3 ms·
SHL masks the shift count, PSLLW/D/Q overshifts "correctly." While that part of the specification predates MMX, they may very well have had the possibility in
by mike_hock 3y ago
SHL masks the shift count, PSLLW/D/Q overshifts "correctly."
While that part of the specification predates MMX, they may very well have had the possibility in mind that shifts might be accomplished by multiple instructions with different behavior (if we're gonna give them this much credit). But one way or the other, it's useful now for auto-vectorization.