How to preserve comments in glsl files?

We set -g, but I noted that glslc says " Generate source-level debug information. Currently this option has no effect.". I don't see any comments by the time we've run spirv-opt and spirv-cross back to Metal. The original GLSL has comments that are important to preserve in debug builds. It may be that we need flags subsequent to glslc, so I will look at the preprocessed output.