addition.pio

;
; Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
;
; SPDX-License-Identifier: BSD-3-Clause
;

.program addition

; Pop two 32 bit integers from the TX FIFO, add them together, and push the
; result to the TX FIFO. Autopush/pull should be disabled as we're using
; explicit push and pull instructions.
;
; This program uses the two's complement identity x + y == ~(~x - y)

	pull
	mov x, ~osr
	pull
	mov y, osr
	jmp test        ; this loop is equivalent to the following C code:
incr:               ; while (y--)
	jmp x-- test    ;     x--;
test:               ; This has the effect of subtracting y from x, eventually.
	jmp y-- incr
	mov isr, ~x
	push

% c-sdk {
static inline void addition_program_init(PIO pio, uint sm, uint offset) {
	pio_sm_config c = addition_program_get_default_config(offset);
	pio_sm_init(pio, sm, offset, &c);
	pio_sm_set_enabled(pio, sm, true);
}
%}