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DevHeads IoT Integration ServerDIIS
DevHeads IoT Integration Server•14mo ago
Marvee Amasi

How can I change VEX instructions between 16, 32, and 64-bit modes?

Does anyone understand how to work with
MASKMOVDQU
MASKMOVDQU
, cus I'm stuck by it's instruction from the page 902 of the Intel x64 manual . I am confused on how to adjust the register sizes for this instruction. Here the documentation mentions that the default memory location is
DS:DI/EDI/RDI
DS:DI/EDI/RDI
, but the opcode includes
0x66
0x66


How should I handle this
0x66
0x66
? Should I replace it with
0x67
0x67
or use the
REX.W
REX.W
prefix for
EDI/RDI
EDI/RDI
registers to adjust for the different sizes?

So there is a VEX version of this instruction listed as:
VEX.128.66.0F.WIG F7 /r
VEX.128.66.0F.WIG F7 /r

How can I change VEX instructions between 16, 32, and 64-bit modes?
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