I have a simple question. When performing address computations, the size of the BASE and the INDEX are required to be the same. I presumed this was the case in the GATHER instructions.. but I don't believe it is so now. Can someone confirm? Namely.. I'm asking if you can use a 64-bit gpr BASE register, and use 32-bit indexes in an instruction like VGATHERDPS or VPGATHERDD. In these 2 instructions the indexes are 32-bit values, which I presume are sign extended to 64-bits when you have a 64-bit gpr BASE specified. I didn't find it clearly stated this was possible nor did I find it was prohibited.. so just wanted to clarify.
Thank you for any helpful and concise feedback