Potential memory leak in program compilation

[Hyiker]

Problem

Observed both in 7.0 and 8.0. A minimal reproduce:

1. Open an arbitrary scene with emissive meshes in Mogwai and load PathTracer script.
2. Adjust the emissive material parameters
3. As you adjust the parameters, memory grow linearly.

Possible cause

I tried to dig out the root cause, but only managed to find out the problem has something to do with slang program compilation: Visual Studio shows that every time spCompile is called, we can see a memory growth(+200M every time, on Windows, Falcor 7.0).

[jkwak-work]

I think this is addressed recently,

• Fix one of memory leaks from module shader-slang/slang#7290