C ternary operator hack

gistfile1.sh

gcc -S -O2 ternary.c -o ternary.s
gcc -S -O2 ifelse.c -o ifelse.s

ifelse.c

#include <stdio.h>
#include <stdlib.h>

void fn(int c) {
  int x = 0, y = 0, v = 7;
  if (c) {
    x = v;
  } else {
    y = v;
  }
  printf("x: %d\ty: %d\n", x, y);
}

int main(int argc, char* argv[]) {
  if (argc != 2)
    return -1;
  fn(atoi(argv[1]));
  return 0;
}

ifelse.s

	.file	"ifelse.c"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"x: %d\ty: %d\n"
	.text
	.p2align 4,,15
	.globl	fn
	.type	fn, @function
fn:
.LFB34:
	.cfi_startproc
	cmpl	$1, %edi
	movl	$.LC0, %esi
	sbbl	%ecx, %ecx
	andl	$7, %ecx
	cmpl	$1, %edi
	movl	$1, %edi
	sbbl	%edx, %edx
	xorl	%eax, %eax
	notl	%edx
	andl	$7, %edx
	jmp	__printf_chk
	.cfi_endproc
.LFE34:
	.size	fn, .-fn
	.section	.text.startup,"ax",@progbits
	.p2align 4,,15
	.globl	main
	.type	main, @function
main:
.LFB35:
	.cfi_startproc
	subq	$8, %rsp
	.cfi_def_cfa_offset 16
	cmpl	$2, %edi
	movl	$-1, %eax
	jne	.L5
	movq	8(%rsi), %rdi
	movl	$10, %edx
	xorl	%esi, %esi
	call	strtol
	movl	%eax, %edi
	call	fn
	xorl	%eax, %eax
.L5:
	addq	$8, %rsp
	.cfi_def_cfa_offset 8
	ret
	.cfi_endproc
.LFE35:
	.size	main, .-main
	.ident	"GCC: (Ubuntu/Linaro 4.6.2-10ubuntu1) 4.6.2"
	.section	.note.GNU-stack,"",@progbits

ternary.c

#include <stdio.h>
#include <stdlib.h>

void fn(int c) {
  int x = 0, y = 0, v = 7;
  *(c ? &x : &y) = v;
  printf("x: %d\ty: %d\n", x, y);
}

int main(int argc, char* argv[]) {
  if (argc != 2)
    return -1;
  fn(atoi(argv[1]));
  return 0;
}

ternary.s

	.file	"ternary.c"
	.section	.rodata.str1.1,"aMS",@progbits,1
.LC0:
	.string	"x: %d\ty: %d\n"
	.text
	.p2align 4,,15
	.globl	fn
	.type	fn, @function
fn:
.LFB34:
	.cfi_startproc
	leaq	-12(%rsp), %rdx
	leaq	-16(%rsp), %rax
	testl	%edi, %edi
	movl	$0, -16(%rsp)
	movl	$0, -12(%rsp)
	movl	$.LC0, %esi
	cmove	%rdx, %rax
	movl	$1, %edi
	movl	$7, (%rax)
	movl	-12(%rsp), %ecx
	xorl	%eax, %eax
	movl	-16(%rsp), %edx
	jmp	__printf_chk
	.cfi_endproc
.LFE34:
	.size	fn, .-fn
	.section	.text.startup,"ax",@progbits
	.p2align 4,,15
	.globl	main
	.type	main, @function
main:
.LFB35:
	.cfi_startproc
	subq	$8, %rsp
	.cfi_def_cfa_offset 16
	cmpl	$2, %edi
	movl	$-1, %eax
	jne	.L5
	movq	8(%rsi), %rdi
	movl	$10, %edx
	xorl	%esi, %esi
	call	strtol
	movl	%eax, %edi
	call	fn
	xorl	%eax, %eax
.L5:
	addq	$8, %rsp
	.cfi_def_cfa_offset 8
	ret
	.cfi_endproc
.LFE35:
	.size	main, .-main
	.ident	"GCC: (Ubuntu/Linaro 4.6.2-10ubuntu1) 4.6.2"
	.section	.note.GNU-stack,"",@progbits