Question

I have read many question about improving the performance of C++ and C code . Almost all the answer people have end up with observing assembly code generated by the compiler.

If I want to understand this technique, what are the best resource for that?

Answer 1

Practice is your best teacher

Write a simple test file:

#include <stdio.h>

int main() {
    printf("Hello %s !\n", "world");
}

then gcc -S test.cpp will give you the generated assembly code in test.s. Add -Ox if you want.

    .file   "test.cpp"
    .section    .rodata
.LC0:
    .string "world"
.LC1:
    .string "Hello %s !\n"
    .text
    .globl  main
    .type   main, @function
main:
.LFB0:
    .cfi_startproc
    pushq   %rbp
    .cfi_def_cfa_offset 16
    .cfi_offset 6, -16
    movq    %rsp, %rbp
    .cfi_def_cfa_register 6
    movl    $.LC0, %esi
    movl    $.LC1, %edi
    movl    $0, %eax
    call    printf
    movl    $0, %eax
    popq    %rbp
    .cfi_def_cfa 7, 8
    ret
    .cfi_endproc
.LFE0:
    .size   main, .-main
    .ident  "GCC: (Debian 4.7.0-13) 4.7.0"
    .section    .note.GNU-stack,"",@progbits

If you have difficulties understanding the assembly language, you’d better start from GNU assembly language and linkers & loaders, and also Intel® 64 and IA-32 Architectures Software Developer’s Manual. It is a great reference book.