Outlined thread locals.

static thread_local uint64_t RandomStateA =
    static_cast<uint64_t>(time(nullptr));
static thread_local uint64_t RandomStateB = xorShiftStar64();

uint64_t getRandomUnsigned64() {
  uint64_t A = RandomStateA;
  const uint64_t B = RandomStateB;
  RandomStateA = B;

  A ^= A << 23;
  A ^= A >> 17;
  A ^= B ^ (B >> 26);

  RandomStateB = A;
  return A + B;
}

==========================================================================
0000000000400780 <gwp_asan::random::getRandomUnsigned64()>:
  400780:       41 57                   push   %r15
  400782:       41 56                   push   %r14
  400784:       41 55                   push   %r13
  400786:       41 54                   push   %r12
  400788:       53                      push   %rbx
  400789:       66 66 66 64 48 8b 04    data16 data16 data16 mov %fs:0x0,%rax
  400790:       25 00 00 00 00
  400795:       49 89 c6                mov    %rax,%r14
  400798:       8a 88 f8 ff ff ff       mov    -0x8(%rax),%cl
  40079e:       84 c9                   test   %cl,%cl
  4007a0:       74 55                   je     4007f7 <gwp_asan::random::getRandomUnsigned64()+0x77>
  4007a2:       4d 8b a6 e8 ff ff ff    mov    -0x18(%r14),%r12
  4007a9:       4d 8b ae f0 ff ff ff    mov    -0x10(%r14),%r13
  4007b0:       4c 89 f0                mov    %r14,%rax
  4007b3:       4d 89 ae e8 ff ff ff    mov    %r13,-0x18(%r14)
  4007ba:       4c 89 e3                mov    %r12,%rbx
  4007bd:       48 c1 e3 17             shl    $0x17,%rbx
  4007c1:       4c 31 e3                xor    %r12,%rbx
  4007c4:       4c 89 e8                mov    %r13,%rax
  4007c7:       48 c1 e8 1a             shr    $0x1a,%rax
  4007cb:       4c 31 e8                xor    %r13,%rax
  4007ce:       48 31 d8                xor    %rbx,%rax
  4007d1:       48 c1 eb 11             shr    $0x11,%rbx
  4007d5:       48 31 c3                xor    %rax,%rbx
  4007d8:       84 c9                   test   %cl,%cl
  4007da:       0f 84 d6 00 00 00       je     4008b6 <gwp_asan::random::getRandomUnsigned64()+0x136>
  4007e0:       49 89 9e f0 ff ff ff    mov    %rbx,-0x10(%r14)
  4007e7:       49 01 dd                add    %rbx,%r13
  4007ea:       4c 89 e8                mov    %r13,%rax
  4007ed:       5b                      pop    %rbx
  4007ee:       41 5c                   pop    %r12
  4007f0:       41 5d                   pop    %r13
  4007f2:       41 5e                   pop    %r14
  4007f4:       41 5f                   pop    %r15
  4007f6:       c3                      retq