ARM VERSION 1.2 - Manual (Page 245)

Vector Floating-point Programming
ARM DUI 0068B Copyright © 2000, 2001 ARM Limited. All rights reserved. 6-7
6.3 Vector and scalar operations
You can use VFP arithmetic instructions to operate:
• on scalars
• on vectors
• on scalars and vectors together.
Use the LEN bits in the FPSCR to control the length of vectors (see FPSCR, the
floating-point status and control register on page 6-10).
When LEN is 1 all operations are scalar.
6.3.1 Control of scalar, vector and mixed operations
When LEN is greater than 1, the behavior of arithmetic operations depends on which
register bank the destination and operand registers are in (see Register banks on
page 6-5).
The behavior of instructions of the following general forms:
Op Fd,Fn,Fm
Op Fd,Fm
is as follows:
• If Fd is in the first bank of registers, s0 to s7 or d0 to d3, the operation is scalar.
• If the Fm is in the first bank of registers, but Fd is not, the operation is mixed.
• If neither Fd nor Fm are in the first bank of registers, the operation is vector.
Scalar operations
Op acts on the value in Fm , and the value in Fn if present. The result is placed in Fd .
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 .
Mixed scalar and vector operations
For single-operand instructions, Op acts on the single value in Fm . LEN copies of the result
are placed in the vector starting at Fd .
For multiple-operand instructions, 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 .