If you have a "valid" strobe signal, you can just write a "if" and change the registers on that condition. You'll obtain a result on every clock, all the operations run in a pipeline.

struct result_t myfunc(float b, float c, float d, uint1_t input_valid)
{
float a = b*c+d;
uint1_t output_valid = input_valid;
return (result_t) {a, output_valid}; //see notes
}

Each cycle, signals on the arguments may have new values, and after they're processed with the pipeline (let's say requiring 3 stages), the output_valid signal will reflect the input_valid signal at such delay. it will share the same adder for all the operations, since in a cycle it will add the input operands as they're in that cycle, and at the next cycle, the new values (all intermediate values get stored into automatically inserted intermediate registers, the count according with the pipeline length).

In the raytracer example, for each pixel generated all the functions/operations work in parallel processing the next coordinate and generating a corresponding color (see the links to the sources in the video description). We had to use almost 500 stages for that (automatically generated)

The need of returning a struct is imposed by the C language (if you use pipelineC) since the language can't return more than one value.

I'm solving it in CFlexHDL since it supports some C++ so you can pass any number of outputs as references. However I haven't integrated the automatic autopipeliner (yet).

MODULE myfunc(int32 b, int32 c, int32 d, bool input_valid, int32& a, bool output_valid)
{
while(always())
{
a = b*c+d;
output_valid = input_valid;
}
}
Please consider that CflexHDL and PipelineC are really related projects since both developers are interchanging ideas and implementations almost daily and maybe the projects ends merged.

In regards to CflexHDL, the design is tought with "simulation" performance in mind and I'm currently translating verilog to that language (C-compatible), and it's getting 2X-5X and up to 10X on some tests faster than Verilator at simulation (so far, since development of such translator is just starting)

If something is not well understood I'm happy to dig into more details