Control of scalar, vector, and mixed operations

You can use VFP arithmetic instructions to operate on:

Use the LEN bits in the FPSCR to control the length of vectors. When LEN is 1 all VFP operations are scalar.

When LEN is greater than 1, the VFP operation can be scalar, vector or mixed. The behavior of VFP arithmetic operations depends on which register bank the destination and operand registers are in.

The first bank of registers, s0 to s7 or d0 to d3 and the fifth bank of registers d16 to d19 are scalar banks. All other banks are vector banks. A vector operation or mixed operation is one where the destination register is in one of the vector banks.

Given instructions of the following general forms:

    Op  Fd,Fn,Fm
    Op  Fd,Fm

where:

Op

is the VFP instruction

Fd

is the destination register

Fn

is an operand register

Fm

is the only or second operand register

the behavior of the operation is as follows:

In scalar operations, Op acts on the value in Fm, and the value in Fn if present. The result is placed in Fd.

In vector operations, Op acts on the values in the vector starting at Fm, together with the values in the vector starting at Fn if present. The results are placed in the vector starting at Fd.

In mixed operations, with a single operand, Op acts on the single value in Fm and LEN copies of the result are placed in the vector starting at Fd.

In mixed operations, with two operands, Op acts on the single value in Fm, together with the values in the vector starting at Fn. The results are placed in the vector starting at Fd.

Show/hideSee also

Copyright © 2010-2011 ARM. All rights reserved.ARM DUI 0473C
Non-ConfidentialID080411