Falcor Compilation to SPIR-V with no Inlining

[sriramm-nv]

Problem Statement
Falcor provides a wide set of shaders that can be compiled via Slang, to generate SPIR-V. The direct-spirv lowering path, bypasses glslang, and stands as a first-class compilation pipeline for outputting SPIR-V code.
However, currently, there is a need for performing spirv-opt on this SPIR-V output code, in order to generate a more-compact output, for further lowering via GLV compilation pipeline. The main purpose of spirv-opt is to perform Inlining of the functions, and this currently adds compilation time overhead for each shader that goes through the pipeline.

Work to be done

1. Disable spirv-opt for the Falcor shader compilation via Direct SPIR-V emit.
   a. Use Vulkan backend
   b. Use Direct SPIR-V backend instead of Glslang
   c. Disable SPIR-V optimization (Use -O0)
2. Identify bugs during compilation
   a. Report bugs to GLV team with appropriate container files for repro.
   b. Pick up bugs and fix as needed.