2 docs tagged with "fpu"

A context switch is not a function call. A function call returns to its caller; a context switch enters on one task's stack and leaves on another's, and the code that resumes has no idea it was ever stopped. There is no C construct for that. What makes it possible on a Cortex-M is that the processor already performs most of it, for free, every time an exception is taken — and that an exception return reads its destination out of memory rather than from a register, so pointing it at a different stack points it at a different task.

Writing float in C on a microcontroller does not tell you what the hardware will do. The same line of source can compile to one instruction, to a forty-cycle library call, or to a two-hundred-cycle double-precision emulation — and the compiler chooses silently, based on flags you may not have set deliberately. Nothing in the source distinguishes the three cases, which is why "why is my control loop suddenly missing deadlines" is so often a floating-point question.