With -O2

    .file   "main.c"
    .text
    .p2align 4,,15
    .globl  _xorBuffer
    .def    _xorBuffer; .scl    2;  .type   32; .endef
_xorBuffer:
LFB18:
    .cfi_startproc
    pushl   %esi
    .cfi_def_cfa_offset 8
    .cfi_offset 6, -8
    pushl   %ebx
    .cfi_def_cfa_offset 12
    .cfi_offset 3, -12
    movl    20(%esp), %edx
    movl    12(%esp), %ecx
    movl    16(%esp), %esi
    testl   %edx, %edx
    je  L1
    xorl    %eax, %eax
    .p2align 4,,10
L3:
    movzbl  (%esi,%eax), %ebx
    xorb    %bl, (%ecx,%eax)
    addl    $1, %eax
    subl    $1, %edx
    jne L3
L1:
    popl    %ebx
    .cfi_def_cfa_offset 8
    .cfi_restore 3
    popl    %esi
    .cfi_def_cfa_offset 4
    .cfi_restore 6
    ret
    .cfi_endproc
LFE18:
    .def    ___main;    .scl    2;  .type   32; .endef
    .section .rdata,"dr"
LC0:
    .ascii "result = \0"
LC1:
    .ascii "%.2x\0"
    .section    .text.startup,"x"
    .p2align 4,,15
    .globl  _main
    .def    _main;  .scl    2;  .type   32; .endef
_main:
LFB19:
    .cfi_startproc
    pushl   %ebp
    .cfi_def_cfa_offset 8
    .cfi_offset 5, -8
    movl    %esp, %ebp
    .cfi_def_cfa_register 5
    pushl   %esi
    pushl   %ebx
    andl    $-16, %esp
    subl    $16, %esp
    .cfi_offset 3, -16
    .cfi_offset 6, -12
    call    ___main
    movl    $32, (%esp)
    call    _malloc
    movl    $32, (%esp)
    movl    %eax, %esi
    call    _malloc
    movl    $-1431655766, (%esi)
    movl    $-1431655766, 4(%esi)
    xorl    %edx, %edx
    movl    $-1431655766, 8(%esi)
    movl    $-1431655766, 12(%esi)
    movl    $-1431655766, 16(%esi)
    movl    $-1431655766, 20(%esi)
    movl    $-1431655766, 24(%esi)
    movl    $-1431655766, 28(%esi)
    movl    $-1145324613, (%eax)
    movl    $-1145324613, 4(%eax)
    movl    $-1145324613, 8(%eax)
    movl    $-1145324613, 12(%eax)
    movl    $-1145324613, 16(%eax)
    movl    $-1145324613, 20(%eax)
    movl    $-1145324613, 24(%eax)
    movl    $-1145324613, 28(%eax)
    .p2align 4,,10
L7:
    movzbl  (%eax,%edx), %ecx
    xorb    %cl, (%esi,%edx)
    addl    $1, %edx
    cmpl    $32, %edx
    jne L7
    movl    $LC0, (%esp)
    xorl    %ebx, %ebx
    call    _printf
    .p2align 4,,10
L8:
    movzbl  (%esi,%ebx), %eax
    movl    $LC1, (%esp)
    movl    %eax, 4(%esp)
    addl    $1, %ebx
    call    _printf
    cmpl    $32, %ebx
    jne L8
    movl    $10, (%esp)
    call    _putchar
    leal    -8(%ebp), %esp
    xorl    %eax, %eax
    popl    %ebx
    .cfi_restore 3
    popl    %esi
    .cfi_restore 6
    popl    %ebp
    .cfi_def_cfa 4, 4
    .cfi_restore 5
    ret
    .cfi_endproc
LFE19:
    .def    _putchar;   .scl    2;  .type   32; .endef
    .def    _malloc;    .scl    2;  .type   32; .endef
    .def    _printf;    .scl    2;  .type   32; .endef