bl--case-switch.s

// ------------------------------------------------------
// Porting Raspberry Pi ARM code to Apple Silicon
// 2023-01-09
// Jds
// ------------------------------------------------------
// Implementing a Switch in ASM
//
// Change the values in the first line (MOV X2, 1) to
// get different results.
//
// COMPILE  -->  make main
// RUN      -->  ./filename ; echo $?
// ------------------------------------------------------


.global main
.align 4


main:
	MOV X2, 1						// Store 1 in X2
	CMP X2, 0						// Compare 0 with X2 (1)
	B.EQ case_0						// If equal, branch to case_0

	CMP X2, 1						// Compare 1 with X2 (1)
	B.EQ case_1						// If equal, branch to case_1

	BL case_def						// Else, branch to case_def (default)


case_0:
	ADRP	X0, output_0@PAGE		// load the string to print
	ADD	X0, X0, output_0@PAGEOFF
	BL end							// Branch to end


case_1:
	ADRP	X0, output_1@PAGE		// load the string to print
	ADD	X0, X0, output_1@PAGEOFF
	BL end							// Branch to end


case_def:
	ADRP	X0, output_def@PAGE		// load the string to print
	ADD	X0, X0, output_def@PAGEOFF  // No need to branch to end as we simply
									//   fall through.

end:
	BL	_printf						// print the loaded message
	mov	X16, 1						// System call to terminate this program
	svc	0



.data
output_0:   .asciz "Case 0 -- They are not equal.\n"
output_1:   .asciz "Case 1 -- They are equal.\n"
output_def: .asciz "Case 2 -- I have no idea.\n"