When is "greater than" really "greater than"

cis-lclient02:~/2012/quiz23>more maingt.c
#include <stdio.h>
int gt1(int a, int b);
int gt2(int a, int b);
main () {
   int twob = 2000000000;
   printf("%d\n", gt1(twob, -twob));
   printf("%d\n", gt2(twob, -twob));
}
int gt1(int a, int b) {
   if (a >= b)
      return 1;
   else
      return 0;
}
int gt2(int a, int b) {
   if (a - b >= 0)
      return 1;
   else
      return 0;
}
cis-lclient02:~/2012/quiz23>gcc maingt.c
cis-lclient02:~/2012/quiz23>./a.out
1
0
cis-lclient02:~/2012/quiz23>gcc -S maingt.c
cis-lclient02:~/2012/quiz23>more maingt.s
        .file   "maingt.c"
        .section        .rodata
.LC0:
        .string "%d\n"
        .text
.globl main
        .type   main, @function
main:
        pushl   %ebp
        movl    %esp, %ebp
        andl    $-16, %esp
        subl    $32, %esp
        movl    $2000000000, 28(%esp)
        movl    28(%esp), %eax
        negl    %eax
        movl    %eax, 4(%esp)
        movl    28(%esp), %eax
        movl    %eax, (%esp)
        call    gt1
        movl    $.LC0, %edx
        movl    %eax, 4(%esp)
        movl    %edx, (%esp)
        call    printf
        movl    28(%esp), %eax
        negl    %eax
        movl    %eax, 4(%esp)
        movl    28(%esp), %eax
        movl    %eax, (%esp)
        call    gt2
        movl    $.LC0, %edx
        movl    %eax, 4(%esp)
        movl    %edx, (%esp)
        call    printf
        leave
        ret
        .size   main, .-main
.globl gt1
        .type   gt1, @function
gt1:
        pushl   %ebp
        movl    %esp, %ebp
        movl    8(%ebp), %eax
        cmpl    12(%ebp), %eax
        jl      .L4
        movl    $1, %eax
        jmp     .L5
.L4:
        movl    $0, %eax
.L5:
        popl    %ebp
        ret
        .size   gt1, .-gt1
.globl gt2
        .type   gt2, @function
gt2:
        pushl   %ebp
        movl    %esp, %ebp
        movl    12(%ebp), %eax
        movl    8(%ebp), %edx
        movl    %edx, %ecx
        subl    %eax, %ecx
        movl    %ecx, %eax
        testl   %eax, %eax
        js      .L8
        movl    $1, %eax
        jmp     .L9
.L8:
        movl    $0, %eax
.L9:
        popl    %ebp
        ret
        .size   gt2, .-gt2
        .ident  "GCC: (GNU) 4.4.4 20100630 (Red Hat 4.4.4-10)"
        .section        .note.GNU-stack,"",@progbits
cis-lclient02:~/2012/quiz23>