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