The 'hf' not only refers to the presence of a hardware floating point unit, but also that the floating point function arguments are passed in floating point reg

The 'hf' not only refers to the presence of a hardware floating point unit, but also that the floating point function arguments are passed in floating point registers in the ABI. For interwork with precompiled binaries, the full ABI support assuming hardware floating point trailed behind the simple presence of an FPU for a surprisingly long amount of time. For a real long time, the asm would be crazy, passing floating point arguments into the integer registers at every function call boundary, just to pass them back into the FPU registers to perform any work on them.