loop_comparison.c

#include <stdio.h>

void loop_up() {
    int i;
    for (i = 0; i < 42; ++i) {
        printf("Hello");
    }
}

void loop_down() {
    int i;
    for (i = 42; i; --i) {
        printf("Hello");
    }
}
/* using sdcc version 3.6.0
 * (http://sdcc.sourceforge.net/) with 8051 target:
 * command line: sdcc -S --std-sdcc99 -mmcs51 --opt-code-speed loop_comparison.c
 */
  
/* resulting assembly (partial): */
/*
;------------------------------------------------------------
;	loop_comparison.c:3: void loop_up() {
;	-----------------------------------------
;	 function loop_up
;	-----------------------------------------
_loop_up:
	ar7 = 0x07
	ar6 = 0x06
	ar5 = 0x05
	ar4 = 0x04
	ar3 = 0x03
	ar2 = 0x02
	ar1 = 0x01
	ar0 = 0x00
;	loop_comparison.c:5: for (i = 0; i < 42; ++i) {
	mov	r6,#0x00
	mov	r7,#0x00
00102$:
;	loop_comparison.c:6: printf("Hello");
	push	ar7
	push	ar6
	mov	a,#___str_0
	push	acc
	mov	a,#(___str_0 >> 8)
	push	acc
	mov	a,#0x80
	push	acc
	lcall	_printf
	dec	sp
	dec	sp
	dec	sp
	pop	ar6
	pop	ar7
;	loop_comparison.c:5: for (i = 0; i < 42; ++i) {
	inc	r6
	cjne	r6,#0x00,00110$
	inc	r7
00110$:
	clr	c
	mov	a,r6
	subb	a,#0x2a
	mov	a,r7
	xrl	a,#0x80
	subb	a,#0x80
	jc	00102$
	ret
;------------------------------------------------------------
;Allocation info for local variables in function 'loop_down'
;------------------------------------------------------------
;i                         Allocated to registers r6 r7 
;------------------------------------------------------------
;	loop_comparison.c:10: void loop_down() {
;	-----------------------------------------
;	 function loop_down
;	-----------------------------------------
_loop_down:
;	loop_comparison.c:12: for (i = 42; i; --i) {
	mov	r6,#0x2a
	mov	r7,#0x00
00102$:
;	loop_comparison.c:13: printf("Hello");
	push	ar7
	push	ar6
	mov	a,#___str_0
	push	acc
	mov	a,#(___str_0 >> 8)
	push	acc
	mov	a,#0x80
	push	acc
	lcall	_printf
	dec	sp
	dec	sp
	dec	sp
	pop	ar6
	pop	ar7
;	loop_comparison.c:12: for (i = 42; i; --i) {
	mov	a,r6
	add	a,#0xff
	mov	r4,a
	mov	a,r7
	addc	a,#0xff
	mov	r5,a
	mov	ar6,r4
	mov	ar7,r5
	mov	a,r4
	orl	a,r5
	jnz	00102$
	ret
*/