Vector Floating-point Programming
ARM DUI 0068B Copyright © 2000, 2001 ARM Limited. All r ights 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
page6-5).
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 th e
values in the vector sta rting at
Fn
. The results are pla ced in the vector st arting at
Fd
.