/* --------------------------------------------------------------
   Program file used to demo

	(1) Pass by value (a.k.a.: pass by copy)
	(2) Pass by reference
   -------------------------------------------------------------- */

        .global main, Stop, CodeEnd, DataStart, DataEnd

        .global f, k

/* --------------------------------------------------
   Begin of the program instructions
   -------------------------------------------------- */
        .text
main:
        /* =========================================
           Pass k to f( )     by value or by ref
           ========================================= */
	// Pass k  by value
	movw r0, #:lower16:k
	movt r0, #:upper16:k	// r0 = addr of var k
	push {r0}

	bl   f
	add  sp, sp, #4


Stop:
        nop


/* ================================================
   Function f that gets a parameter 

   Stack frame of f( ):

	  FP-->	+-----------+
        	|  old FP   |   FP + 0
		+-----------+
        	|  ret addr |   FP + 4
		+-----------+
        	|  param a  |   FP + 8
		+-----------+
   ================================================ */
f:
        /* ****************************************
           Prelude: build stack frame
           **************************************** */
        push	{lr}	        // Save return address in LR
        push	{fp}	        // Save Frame Pointer in FP
        mov	fp, sp	        // Initialize my own FP
        sub	sp, sp, #0      // I create 0 local variable in stack

	/* =======================================
	   F() executes:    a = a + 1  
	   ======================================= */
	ldr r0, [fp,#8]		// r0 = addr of the param
	ldr r1, [r0]		// r1 = value of the param
	add r1, r1, #1
	str r1, [r0]

        /* ************************************************
           Postlude: break down stack frame
           ************************************************ */
        mov	sp, fp		// De-allocate the local variables
        pop	{fp}		// Restore old FP
        pop	{pc}		// Return




CodeEnd:
        nop

/* --------------------------------------------------
   Begin of the permanent program variables
   -------------------------------------------------- */
        .data
DataStart:

k:	.4byte	7

DataEnd:

        .end