On Apr 21, 2022, at 08:43:55, Seymour J Metz wrote: > > The question is not whether it is possible to detect overflow, but rather how > easy it is. Instructions for signed arithmetic set the condition code > appropriately for signed operands, but not for unsigned operands, e.g., > adding 00000001 to FFFFFFFF with A gives a zero condition code while AL > gives an overflow condition code. If there were no AL instruction then > detecting the overflow would be more awkward. > I believe it's the opposite. A and S report overflow; AL and SL do not; rather, AL and SL report a carry from the MSB.
On Apr 21, 2022, at 08:46:26, Seymour J Metz wrote: > > Well, in the case of S/370 the compiler could emit JO or JNO after the add. > That may be unnecessary. Simply enable trap on Overflow in the Program Mask. Depending on what recovery action the programmer intends to take. -- gil
