New version of the effect of optimization,  made in 2008
See the difference from the older version.

----------------
Case 1 new   
----------------
main()
{
  int i;

  for(i=1;i<=2;i++){printf("test out\n"); }
  printf("end\n");
}
-----------------------
  -O0 -S
-------------------

	.file	"test-opt.c"
	.section	.rodata
.LC0:
	.string	"test out\n"
.LC1:
	.string	"end\n"
	.text
	.p2align 2,,3
.globl main
	.type	main, @function
main:
	pushl	%ebp
	movl	%esp, %ebp
	subl	$8, %esp
	andl	$-16, %esp
	movl	$0, %eax
	addl	$15, %eax
	addl	$15, %eax
	shrl	$4, %eax
	sall	$4, %eax
	subl	%eax, %esp
	movl	$1, -4(%ebp)
.L2:
	cmpl	$2, -4(%ebp)
	jg	.L3
	subl	$12, %esp
	pushl	$.LC0
	call	printf
	addl	$16, %esp
	leal	-4(%ebp), %eax
	incl	(%eax)
	jmp	.L2
.L3:
	subl	$12, %esp
	pushl	$.LC1
	call	printf
	addl	$16, %esp
	leave
	ret
	.size	main, .-main
	.ident	"GCC: (GNU) 3.4.6 [FreeBSD] 20060305"

-----------------------
  -O3 -S
-------------------
	.file	"test-opt.c"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"test out"
.LC1:
	.string	"end"
	.text
	.p2align 2,,3
.globl main
	.type	main, @function
main:
	pushl	%ebp
	movl	%esp, %ebp
	pushl	%ebx
	pushl	%eax
	andl	$-16, %esp
	subl	$16, %esp
	movl	$1, %ebx
.L5:
	subl	$12, %esp
	pushl	$.LC0
	call	puts
	addl	$16, %esp
	decl	%ebx
	jns	.L5
	subl	$12, %esp
	pushl	$.LC1
	call	puts
	movl	-4(%ebp), %ebx
	leave
	ret
	.size	main, .-main
	.ident	"GCC: (GNU) 3.4.6 [FreeBSD] 20060305"

----------------------
  -Os  -S   minimum memory
---------------------
	.file	"test-opt.c"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"test out"
.LC1:
	.string	"end"
	.text
.globl main
	.type	main, @function
main:
	pushl	%ebp
	movl	%esp, %ebp
	pushl	%ebx
	movl	$1, %ebx
.L5:
	pushl	$.LC0
	call	puts
	decl	%ebx
	popl	%eax
	jns	.L5
	pushl	$.LC1
	call	puts
	movl	-4(%ebp), %ebx
	leave
	ret
	.size	main, .-main
	.ident	"GCC: (GNU) 3.4.6 [FreeBSD] 20060305"

------------------------------------------------------
-----------------------------------------------------

Case 2 new   
----------------
main()
{
  int i,x;

  i=2;
  x=1+i;
  printf("result=%d\n",x);
}
-------------
 -O0  -S
-----
	.file	"test-opt2.c"
	.section	.rodata
.LC0:
	.string	"result=%d\n"
	.text
	.p2align 2,,3
.globl main
	.type	main, @function
main:
	pushl	%ebp
	movl	%esp, %ebp
	subl	$8, %esp
	andl	$-16, %esp
	movl	$0, %eax
	addl	$15, %eax
	addl	$15, %eax
	shrl	$4, %eax
	sall	$4, %eax
	subl	%eax, %esp
	movl	$2, -4(%ebp)
	movl	-4(%ebp), %eax
	incl	%eax
	movl	%eax, -8(%ebp)
	subl	$8, %esp
	pushl	-8(%ebp)
	pushl	$.LC0
	call	printf
	addl	$16, %esp
	leave
	ret
	.size	main, .-main
	.ident	"GCC: (GNU) 3.4.6 [FreeBSD] 20060305"


-------------
 -O3  -S
-----
	.file	"test-opt2.c"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"result=%d\n"
	.text
	.p2align 2,,3
.globl main
	.type	main, @function
main:
	pushl	%ebp
	movl	%esp, %ebp
	subl	$8, %esp
	andl	$-16, %esp
	subl	$24, %esp
	pushl	$3
	pushl	$.LC0
	call	printf
	leave
	ret
	.size	main, .-main
	.ident	"GCC: (GNU) 3.4.6 [FreeBSD] 20060305"
-------------
 -Os  -S
-----
	.file	"test-opt2.c"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"result=%d\n"
	.text
.globl main
	.type	main, @function
main:
	pushl	%ebp
	movl	%esp, %ebp
	pushl	$3
	pushl	$.LC0
	call	printf
	leave
	ret
	.size	main, .-main
	.ident	"GCC: (GNU) 3.4.6 [FreeBSD] 20060305"

------------------------------------------------
Case 3
-------------------------------------------------

main()
{
  long i,x;
  x=0;
  for(i=1;i<100000000;i++){x=x+i; }
  printf("result=%d\n",x);
}
-------------------------------------------
inoue@kir.ics.es.osaka-u.ac.jp% gcc test-opt1.c

inoue@kir.ics.es.osaka-u.ac.jp% time a.out

result=887459712

0.382u 0.000s 0:00.38 100.0%    5+180k 0+0io 0pf+0w

inoue@kir.ics.es.osaka-u.ac.jp% gcc -O3 test-opt1.c

inoue@kir.ics.es.osaka-u.ac.jp% time a.out

result=887459712

0.057u 0.000s 0:00.05 100.0%    5+184k 0+0io 0pf+0w

inoue@kir.ics.es.osaka-u.ac.jp%