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CONFIG_FPU_SHARING¶
FPU register sharing
Type: bool
Help¶
This option enables preservation of the hardware floating point registers across context switches to allow multiple threads to perform concurrent floating point operations.
Note that on Cortex-M processors with the floating point extension we enable by default the FPU register sharing mode, as some GCC compilers may activate a floating point context by generating FP instructions for any thread, and that context must be preserved when switching such threads in and out. The developers can still disable the FP sharing mode in their application projects, and switch to Unshared FP registers mode, if it is guaranteed that the image code does not generate FP instructions outside the single thread context that is allowed to do so.
Default¶
y if
ARM&&ARMV7_M_ARMV8_M_FP
Kconfig definition¶
At arch/Kconfig:765
Included via Kconfig:8 → Kconfig.zephyr:29
Menu path: (Top) → Floating Point Options → Enable floating point unit (FPU)
config FPU_SHARING
bool "FPU register sharing"
default y if ARM && ARMV7_M_ARMV8_M_FP
depends on FPU && MULTITHREADING
help
This option enables preservation of the hardware floating point registers
across context switches to allow multiple threads to perform concurrent
floating point operations.
Note that on Cortex-M processors with the floating point extension we
enable by default the FPU register sharing mode, as some GCC compilers
may activate a floating point context by generating FP instructions for
any thread, and that context must be preserved when switching such
threads in and out. The developers can still disable the FP sharing
mode in their application projects, and switch to Unshared FP registers
mode, if it is guaranteed that the image code does not generate FP
instructions outside the single thread context that is allowed to do so.
(The ‘depends on’ condition includes propagated dependencies from ifs and menus.)