Arm/ifthen

You are designing a machine to serve food at a cafeteria. Each customer's order is represented by a 5-bit number, where each bit represents whether the order contains Apples, Bananas, Cherries, Dates, or Edamame (from least significant to most significant bit).

You are provided 6 functions:

add_a, add_b, add_c, add_d, and add_e: Add one of the foods to the plate
done: Call this when the entire plate is finished

These functions have no parameters and no return values. To make this problem easier, these functions do not clobber any registers.

Write a function that will assemble a plate. For each item that was ordered, call the appropriate function (add_a, add_b, add_c, add_d, and add_e), and then call done after all requested items have been added to the plate.

void build (int order);

It is possible to request an empty plate (in which case, only done will be called).

To encourage you to write an if-then structure with a minimum of duplicate code, don't call each function from more than one place in your code (only one call site for each function).

Expected solution length: Around 20 lines.

Sample Input

r0=5

Sample Output

add_a, add_c, and done are called

// You may uncomment these during testing
// add_a: ret
// add_b: ret
// add_c: ret
// add_d: ret
// add_e: ret
// done: ret

.global _start
_start:
	ldr r0, =5    // First function parameter is always passed through r0.
	bl build
	1: b 1b    // Done

build:
	// Because there are nested function calls, lr needs to be saved and restored.
	push {lr}

	// Your code here

	// ARM: Return by popping lr directly into pc
	pop {pc}

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arm/ifthen

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Arm/ifthen

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