Compiler optimization of strcmp I don't understand, against a constant string

In order to improve my binary exploitation skills, and deepen my understanding in low level environments I tried solving challenges in pwnable.kr, The first challenge- called fd has the following C code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char buf[32];
int main(int argc, char* argv[], char* envp[]){
        if(argc<2){
                printf("pass argv[1] a number\n");
                return 0;
        }
        int fd = atoi( argv[1] ) - 0x1234;
        int len = 0;
        len = read(fd, buf, 32);
        if(!strcmp("LETMEWIN\n", buf)){
                printf("good job :)\n");
                system("/bin/cat flag");
                exit(0);
        }
        printf("learn about Linux file IO\n");
        return 0;

}

I used objdump -S -g ./fd in order to disassemble it, and I got confused, because insteaad of calling a strcmp function. It just compared the strings without calling it. This is the assembly code im talking about:

 80484c6:   e8 05 ff ff ff          call   80483d0 <atoi@plt> 
 80484cb:   2d 34 12 00 00          sub    eax,0x1234 
 ; eax = atoi( argv[1] ) - 0x1234;
 ; initialize fd=eax
 80484d0:   89 44 24 18             mov    DWORD PTR [esp+0x18],eax
 ; initialize len
 80484d4:   c7 44 24 1c 00 00 00    mov    DWORD PTR [esp+0x1c],0x0

 ; Set up read variables
 80484db:   00 
 80484dc:   c7 44 24 08 20 00 00    mov    DWORD PTR [esp+0x8],0x20 ; read 32 bytes
 80484e3:   00 
 80484e4:   c7 44 24 04 60 a0 04    mov    DWORD PTR [esp+0x4],0x804a060 ; buf variable address
 80484eb:   08 
 80484ec:   8b 44 24 18             mov    eax,DWORD PTR [esp+0x18]
 80484f0:   89 04 24                mov    DWORD PTR [esp],eax ; fd variable
 80484f3:   e8 78 fe ff ff          call   8048370 <read@plt> 

 80484f8:   89 44 24 1c             mov    DWORD PTR [esp+0x1c],eax
 80484fc:   ba 46 86 04 08          mov    edx,0x8048646 ; "LETMEWIN\n" address
 8048501:   b8 60 a0 04 08          mov    eax,0x804a060 ; buf address
 8048506:   b9 0a 00 00 00          mov    ecx,0xa ; what is this?
 ; strcmp starts here?
 804850b:   89 d6                   mov    esi,edx
 804850d:   89 c7                   mov    edi,eax
 804850f:   f3 a6                   repz cmps BYTE PTR ds:[esi],BYTE PTR es:[edi] ; <------- ?STRCMP?

The things I don't understand are:

1. Where is the strcmp call? And why is it like that?
2. What does this 8048506: b9 0a 00 00 00 mov ecx,0xa do?