40 lines
882 B
ArmAsm
40 lines
882 B
ArmAsm
# We will be using R0 and R1 to pass values to the function
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# R15 will be used as the stack pointer
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:start
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LOADUI R0 @string
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COPY R1 R0
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LOADUI R2 33
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LOADUI R3 44
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LOADUI R4 55
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LOADUI R15 0x600
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CALLI R15 @strcmp
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HALT
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:string
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HALT
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NOP
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;; Our simple string compare function
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:strcmp
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;; Preserve registers
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PUSHR R2 R15
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PUSHR R3 R15
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PUSHR R4 R15
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;; Setup registers
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MOVE R2 R0
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MOVE R3 R1
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LOADUI R4 0
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:cmpbyte
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LOADXU8 R0 R2 R4 ; Get a byte of our first string
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LOADXU8 R1 R3 R4 ; Get a byte of our second string
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ADDUI R4 R4 1 ; Prep for next loop
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CMP R1 R0 R1 ; Compare the bytes
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CMPSKIPI.E R0 0 ; Stop if byte is NULL
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JUMP.E R1 @cmpbyte ; Loop if bytes are equal
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;; Done
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MOVE R0 R1 ; Prepare for return
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;; Restore registers
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POPR R4 R15
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POPR R3 R15
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POPR R2 R15
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RET R15
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