3 ms·

Having a mode that makes all existing arithmetic instructions interrupt sounds plausible, though there must be something I overlooked.

• tom_mellior 6y ago
  That wouldn't work well for C since signed overflow is undefined, but unsigned overflow is well-defined, with wrapping semantics. Making all existing arithmetic instructions trapping would mean paying trapping costs for well-defined unsigned overflow.
  • zeotroph 6y ago
    I think this would be a per-thread state which you toggle, defaulting to "off". Then instead of checking and branching after each operation you flip it on/off depending on the type of arithmetic you want. The trick would be to get to the minimal number of toggles and not do the "safe" thing and set it to on/off for each operation.
    • gpderetta 6y ago
      Generally this sort of global states are considered a misfeature. They are hard to use and impede cpu design (they are particularly bad for OoO). It is better to have per instruction flags. For exemple while SSE still has an fpu control word, explicit instructions were added for some stuff that historically was handled by the control register (rounding for example).