Why are compilers so stupid?

int x = 0;
for (int i = 0; i < 100 * 1000 * 1000 * 1000; ++i) {
    x += x + x + x + x + x;
}
System.out.println(x);

public int slow() {
    String s = "x";
    for (int i = 0; i < 100000; ++i) {
        s += "x";
    }
    return 10;
}

#include <stdio.h>  /* printf() */

int factorial(int n) {
   return n == 0 ? 1 : n * factorial(n - 1);
}

int main() {
   int n = 10;

   printf("factorial(%d) = %dn", n, factorial(n));

   return 0;
}

factorial:
   .LFB13:
           testl   %edi, %edi
           movl    $1, %eax
           je  .L3
           .p2align 4,,10
           .p2align 3
   .L4:
           imull   %edi, %eax
           subl    $1, %edi
           jne .L4
   .L3:
           rep
           ret

main:
   .LFB14:
           subq    $8, %rsp
   .LCFI0:
           movl    $3628800, %edx
           movl    $10, %esi
           movl    $.LC0, %edi
           xorl    %eax, %eax
           call    printf
           xorl    %eax, %eax
           addq    $8, %rsp
           ret

x = 0
sleep 6 // Let's assume this is defined somewhere.
print x

int x = 1;
int y = 1;
int z = x - y;
for (int i = 0; i < 100 * 1000 * 1000 * 1000; ++i) {
    z += z + z + z + z + z;
}
System.out.println(z);

extern int x; // defined elsewhere
for (int i = 0; i < 100 * 1000 * 1000 * 1000; ++i) {
    x += x + x + x + x + x;
}
return x;

extern volatile int x; // defined elsewhere
for (int i = 0; i < 100 * 1000 * 1000 * 1000; ++i) {
    x += x + x + x + x + x;
}
return x;

[js@HOST2 java]$ gcj --main=Optimize -O2 Optimize.java
[js@HOST2 java]$ ./a.out
0
[js@HOST2 java]$

class Optimize {
    private static int doIt() {
        int x = 0;
        for (int i = 0; i < 100 * 1000 * 1000 * 1000; ++i) {
            x += x + x + x + x + x;
        }
        return x;
    }
    public static void main(String[] args) {
        for(int i=0;i<5;i++) {
            doIt();
        }
    }
}

1       java.lang.String::hashCode (60 bytes)
1%      Optimize::doIt @ 4 (30 bytes)
2       Optimize::doIt (30 bytes)

"starting windows"
"enjoy freecell/solitaire"
"shutting down windows"

#include <stdio.h>
int main()
{
    int x = 0;
    for (int i = 0; i < 100 * 1000 * 1000 * 1000; ++i) {
        x += x + x + x + x + x;
    }
    printf("%d", x);
}