[Bug target/101816] New: slight missed optimization with __builtin_add_overflow with ^1

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101816

            Bug ID: 101816
           Summary: slight missed optimization with __builtin_add_overflow
                    with ^1
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: enhancement
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pinskia at gcc dot gnu.org
  Target Milestone: ---
            Target: x86_64-linux-gnu

Take:
void f(unsigned long long *x, unsigned long long y, unsigned long long z)
{
  int d = __builtin_add_overflow (*x,y,x);
  x[1] += z + !d;
}
Right now we produce:
        xorl    %eax, %eax
        addq    (%rdi), %rsi
        setc    %al
        movq    %rsi, (%rdi)
        xorq    $1, %rax
        addq    %rdx, %rax
        addq    %rax, 8(%rdi)
        ret

But the setc and xor could be combined into:
setnc   %al