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5.8.4. VEXT

VEXT (Vector Extract) extracts 8-bit elements from the bottom end of the second operand vector and the top end of the first, concatenates them, and places the result in the destination vector. See Figure 5.2 for an example.

Figure 5.2. Operation of doubleword VEXT for imm = 3

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Syntax

VEXT{cond}.8 {Qd}, Qn, Qm, #imm

VEXT{cond}.8 {Dd}, Dn, Dm, #imm

where:

cond

is an optional condition code (see Condition codes).

Qd, Qn, Qm

specifies the destination register, the first operand register, and the second operand register, for a quadword operation.

Dd, Dn, Dm

specifies the destination register, the first operand register, and the second operand register, for a doubleword operation.

imm

is the number of 8-bit elements to extract from the bottom of the second operand vector, in the range 0-7 for doubleword operations, or 0-15 for quadword operations.

VEXT pseudo-instruction

You can specify a datatype of 16, 32, or 64 instead of 8. In this case, #imm refers to halfwords, words, or doublewords instead of referring to bytes, and the allowed ranges are correspondingly reduced.

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