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Code Generation Example Mooly Sagiv html://www.cs.tau.ac.il/~msagiv/courses/wcc06.html
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Basic Compiler Phases
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Outline A possible structure of the activation records Example compilation Executing the assembly code
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Typical Virtual Memory Content Lower addresses static area Stack area Heap area Machine Registers
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The problem The compiler needs to allocate memory for variables Consistent with program semantics –Scope –Duration –Recursion Efficient (moderate runtime cost) Solution?
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A Typical Stack Frame
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Example Program
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part SP FP R03 R1 R2 main
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R03 R1 R2 Administrative part SP FP main fact
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R02 R1 R2 Administrative part SP FP main fact 5 3
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R02 R1 R2 Administrative part SP FP main fact 5 3 Administrative part fact 5
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R01 R1 R2 Administrative part SP FP main fact 5 3 Administrative part fact 5 2
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R01 R1 R2 Administrative part main fact 5 3 Administrative part fact 5 2 SP FP Administrative part fact 5
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R00 R1 R2 Administrative part main fact 5 3 Administrative part fact 5 2 SP FP Administrative part fact 5 1
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R00 R1 R2 Administrative part main fact 5 3 Administrative part fact 5 2 SP FP Administrative part fact 5 Administrative part fact 5 1
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R01 R11 R2 Administrative part main fact 5 3 Administrative part fact 5 2 SP FP Administrative part fact 5 1
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R01 R12 R2 Administrative part main fact 5 3 Administrative part fact 5 2 SP FP
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R02 R13 R2 Administrative part main fact 5 3 SP FP
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R0x87 R16 R2 main SP FP x87 “%d\n”
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void main() { printf(“%d\n”, fact(3)); } int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } Administrative part R0x87 R16 R2 main SP FP x87 “%d\n” Administrative part _printf
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Register Instructions InstructionActions Load_Const c, RiRi=c Load_Local c(Ri), RjRj=*(Ri+c) Store_Local Ri, c(Rj)*(Rj+c)=Ri Add_Constant c, RiRi = Ri+c Add_Reg Ri, RjRj = Rj+Ri CMP Ri, RjCC = Ri -Rj CMP_Const C, RiCC = Ri - C Branch LPC = L; Branch_EQ Lif (CC==EQ) PC =L JSR L*(--SP) = FP; *(--SP) = PC; FP=SP-1;PC =L RTSPC=*(SP++); FP=*(SP++)
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void main() { printf(“%d\n”, fact(3)); }. global _main Add_Constant -K1, SP L1: Load_Const 3, R0 JSR _fact Load_Reg R0, R1 Load_Const L2, R0 JSR _printf Add_Constant K1, SP RTS.data L2 : “%d\n”.end Code Generated for ‘main’
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Code generated for ‘fact’ int fact(int n) { if (n==0) return 1; else return n * fact(n-1) ; } L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end Administrative part SP FP R03 R1 R2 main Administrative part
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end Administrative part SP FP R03 R1 R2 main Administrative part fact
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end Administrative part SP FP R03 R1 R2 main Administrative part fact
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end Administrative part SP FP R03 R1 R2 main Administrative part fact
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end Administrative part SP FP R03 R1 R2 main Administrative part fact
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end Administrative part SP FP R03 R1 R2 main Administrative part fact 5 3
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end Administrative part SP FP R02 R1 R2 main Administrative part fact 5 3
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end Administrative part R02 R1 R2 main Administrative part fact 5 3 SP FP Administrative part
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end Administrative part R02 R1 R2 main Administrative part fact 5 3 SP FP Administrative part fact 5
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L6: Add_Constant K2, SP RTS.end R00 R1 R2 Administrative part fact 5 3 Administrative part fact 5 2 SP FP Administrative part fact 5 Administrative part fact 5 1 Administrative part main
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 L6: Add_Constant K2, SP RTS.end R00 R1 R2 Administrative part fact 5 3 Administrative part fact 5 2 SP FP Administrative part fact 5 Administrative part fact 5 1 Administrative part main
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 R01 R1 R2 Administrative part fact 5 3 Administrative part fact 5 2 SP FP Administrative part fact 5 1 Administrative part main L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 R01 R11 R2 Administrative part fact 5 3 Administrative part fact 5 2 SP FP Administrative part fact 5 1 Administrative part main L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 R01 R11 R2 Administrative part fact 5 3 Administrative part fact 5 2 SP FP Administrative part fact 5 1 Administrative part main L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 R01 R11 R2 Administrative part fact 5 3 Administrative part fact 5 2 SP FP Administrative part main L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end
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L4: Load_Constant 1, R0 Branch L6.global _fact Add _Constant -K2, SP L3: Cmp_Constant R0, 0 Branch_Eq L4 Branch L5 R02 R13 R2 Administrative part fact 5 3 SP FP Administrative part main L5: Store_Local R0, 5(FP) Sub_Constant 1, R0 JSR _fact Load_Local 5(FP), R1 Mult_Reg R1, R0 Branch L6 L6: Add_Constant K2, SP RTS.end
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