About gcc-compiled x86_64 code and C code optimization

I compiled the following C code:

typedef struct {
    long x, y, z;
} Foo;

long Bar(Foo *f, long i)
{
    return f[i].x + f[i].y + f[i].z;
}

with the team gcc -S -O3 test.c. Here is the output Bar function:

    .section    __TEXT,__text,regular,pure_instructions
    .globl  _Bar
    .align  4, 0x90
_Bar:
Leh_func_begin1:
    pushq   %rbp
Ltmp0:
    movq    %rsp, %rbp
Ltmp1:
    leaq    (%rsi,%rsi,2), %rcx
    movq    8(%rdi,%rcx,8), %rax
    addq    (%rdi,%rcx,8), %rax
    addq    16(%rdi,%rcx,8), %rax
    popq    %rbp
    ret
Leh_func_end1:

I have a few questions about this assembler:

• What is the purpose of " pushq %rbp", " movq %rsp, %rbp" and " popq %rbp" if no functions are used in the body rbp, nor rsp?
• Why do rsithey rdiautomatically contain arguments to the C function ( iand, faccordingly), without reading them from the stack?

• Foo 88 (11 long s), leaq imulq. , "" , ( )? leaq :

  imulq   $88, %rsi, %rcx