stackoverflow-9767686-ARM-as

# Compares two methods of testing bit 5
# Clarify compiler behaviour for stackoverflow.com topic 9767686
# Created by G Bulmer on 19/03/2012.


main.o:     file format elf32-littlearm


Disassembly of section .text.main:

00000000 <main>:
#include "dummy_printf.h"	// get rid of stdio.h

#include "original_bit5.h"
#include "my_bit5.h"

int main (int argc, const char * argv[]) {
   0:	b508      	push	{r3, lr}
    int number = 16;

	original_bit5(number);
   2:	2010      	movs	r0, #16
   4:	f7ff fffe 	bl	0 <original_bit5>

	my_bit5(number);
   8:	2010      	movs	r0, #16
   a:	f7ff fffe 	bl	0 <my_bit5>

    return 0;
}
   e:	2000      	movs	r0, #0
  10:	bd08      	pop	{r3, pc}
  12:	bf00      	nop

original_bit5.o:     file format elf32-littlearm


Disassembly of section .text.original_bit5:

00000000 <original_bit5>:
#include "original_bit5.h"

void original_bit5(int number) {
	int mask = 1<<5;

	if ((number & mask) == 0)
   0:	f010 0f20 	tst.w	r0, #32
   4:	d005      	beq.n	1a <original_bit5+0x1a>
		dummy_printf("Bit is off");
	else
		dummy_printf("its on");
   6:	f240 0000 	movw	r0, #0
   a:	f2c0 0000 	movt	r0, #0
   e:	f7ff bffe 	b.w	0 <dummy_printf>

void original_bit5(int number) {
	int mask = 1<<5;

	if ((number & mask) == 0)
		dummy_printf("Bit is off");
  12:	f240 0000 	movw	r0, #0
  16:	f2c0 0000 	movt	r0, #0
  1a:	f7ff bffe 	b.w	0 <dummy_printf>
  1e:	bf00      	nop

my_bit5.o:     file format elf32-littlearm


Disassembly of section .text.my_bit5:

00000000 <my_bit5>:
#include "dummy_printf.h"	// get rid of stdio.h

#include "my_bit5.h"

void my_bit5(int number) {
	dummy_printf((number & 0x20)?"its on":"Bit is off");
   0:	f240 0200 	movw	r2, #0
   4:	f240 0300 	movw	r3, #0
   8:	f010 0f20 	tst.w	r0, #32
   c:	f2c0 0200 	movt	r2, #0
  10:	f2c0 0300 	movt	r3, #0
  14:	bf14      	ite	ne
  16:	4610      	movne	r0, r2
  18:	4618      	moveq	r0, r3
  1a:	f7ff bffe 	b.w	0 <dummy_printf>
  1e:	bf00      	nop