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A trivial prototype for clearing strings

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Jeremiah Orians 2016-08-14 16:06:12 -04:00
parent 5efaead1b0
commit 8a279ecc96
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Library function prototypes/clear_string.s Normal file
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# We will be using R0 and R1 to pass values to the function
# R15 will be used as the stack pointer
:start
LOADUI R0 @string
LOADUI R1 22
LOADUI R2 33
LOADUI R3 44
LOADUI R4 55
LOADUI R15 0x600
CALLI R15 @clear_string
HALT
:string
HALT
HALT
NOP
;; Our simple string compare function
:clear_string
;; Preserve registers
PUSHR R0 R15
PUSHR R1 R15
PUSHR R2 R15
PUSHR R3 R15
;; Setup registers
MOVE R1 R0
LOADUI R2 0
LOADUI R3 0
:clear_byte
LOADXU8 R0 R1 R2 ; Get the byte
STOREX8 R3 R1 R2 ; Overwrite with a Zero
ADDUI R2 R2 1 ; Prep for next loop
CMPJUMP.NE R0 R3 @clear_byte ; Stop if byte is NULL
;; Done
;; Restore registers
POPR R3 R15
POPR R2 R15
POPR R1 R15
POPR R0 R15
RET R15