[Polybench FP] Stencil ADI

[rachitnigam]

Example PR for porting a polybench benchmark to use a fixed point implementation.
It uses the m4 preprocessor to define constants and types in the file.
This allows us to write one implementation that works for both bit types and
fix types.

Steps

• Syntactic rewrite of C++ program to Dahlia
• Dahlia compiler reports no errors
• Dahlia compiler generates valid Calyx program
• Calyx and Dahlia programs generate the same result
• Calyx and C++ programs generate same result with ubit inputs
• Calyx and C++ programs generate same result with fix inputs

[rachitnigam]

This benchmark tries to compute 1/20 in one of the first statements and therefore does not work with C++ simulation (immediately gets a divide by zero error).