3 ms·

The intro matter is a bit hard to parse, but my understanding is that everything on that page is supposed to be constant-time, but the things that have "True" i

The intro matter is a bit hard to parse, but my understanding is that everything on that page is supposed to be constant-time, but the things that have "True" in the final column are the ones that aren't constant-time unless you twiddle on MSR on some systems. Most of the integer instructions you'd expect to be constant-time are in fact constant-time; it's a slice of vector integer multiply (and integer multiply-adds) that are inadvertently not constant-time.

AshamedCaptain 4y ago
No, that's the wrong way to parse it, as there are explicitly _two_ bits on the MSR (DOITM and MCDT), and this thread is about DOITM. All the instructions in the list are no longer (guaranteed to be?) constant-time unless the DOITM bit is set. > Specifically, when data operand independent timing mode [DOITM] is enabled, instructions within the data operand independent timing subset execute with timing (in terms of processor cycles) that is independent of the data values in the sources of the instruction