switch_vs_if.c

#include <stdio.h>

int main(){
    int x, y;
    scanf("%d", &x);

    switch(x){
        case 1:  y = 7; break;
        case 2:  y = 1; break;
        case 3:  y = 3; break;
        default: y = 0;
    }
    
    printf("y = %d\n", y);
    
    if(x == 1){
        y = 7;
    } else if(x == 2){
        y = 1;
    } else if(x == 3){
        y = 3;
    } else {
        y = 0;
    }
    
    printf("y = %d\n", y);
    return 0;
}

// gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1)
/* gcc tst.c -O2 -o tst.s -S


	.file	"tst.c"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"%d"
.LC1:
	.string	"y = %d\n"
	.section	.text.startup,"ax",@progbits
	.p2align 4,,15
	.globl	main
	.type	main, @function
main:
.LFB11:
	.cfi_startproc
	subq	$24, %rsp
	.cfi_def_cfa_offset 32
	leaq	.LC0(%rip), %rdi
	xorl	%eax, %eax
	leaq	12(%rsp), %rsi
	call	__isoc99_scanf@PLT

	movl	12(%rsp), %eax
	xorl	%esi, %esi
	subl	$1, %eax
	cmpl	$2, %eax
	ja	.L2
	leaq	CSWTCH.2(%rip), %rdx
	movl	(%rdx,%rax,4), %esi
.L2:
	leaq	.LC1(%rip), %rdi
	xorl	%eax, %eax
	call	printf@PLT

	movl	12(%rsp), %esi
	cmpl	$1, %esi
	je	.L5
	cmpl	$2, %esi
	je	.L6
	cmpl	$3, %esi
	movl	$0, %eax
	cmovne	%eax, %esi
.L3:
	leaq	.LC1(%rip), %rdi
	xorl	%eax, %eax
	call	printf@PLT
	xorl	%eax, %eax
	addq	$24, %rsp
	.cfi_remember_state
	.cfi_def_cfa_offset 8
	ret
.L5:
	.cfi_restore_state
	movl	$7, %esi
	jmp	.L3
.L6:
	movl	$1, %esi
	jmp	.L3
	.cfi_endproc
.LFE11:
	.size	main, .-main
	.section	.rodata
	.align 8
	.type	CSWTCH.2, @object
	.size	CSWTCH.2, 12
CSWTCH.2:
	.long	7
	.long	1
	.long	3
	.ident	"GCC: (Debian 6.3.0-18+deb9u1) 6.3.0 20170516"
	.section	.note.GNU-stack,"",@progbits


*/