Question

The instruction that shifts 8 LSB bits of ECX into the MSB positions of EAX, one by one starting from LSB of ECX is

(a) SHLD ECX,EAX,8

(b) SHLD EAX,ECX,8

(c) SHRD ECX,EAX,8

(d) SHRD EAX,ECX,8

I have been asked this question in an online quiz.

This key question is from Enhanced Instruction Set of 80386 in chapter 32-bit Processors-80386, 80387 and 80486 of Microprocessor

Answer 1

The correct option is (d) SHRD EAX,ECX,8

Best explanation: The SHRD instruction shifts the specified number of bits in the instruction, from the lower side (i.e. LSB) of the source operand into the upper side (i.e. MSB) of the destination operand.