"if (i == n) ++i;" or "i += i == n;"?

[Erik <sigra at home dot se>]

Suppose that we have a function f that can be written in 2 ways with 
identical result:
unsigned int f(unsigned int i, unsigned int n) {++i; if (i == n) ++i; 
return i;}
unsigned int f(unsigned int i, unsigned int n) {++i; i += i == n; return i;}

g++ -O3 produces different code for the 2 versions:
       pushl   %ebp
.LCFI0:
+       xorl    %edx, %edx
       movl    %esp, %ebp
.LCFI1:
-       movl    8(%ebp), %edx
-       leal    1(%edx), %eax
+       movl    8(%ebp), %eax
+       incl    %eax
       cmpl    12(%ebp), %eax
-       je      .L6
       popl    %ebp
-       ret
-       .p2align 4,,7
-.L6:
-       popl    %ebp
-       leal    2(%edx), %eax
+       sete    %dl
+       addl    %edx, %eax
       ret
.LFE2:

This implies that one of the following 3 statements holds:
1. The 2 versions of f are indeed not identical.
2. The 2 versions of the generated code are equally efficient, so the 
difference does not matter.
3. g++ generates suboptimal code for one of the versions of f.

Anyone knows which statement holds.