Far classes

[John Rose]

On Jul 13, 2024, at 12:58 AM, Thomas Stüfe <thomas.stuefe at gmail.com> wrote:


The second might also enable a compact flow-free decoding:

Klass* get_klass_3(uint16_t klassCode) {
  bool_t is_near = klassCode < (1<<8);  // 8 upper bits zero?
  Klass** near_base = (Klass**) this;
  constexpr Klass** far_base = NEAR_CLASSES[- (1<<8)];
  Klass** base = is_near ? near_base : far_base;  //CMOV
  return base[klassCode];
}

Beautiful :)

Question though, should it not be reverse?

Looks like I made several bugs in there. Maybe this is more correct:

Klass* get_klass_3(uint16_t klassCode) {
  bool_t is_near = klassCode >= (1<<8);  // 8 upper bits nonzero?
  constexpr Klass** near_base = NEAR_CLASSES[- (1<<8)];
  Klass** far_base = (Klass**) this;
  Klass** base = is_near ? near_base : far_base;  //CMOV
  return base[klassCode];
}

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