1 // 2 // Fibonnaci(recursive) function 3 // 4 5 /* -------------------------------------------------- 6 Define required labels for EGTAPI 7 -------------------------------------------------- */ 8 .global main, Stop, CodeEnd, DataStart, DataEnd 9 .global fib, k, result 10 11 /* -------------------------------------------------- 12 Begin of the program instructions 13 -------------------------------------------------- */ 14 .text 15 main: 16 17 // result = fib(k) 18 19 /* ------------------------------------------------- 20 Pass parameter k (using stack) 21 ------------------------------------------------- */ 22 0000 000000E3 movw r0, #:lower16:k 23 0004 000040E3 movt r0, #:upper16:k 24 0008 000090E5 ldr r0, [r0] 25 000c 04002DE5 push {r0} 26 27 /* ---------------------------------------------------------------- 28 call result = fib(k) 29 ---------------------------------------------------------------- */ 30 0010 FEFFFFEB bl fib 31 0014 04D08DE2 add sp, sp, #4 // Clean up the parameter k 32 33 /* ----------------------------------------------------------------- 34 Save return value (in r0) to variable result 35 ----------------------------------------------------------------- */ 36 0018 001000E3 movw r1, #:lower16:result // Do NOT use r0 !!! 37 001c 001040E3 movt r1, #:upper16:result // (Because r0 contains the return value) 38 39 0020 000081E5 str r0, [r1] // This will store return value in sum 40 41 Stop: 42 0024 0000A0E1 nop // Stop point of main( ) 43 44 45 46 47 48 /* ---------------------------------------------------------------- 49 Function int fib(int n) 50 51 Stack frame structure: 52 53 old FP <--------------------------------- FP 54 old LR (ret addr) 55 n +8 56 57 Body of fib(n) 58 59 if ( n == 0 ) 60 return 1; 61 if ( n == 1 ) 62 return 1; 63 else 64 return fib(n-1) + fib(n-2); 65 ---------------------------------------------------------------- */ 66 67 fib: 68 69 // When fib begins, we will have: n on the stack 70 71 72 /* ========================================================== 73 Function Prelude: complete the stack frame structure 74 ========================================================== */ 75 0028 04E02DE5 push {lr} // Save LR (return address) 76 002c 04B02DE5 push {fp} // Save FP (used by caller) 77 0030 0DB0A0E1 mov fp, sp // Mark the stack top location before 78 // allocating any local variables 79 0034 00D04DE2 sub sp, sp, #0 // Allocate 0 int variables on the stack 80 81 82 83 /* =============================================== 84 We completed the stack frame 85 Now we can write the function body 86 =============================================== */ 87 // if ( n == 0 ) 88 0038 08009BE5 ldr r0, [fp, #8] // r0 = n 89 90 003c 000050E3 cmp r0, #0 // Check n == 0 91 0040 0300001A bne else1 // n != 0 --> Goto "else1" part 92 93 // return 1 94 95 ///// put return value 1 in return location r0 96 0044 0100A0E3 mov r0, #1 97 98 /* ============================================================= 99 Function Postlude: de-allocate local variable and restore FP 100 ============================================================= */ 101 0048 0BD0A0E1 mov sp, fp // De-allocate local variables 102 004c 04B09DE4 pop {fp} // Restore fp 103 0050 04F09DE4 pop {pc} // Return to the caller 104 105 else1: 106 // if ( n == 1 ) 107 0054 08009BE5 ldr r0, [fp, #8] // r0 = n 108 109 0058 010050E3 cmp r0, #1 // Check n == 1 110 005c 0300001A bne else2 // n != 1 --> Goto "else2" part 111 112 // return 1 113 114 ///// put return value 1 in return location r0 115 0060 0100A0E3 mov r0, #1 116 117 /* ============================================================= 118 Function Postlude: de-allocate local variable and restore FP 119 ============================================================= */ 120 0064 0BD0A0E1 mov sp, fp // De-allocate local variables 121 0068 04B09DE4 pop {fp} // Restore fp 122 006c 04F09DE4 pop {pc} // Return to the caller 123 124 125 else2: 126 // Compute: fib(n-1) + fib(n-2) 127 128 //// Compute fib(n-1) first 129 0070 08009BE5 ldr r0, [fp, #8] // r0 = n 130 0074 010040E2 sub r0, r0, #1 // r0 = n-1 131 132 0078 04002DE5 push {r0} // pass (n-1) to fib on stack 133 007c FEFFFFEB bl fib 134 0080 04D08DE2 add sp, sp, #4 // Clean up parameter (n-1) from stack 135 136 //// ** Right now, r0 = fib(n-1) --- we can't lose this value !!! 137 //// ** But we can't compute fib(n-1) + fib(n-2) without fib(n-2) 138 //// ** We will call fib to compute fib(n-2) 139 //// ** We MUST save r0 on the STACK !!! 140 141 0084 04002DE5 push {r0} // Save fib(n-1) on the stack 142 143 //// Compute fib(n-2) 144 0088 08009BE5 ldr r0, [fp, #8] // r0 = n 145 008c 020040E2 sub r0, r0, #2 // r0 = n-2 146 147 0090 04002DE5 push {r0} // pass (n-2) to fib on stack 148 0094 FEFFFFEB bl fib 149 0098 04D08DE2 add sp, sp, #4 // Clean up parameter (n-2) from stack 150 151 //// ** Right now, r0 = fib(n-2) - we can now compute fib(n-1)+fib(n-2) 152 153 009c 04109DE4 pop {r1} // Retrieve fib(n-1) from the stack 154 155 00a0 000081E0 add r0, r1, r0 // r0 = fib(n-1) + fib(n-2) 156 // NOTE: r0 has the correct return value !!! 157 158 // return fib(n-1)+fib(n-2) in r0 159 /* ============================================================= 160 Function Postlude: de-allocate local variable and restore FP 161 ============================================================= */ 162 00a4 0BD0A0E1 mov sp, fp // De-allocate local variables 163 00a8 04B09DE4 pop {fp} // Restore fp 164 00ac 04F09DE4 pop {pc} // Return to the caller 165 166 167 168 169 CodeEnd: 170 00b0 0000A0E1 nop 171 172 /* -------------------------------------------------- 173 Begin of the permanent program variables 174 -------------------------------------------------- */ 175 .data 176 DataStart: 177 178 0000 03000000 k: .4byte 3 179 0004 00000000 result: .skip 4 180 181 DataEnd: 182 183 .end DEFINED SYMBOLS /home/cs255001/cs255/demo/8-sub/fib.s:15 .text:0000000000000000 main /home/cs255001/cs255/demo/8-sub/fib.s:41 .text:0000000000000024 Stop /home/cs255001/cs255/demo/8-sub/fib.s:169 .text:00000000000000b0 CodeEnd /home/cs255001/cs255/demo/8-sub/fib.s:176 .data:0000000000000000 DataStart /home/cs255001/cs255/demo/8-sub/fib.s:181 .data:0000000000000008 DataEnd /home/cs255001/cs255/demo/8-sub/fib.s:67 .text:0000000000000028 fib /home/cs255001/cs255/demo/8-sub/fib.s:178 .data:0000000000000000 k /home/cs255001/cs255/demo/8-sub/fib.s:179 .data:0000000000000004 result /home/cs255001/cs255/demo/8-sub/fib.s:22 .text:0000000000000000 $a /home/cs255001/cs255/demo/8-sub/fib.s:105 .text:0000000000000054 else1 /home/cs255001/cs255/demo/8-sub/fib.s:125 .text:0000000000000070 else2 /home/cs255001/cs255/demo/8-sub/fib.s:179 .data:0000000000000004 $d NO UNDEFINED SYMBOLS 1 2 .global malloc, print 3 .global stdout_start, stdout_end 4 5 // ********************************************** 6 // malloc: simulate memory allocate 7 // 8 // This function will NOT change ANY registers 9 // (I.e.: will preserve ALL registers) 10 // ********************************************** 11 malloc: 12 0000 0E002DE9 push {r1, r2, r3} // Save scratch registers 13 14 0004 001000E3 movw r1, #:lower16:maddr 15 0008 001040E3 movt r1, #:upper16:maddr // r1 = &maddr 16 000c 003091E5 ldr r3, [r1] // r3 = maddr 17 18 // -------------------------------------- 19 // Make new maddr (divisible by 8) 20 // -------------------------------------- 21 22 0010 002083E0 add r2, r3, r0 // New maddr 23 0014 082082E2 add r2, r2, #8 // Making sure it increase 24 25 0018 0700A0E3 mov r0, #0x7 // r0 = 0000..00111 26 001c 0000E0E1 mvn r0, r0 // r0 = 1111..11000 27 0020 002002E0 and r2, r2, r0 // Knock off the last 3 bits 28 0024 002081E5 str r2, [r1] // Update maddr 29 30 31 // -------------------------------------- 32 // Return to caller 33 // -------------------------------------- 34 0028 0300A0E1 mov r0, r3 // Return maddr value in r0 35 002c 0E00BDE8 pop {r1, r2, r3} // Restore scratch registers 36 0030 0EF0A0E1 mov pc, lr // Return 37 38 0034 00000400 maddr: .word 0x40000 // Start address of the heap 39 40 41 // ******************************************************************* 42 // print: simulate print output in Egtapi 43 // 44 // input: r0 = address of string 45 // r1 = # characters to write 46 // 47 // Egtapi will show ASCII data stored starting at stdout_start 48 // until stdout_end in its output area 49 // 50 // This function will NOT change ANY registers 51 // (I.e.: will preserve ALL registers) 52 // ******************************************************************* 53 print: 54 0038 1C002DE9 push {r2, r3, r4} // Save scratch registers 55 56 003c 002000E3 movw r2, #:lower16:stdout_end 57 0040 002040E3 movt r2, #:upper16:stdout_end // r2 = &stdout_end 58 0044 002092E5 ldr r2, [r2] // r2 = stdout_end 59 60 0048 0130A0E1 mov r3, r1 // r3 = # char to copy 61 62 printLoop: 63 004c 000053E3 cmp r3, #0 64 0050 0500000A beq printDone 65 66 0054 0040D0E5 ldrb r4, [r0] // Get next char 67 0058 0040C2E5 strb r4, [r2] // Write next char 68 69 005c 010080E2 add r0, r0, #1 70 0060 012082E2 add r2, r2, #1 71 72 0064 013043E2 sub r3, r3, #1 73 74 0068 F7FFFFEA b printLoop 75 76 printDone: 77 006c 2040A0E3 mov r4, #32 // Space 78 0070 0040C2E5 strb r4, [r2] 79 0074 012082E2 add r2, r2, #1 80 81 0078 003000E3 movw r3, #:lower16:stdout_end 82 007c 003040E3 movt r3, #:upper16:stdout_end // r2 = &stdout_end 83 0080 002083E5 str r2, [r3] 84 85 0084 1C00BDE8 pop {r2, r3, r4} // Restore scratch registers 86 0088 0EF0A0E1 mov pc, lr // Return 87 88 89 90 91 008c 00000500 stdout_start: .word 0x50000 // This value remains unchanged 92 0090 00000500 stdout_end: .word 0x50000 93 94 95 .end DEFINED SYMBOLS /home/egtapi/lib/cs255lib.s:11 .text:0000000000000000 malloc /home/egtapi/lib/cs255lib.s:53 .text:0000000000000038 print /home/egtapi/lib/cs255lib.s:91 .text:000000000000008c stdout_start /home/egtapi/lib/cs255lib.s:92 .text:0000000000000090 stdout_end /home/egtapi/lib/cs255lib.s:12 .text:0000000000000000 $a /home/egtapi/lib/cs255lib.s:38 .text:0000000000000034 maddr /home/egtapi/lib/cs255lib.s:38 .text:0000000000000034 $d /home/egtapi/lib/cs255lib.s:54 .text:0000000000000038 $a /home/egtapi/lib/cs255lib.s:62 .text:000000000000004c printLoop /home/egtapi/lib/cs255lib.s:76 .text:000000000000006c printDone /home/egtapi/lib/cs255lib.s:91 .text:000000000000008c $d NO UNDEFINED SYMBOLS