Annoying silly warning emitted by gcc?

[Joe Buck]

On Wed, Jan 23, 2019 at 4:16 PM Warren D Smith <warren.wds@gmail.com> wrote:
>
> x = x^x;
>
> The purpose of the above is to load "x" with zero.

Don't waste your time.  Intel was offering that advice to writers of assembly language and compilers.  Gcc already does the right thing.

Try the following on an Intel/AMD machine:

% cat z.c
long long zero() {
    long long tmp = 0LL;
    return tmp;
}
% gcc -O2 -S z.c
% cat z.s
        .file   "z.c"
        .text
        .p2align 4,,15
        .globl  zero
        .type   zero, @function
zero:
.LFB0:
        .cfi_startproc
        xorl    %eax, %eax
        ret
        .cfi_endproc
.LFE0:
        .size   zero, .-zero
        .ident  "GCC: (GNU) 4.8.3"
        .section        .note.GNU-stack,"",@progbits