When an instruction operand is outside the range allowed for that
particular instruction field, as can transform the code
to use a functionally-equivalent instruction or sequence of
instructions. This process is known as relaxation. This is
typically done for branch instructions because the distance of the
branch targets is not known until assembly-time. The Xtensa assembler
offers branch relaxation and also extends this concept to function
calls, MOVI instructions and other instructions with immediate
fields.