heap-based 3 2 1 frame frame frame data data data fac(2) fac(1) fac(3) 3 2 1 2 Activation Records 29
- 44. Implementation heap-based 3 2 frame frame data data fac(2) fac(3) 3 2 2 1 Activation Records 29
- 45. Implementation heap-based 3 2 frame frame data data fac(2) fac(3) 3 2 2 Activation Records 29
- 46. Implementation heap-based 3 frame data fac(3) 3 2 Activation Records 29
- 47. 3 Implementation frame data stack-based fac(3) 3 2 Activation Records 30
- 48. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) Activation Records 30
- 49. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 Activation Records 30
- 50. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) Activation Records 30
- 51. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 Activation Records 30
- 52. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 2 Activation Records 30
- 53. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 2 1 Activation Records 30
- 54. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 1 Activation Records 30
- 55. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 1 frame fac(1) data Activation Records 30
- 56. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 1 frame fac(1) data 1 Activation Records 30
- 57. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 1 frame fac(1) data Activation Records 30
- 58. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 1 frame fac(1) data 1 Activation Records 30
- 59. 3 Implementation frame data stack-based fac(3) 3 2 frame data fac(2) 2 1 Activation Records 30
- 60. 3 Implementation frame data stack-based fac(3) 3 2 Activation Records 30
- 61. coffee break Activation Records 31
- 62. II register-based machines Activation Records 32
- 63. Registers x86 family general purpose registers • accumulator AX - arithmetic operations • counter CX - shift/rotate instructions, loops • data DX - arithmetic operations, I/O • base BX - pointer to data • stack pointer SP, base pointer BP - top and base of stack • source SI, destination DI - stream operations Activation Records 33
- 64. Registers x86 family general purpose registers • accumulator AX - arithmetic operations • counter CX - shift/rotate instructions, loops • data DX - arithmetic operations, I/O • base BX - pointer to data • stack pointer SP, base pointer BP - top and base of stack • source SI, destination DI - stream operations special purpose registers • segments SS, CS, DS, ES, FS, GS • flags EFLAGS Activation Records 33
- 65. Stack and Stack Frames stack • temporary storage • grows from high to low memory addresses • starts at SS Activation Records 34
- 66. Stack and Stack Frames stack • temporary storage • grows from high to low memory addresses • starts at SS stack frames • return address • local variables • parameters • stack base: BP • stack top: SP Activation Records 34
- 67. Calling Conventions CDECL caller • push parameters right-to-left on the stack • clean-up stack after call callee • save old BP • initialise new BP • save registers • return result in AX • restore registers • restore BP Activation Records 35
- 68. Calling Conventions CDECL caller push 21 push 42 • push parameters right-to-left on the stack call add _f ESP 8 • clean-up stack after call callee • save old BP • initialise new BP • save registers • return result in AX • restore registers • restore BP Activation Records 35
- 69. Calling Conventions CDECL caller push 21 push 42 • push parameters right-to-left on the stack call add _f ESP 8 • clean-up stack after call callee • save old BP push EBP • initialise new BP mov mov EBP EAX ESP [EBP + 8] • save registers mov EDX [EBP + 12] • return result in AX add pop EAX EBP EDX • restore registers ret • restore BP Activation Records 35
- 70. Calling Conventions STDCALL caller • push parameters right-to-left on the stack callee • save old BP • initialise new BP • save registers • return result in AX • restore registers • restore BP Activation Records 36
- 71. Calling Conventions STDCALL caller push 21 push 42 • push parameters right-to-left on the stack call _f@8 callee • save old BP • initialise new BP • save registers • return result in AX • restore registers • restore BP Activation Records 36
- 72. Calling Conventions STDCALL caller push 21 push 42 • push parameters right-to-left on the stack call _f@8 callee • save old BP • initialise new BP push EBP • save registers mov mov EBP EAX ESP [EBP + 8] • return result in AX mov EDX [EBP + 12] • restore registers add pop EAX EBP EDX • restore BP ret 8 Activation Records 36
- 73. Calling Conventions FASTCALL caller • passes parameters in registers • pushes additional parameters right-to-left on the stack callee • save old BP, initialise new BP • save registers • return result in AX • restore registers • restore BP • cleans up the stack Activation Records 37
- 74. Calling Conventions FASTCALL caller mov ECX 21 mov EDX 42 • passes parameters in registers call @f@8 • pushes additional parameters right-to-left on the stack callee • save old BP, initialise new BP • save registers • return result in AX • restore registers • restore BP • cleans up the stack Activation Records 37
- 75. Calling Conventions FASTCALL caller mov ECX 21 mov EDX 42 • passes parameters in registers call @f@8 • pushes additional parameters right-to-left on the stack callee • save old BP, initialise new BP push EBP • save registers mov mov EBP ESP EAX ECX • return result in AX add EAX EDX • restore registers pop ret EBP • restore BP • cleans up the stack Activation Records 37
- 76. III optimisations revisited Term Rewriting 38
- 77. Optimisations reasons • code overhead • execution overhead Activation Records 39
- 78. Optimisations reasons • code overhead • execution overhead inlining • replace calls by body of the procedure • source code level Activation Records 39
- 79. Optimisations reasons • code overhead • execution overhead inlining • replace calls by body of the procedure • source code level tail recursion • replace recursive calls by loops or jumps • source or machine code level Activation Records 39
- 80. Example: Tail Recursion .class public Exp .method public static fac(I)I iload 1 ifne else iconst_1 ireturn else: iload 1 dup iconst_1 isub invokestatic Exp/fac(I)I imul ireturn .end method Activation Records 40
- 81. Example: Tail Recursion .class public Exp .method public static fac(II)I iload 1 ifne else iload 2 ireturn else: iload 1 iconst_1 isub iload 1 iload 2 imul invokestatic Exp/fac(II)I ireturn .end method Activation Records 41
- 82. Example: Tail Recursion .class public Exp .method public static fac(II)I strt: iload 1 ifne else iload 2 ireturn else: iload 1 iconst_1 isub iload 1 iload 2 imul istore 2 istore 1 goto strt Activation Records 42
- 83. IV summary Term Rewriting 43
- 84. Summary lessons learned stack frames in the Java Virtual Machine • parameter passing, returning results • implementation strategies Activation Records 44
- 85. Summary lessons learned stack frames in the Java Virtual Machine • parameter passing, returning results • implementation strategies stack frames in register-based machines • registers x86 family • manipulating stack registers • calling conventions Activation Records 44
- 86. Summary lessons learned stack frames in the Java Virtual Machine • parameter passing, returning results • implementation strategies stack frames in register-based machines • registers x86 family • manipulating stack registers • calling conventions optimisations Activation Records 44
- 87. Literature learn more Java Virtual Machine Tim Lindholm, Frank Yellin: The Java Virtual Machine Specification, 2nd edition. Addison-Wesley, 1999. Bill Venners: Inside the Java 2 Virtual Machine. McGraw-Hill, 2000. Activation Records 45
- 88. Literature learn more Java Virtual Machine Tim Lindholm, Frank Yellin: The Java Virtual Machine Specification, 2nd edition. Addison-Wesley, 1999. Bill Venners: Inside the Java 2 Virtual Machine. McGraw-Hill, 2000. Activation Records Andrew W. Appel, Jens Palsberg: Modern Compiler Implementation in Java, 2nd edition. 2002 Activation Records 45
- 89. Outlook coming next imperative and object-oriented languages • Lecture 10: Dataflow Analysis Nov 13 • Lecture 11: Register Allocation Nov 20 • Lecture 12: Garbage Collection Nov 27 Lab Oct 25 • name analysis • name-based errors • type analysis for named elements • type-based errors Activation Records 46
- 90. copyrights & credits Activation Records 47
- 92. Pictures copyrights Slide 1: Framed by LexnGer, some rights reserved Slide 37: The Lemon Tree by Dominica Williamson, some rights reserved Slide 46: Oude Kerk by M.M. R, some rights reserved Activation Records 49
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- round-up on every lecture\n\nwhat to take with you\n\ncheck yourself, pre- and post-paration\n
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