arch: xtensa: save FPU register in context switching

Save FP user register and FP register file during context switch.

This change enables shared FP registers mode using CONFIG_FPU_SHARING.

Since there is no lazy stacking, the FPU registers will be saved regardless
of whether floating point calculations are performed in the threads when
CONFIG_FPU_SHARING is enabled. This require 72 additional bytes in the
stack memory.

Signed-off-by: Lucas Tamborrino <lucas.tamborrino@espressif.com>
4 files changed