Advanced SIMD scalars
Some Advanced SIMD instructions act on scalars in combination with vectors. Advanced SIMD scalars can be 8-bit, 16-bit, 32-bit, or 64-bit.
In A32/T32 Advanced SIMD instructions, the instruction syntax refers to a
single element in a vector register using an index,
into the vector, so that
xth element in vector
. In A64 Advanced SIMD instructions, you append the
index to the element size specifier, so that
xth doubleword element in vector
In A64 Advanced SIMD scalar instructions, you refer to registers
using a name that indicates the number of significant bits. The
is the register number (0-31).
The unused high bits are ignored on a read and set to zero on a
Other than A32/T32 Advanced SIMD multiply instructions, instructions that access scalars can access any element in the register bank.
A32/T32 Advanced SIMD multiply instructions only allow 16-bit or 32-bit scalars, and can only access the first 32 scalars in the register bank. That is, in multiply instructions:
- 16-bit scalars
are restricted to registers D0-D7, with
in the range 0-3.
- 32-bit scalars are restricted to registers D0-D15,
either 0 or 1.