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hello.ms revision 1.1 
      1 # output(): Hello, world.\n
      2 # mach(): all
      3 
      4 # Emit hello world while switching back and forth between arm/thumb.
      5 # ??? Unfinished
      6 
      7 	.macro invalid
      8 # This is "undefined" but it's not properly decoded yet.
      9 	.word 0x07ffffff
     10 # This is stc which isn't recognized yet.
     11 	stc 0,cr0,[r0]
     12 	.endm
     13 
     14 	.global _start
     15 _start:
     16 # Run some simple insns to confirm the engine is at least working.
     17 	nop
     18 
     19 # Skip over output text.
     20 
     21 	bl skip_output
     22 
     23 hello_text:
     24 	.asciz "Hello, world.\n"
     25 
     26 	.p2align 2
     27 skip_output:
     28 
     29 # Prime loop.
     30 
     31 	mov r4, r14
     32 
     33 output_next:
     34 
     35 # Switch arm->thumb to output next chacter.
     36 # At this point r4 must point to the next character to output.
     37 
     38 	adr r0, into_thumb + 1
     39 	bx r0
     40 
     41 into_thumb:
     42 	.thumb
     43 
     44 # Output a character.
     45 
     46 	mov r0,#3 @ writec angel call
     47 	mov r1,r4
     48 	swi 0xab @ ??? Confirm number.
     49 
     50 # Switch thumb->arm.
     51 
     52 	adr r5, back_to_arm
     53 	bx r5
     54 
     55 	.p2align 2
     56 back_to_arm:
     57 	.arm
     58 
     59 # Load next character, see if done.
     60 
     61 	add r4,r4,#1
     62 	sub r3,r3,r3
     63 	ldrb r5,[r4,r3]
     64 	teq r5,#0
     65 	beq done
     66 
     67 # Output a character (in arm mode).
     68 
     69 	mov r0,#3
     70 	mov r1,r4
     71 	swi #0x123456
     72 
     73 # Load next character, see if done.
     74 
     75 	add r4,r4,#1
     76 	sub r3,r3,r3
     77 	ldrb r5,[r4,r3]
     78 	teq r5,#0
     79 	bne output_next
     80 
     81 done:
     82 	mov r0,#0x18
     83 	ldr r1,exit_code
     84 	swi #0x123456
     85 
     86 # If that fails, try to die with an invalid insn.
     87 
     88 	invalid
     89 
     90 exit_code:
     91 	.word 0x20026
     92