/* ------------------------------------------------------------------------
   Show how to access parameters and local variables in the program stack
   ------------------------------------------------------------------------ */

        .global main, Stop, CodeEnd, DataStart, DataEnd

	.global A

/* --------------------------------------------------
   Begin of the program instructions
   -------------------------------------------------- */
	.text
main:
       	mov   r0, #2222    // Pass 2222 as parameter 2 on stack
	push  {r0}

       	mov   r0, #1111    // Pass 1111 as parameter 1 on stack
	push  {r0}

       	bl    A            // Call function A             
	add   sp, sp, #8   // Clean up parameters on the stack

       	// When A returns, you will see the return value in r0 = 9999      
       	nop      
       	nop
Stop:
	nop


/* =================================================
   Method A store params and local vars in stack
   ================================================= */
A:
       	// When run in EGTAPI - you will see {1111, 2222} on stack

	/* ****************************************
	   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, #12     // I create 3 local variable in stack

       	// How to to access parameters and local variables
	// stored in the program stack

	ldr	r0, [fp, #8]    // Get parameter 1 = 1111
	str	r0, [fp, #-12]	// Store in local variable 1
	ldr	r1, [fp, #12]   // Get parameter 2 = 2222
	str	r1, [fp, #-8]	// Store in local variable 2
	add	r0, r0, r1
	str	r0, [fp, #-4]	// Store sum in local variable 3
	

        /* =================================================
	   We can use a register to return the return value
	   ================================================= */
       	mov   r0, #9999         // Pass return value in register r0  

       	/* ************************************************
	   Postlude: break down stack frame
	   ************************************************ */
	mov	sp, fp
	pop	{fp}

	pop	{pc}		// Return


CodeEnd:
    	nop

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

DataEnd:

	.end