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PEXTRB

Extracts a byte from a source operand at a specified index and stores it into the destination operand.

The following table covers what the source and destinations can be:

DO NOT support LOCK

This instruction is available only in 64-bit mode. It requires the BMI1 instruction set extension to be supported by the processor.

The index of the byte to be extracted is specified by an immediate value. This immediate MUST be an unsigned integer. If the index is out of range for the size of the source operand, the behavior is undefined. The destination register is zero-extended to the size of the register (r8).