c2nasm gcc optimization compare (I)

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

int main(){

	return 0;
}

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c2nasm
gcc(7.3.0)
gcc -m64 -O3
--------------

default rel

global main

SECTION .text

SECTION .data

SECTION .bss

SECTION .text.startup

main:
        xor     eax, eax
        ret

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c2nasm
gcc(7.3.0)
gcc -m64 -O0
--------------

default rel

global main

SECTION .text

main:
        push    rbp
        mov     rbp, rsp
        mov     eax, 0
        pop     rbp
        ret

SECTION .data

SECTION .bss