Computer Engineering

AREA my_fancy_asm_code, CODE, READONLY ; Define the program area ; Export functions defined in this file. These functions need to be declared ; in the file calling them. EXPORT task10 EXPORT task11 EXPORT task12 EXPORT task13 EXPORT task14 EXPORT task15 IMPORT gPtrArray10a IMPORT gPtrArray11a IMPORT gPtrArray12a IMPORT gPtrArray13a IMPORT gPtrArray14a IMPORT gPtrArray15a IMPORT gVar1 ALIGN ; Align the data in the boundary of 4 bytes. task10 PROC LDR r0, =gPtrArray10a ; Loading the address of the global variable gPtrArray10a LDR r0, [r0] ; Loading the content of the global variable gPtrArray10a LDR r1, =gVar1 ; Loading the address of the global variable gVar1 LDR r1, [r1] ; Loading the content of the global variable gVar1 MOV r2, #0 ; variable (int) i task10_loop CMP r2, r1 ; test = r2 - r1 BGE task10_end ; if test >= 0, then branch to task10_end MOV r3, r2, LSL #2 ; r3 <- r2 * 4 SUB r3, #15 ; r3 <- r3 - 15 STRB r3, [r0, r2] ; r3 -> mem[r0 + r2] or r3 -> mem[r0 + i] ADD r2, #1 ; r2 <- r2 + 1 B task10_loop ; branch to task10_loop task10_end BX lr ; return ENDP ; If you need to use registers starting from r4, you need to PUSH them first to save the ; run-time environment for the caller. You need to POP them up at the exit of the code. task11 PROC BX lr ENDP task12 PROC PUSH {r4-r5, lr} LDR r0, =gPtrArray10a LDR r0, [r0] LDR r4, =gPtrArray12a LDR r4, [r4] LDR r1, =gVar1 LDR r1, [r1] MOV r2, #0 task12_loop CMP r2, r1 BGE task12_end LDRSB r3, [r0, r2] LDR r5, =10 SUB r5, r3 STRH r5, [r4, r2, LSL #1] ADD r3, #1 STRB r3, [r0, r2] ADD r2, #1 B task12_loop task12_end POP {r4-r5, pc} ; Pop lr to pc, which is the same as BX lr. ENDP task13 PROC PUSH {r4-r5, lr} POP {r4-r5, pc} ENDP task14 PROC PUSH {r4-r5, lr} LDR r0, =gPtrArray12a LDR r0, [r0] LDR r4, =gPtrArray14a LDR r4, [r4] LDR r1, =gVar1 LDR r1, [r1] SUB r1, #1 MOV r2, #0 task14_loop CMP r2, r1 BGE task14_end LDRSH r3, [r0] LDRSH r5, [r0, #2]! ADD r3, r5, LSL #3 STR r3, [r4, r2, LSL #2] ADD r2, #1 B task14_loop task14_end POP {r4-r5, pc} ENDP task15 PROC PUSH {r4-r5, lr} POP {r4-r5, pc} ENDP END