mirror of
https://github.com/autc04/Retro68.git
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64 lines
1.5 KiB
ArmAsm
64 lines
1.5 KiB
ArmAsm
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.text
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.global _start
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.type _start,@function
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.stabs "crt0.S",100,0,0,_start
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.stabs "int:t(0,1)=r(0,1);-32768;32767;",128,0,0,0
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.stabs "_start:F(0,1)",36,0,1,_start
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_start:
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; R14 always contains memory base address (0)
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ldi r14,0
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; Set the USER and SYSTEM stack pointers.
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ldi r0, 0 ; zero arguments
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ldi r1, 0
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mvtc r0, psw ; select SPI and set it
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ldi sp, _stack
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ldi r10, 0x8000 ; select SPU/FP and set it
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mvtc r10, psw || ldi r11, 0; clear stack frame
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ldi sp, _stack - 0x200
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ldi r13, 0
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; Clear the BSS. Do it in two parts for efficiency: longwords first
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; for most of it, then the remaining 0 to 3 bytes.
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ldi r2, __bss_start ; R2 = start of BSS
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ldi r3, _end ; R3 = end of BSS + 1
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sub r3, r2 ; R3 = BSS size in bytes
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mv r4, r3
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srli r4, 2 ; R4 = BSS size in longwords (rounded down)
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loop1:
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cmpeqi r4, 0 ; more longords to zero out?
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brf0t.s endloop1 ; nope
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st2w r0, @r2+ ; yep, zero out another longword
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subi r4, 1 ; decrement count
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bra.l loop1 ; go do some more
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endloop1:
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and3 r4, r3, 3 ; get no. of remaining BSS bytes to clear
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loop2:
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cmpeqi r4, 0 ; more bytes to zero out?
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brf0t.s endloop2 ; nope
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stb r0, @r2 ; yep, zero out another byte
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addi r2, 1 ; bump address
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subi r4, 1 ; decrement count
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bra.s loop2 ; go do some more
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endloop2:
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; Call main, then stop simulator
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st r11, @-sp
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st r13, @-sp
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mv r11, sp
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bl main
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bl exit
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stop
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.Lstart:
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.size _start,.Lstart-_start
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.stabs "",36,0,0,.Lstart-_start
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.section .stack
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_stack: .long 1
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