Ну давайте вместе почитаем .
Читать все , жирное читать до осознания !!!!
Спойлер
This user manual describes the CMSIS DSP software library, a suite of common signal processing functions for use on Cortex-M processor based devices.
The library is divided into a number of modules each covering a specific category:
Basic math functions
Fast math functions
Complex math functions
Filters
Matrix functions
Transforms
Motor control functions
Statistical functions
Support functions
Interpolation functions
The library has separate functions for operating on 8-bit integers, 16-bit integers, 32-bit integer and 32-bit floating-point values.
Processor Support
The library is completely written in C and is fully CMSIS compliant. High performance is achieved through maximum use of Cortex-M4 intrinsics.
The supplied library source code also builds and runs on the Cortex-M3 and Cortex-M0 processor, with the DSP intrinsics being emulated through software.
Toolchain Support
The library has been developed and tested with MDK-ARM version 4.21. The library is being tested in GCC and IAR toolchains and updates on this activity will be made available shortly.
Using the Library
The library installer contains prebuilt versions of the libraries in the Lib folder.
arm_cortexM4lf_math.lib (Little endian and Floating Point Unit on Cortex-M4)
arm_cortexM4bf_math.lib (Big endian and Floating Point Unit on Cortex-M4)
arm_cortexM4l_math.lib (Little endian on Cortex-M4)
arm_cortexM4b_math.lib (Big endian on Cortex-M4)
arm_cortexM3l_math.lib (Little endian on Cortex-M3)
arm_cortexM3b_math.lib (Big endian on Cortex-M3)
arm_cortexM0l_math.lib (Little endian on Cortex-M0)
arm_cortexM0b_math.lib (Big endian on Cortex-M3)
The library functions are declared in the public file arm_math.h which is placed in the Include folder. Simply include this file and link the appropriate library in the application and begin calling the library functions. The Library supports single public header file arm_math.h for Cortex-M4/M3/M0 with little endian and big endian. Same header file will be used for floating point unit(FPU) variants. Define the appropriate pre processor MACRO ARM_MATH_CM4 or ARM_MATH_CM3 or ARM_MATH_CM0 depending on the target processor in the application.
Examples
The library ships with a number of examples which demonstrate how to use the library functions.
Building the Library
The library installer contains project files to re build libraries on MDK Tool chain in the CMSIS\DSP_Lib\Source\ARM folder.
arm_cortexM0b_math.uvproj
arm_cortexM0l_math.uvproj
arm_cortexM3b_math.uvproj
arm_cortexM3l_math.uvproj
arm_cortexM4b_math.uvproj
arm_cortexM4l_math.uvproj
arm_cortexM4bf_math.uvproj
arm_cortexM4lf_math.uvproj
Each library project have differant pre-processor macros.
ARM_MATH_CMx: Define macro ARM_MATH_CM4 for building the library on Cortex-M4 target, ARM_MATH_CM3 for building library on Cortex-M3 target and ARM_MATH_CM0 for building library on cortex-M0 target.
ARM_MATH_BIG_ENDIAN: Define macro ARM_MATH_BIG_ENDIAN to build the library for big endian targets. By default library builds for little endian targets.
ARM_MATH_MATRIX_CHECK: Define macro for checking on the input and output sizes of matrices
ARM_MATH_ROUNDING: Define macro for rounding on support functions
__FPU_PRESENT: Initialize macro __FPU_PRESENT = 1 when building on FPU supported Targets. Enable this macro for M4bf and M4lf libraries
The project can be built by opening the appropriate project in MDK-ARM 4.21 chain and defining the optional pre processor MACROs detailed above.
Copyright Notice
Copyright (C) 2010 ARM Limited. All rights reserved.
Из прочтенного следует, что для полноценного юзанья FPU нужно включить дефайн
__FPU_PRESENT, сей дефайн уже прописан в stm32f4xx.h.
Далее надо подключить мат либы , для этого надо подключить хэдер
arm_math.h и прописать дефайн
ARM_MATH_CM4 в препроцессоре .
Осталось включить дефайн
__FPU_USED(что в купе с __FPU_PRESENT включает сопроцессор)- та самая галочка , которую вы судорожно переключаете.

Это все в
Keil и
Iar , в ГНУтых компилях надо еще саму либу подключить ручками .