Reflection: allow querying of semantics on varying input/output (#224)

This is functionality required to support a Falcor bug fix.

Most of the code to compute the right semantic name/index for a parameter was already present.
This change adds:

- Storage for semantic name/index on every `VarLayout`
  - Note: this is wasteful and should be optimized later

- A public API to query the semantic name/index
  - The contract is that this API returns `NULL` if the parameter had no semantic

- A bit of work in `parameter-binding.cpp` to attach semantics to varying input/output when traversing varying parameters.
  - Note: this is intentionally set up so that it associates semantics even with non-leaf parameters, so that an API user can query the semantic of a `struct` parameter and know that its members will be assigned sequential semantic indices from its starting value.

- Support for dumping this information in reflection tests

One notable thing that I did *not* change here is that the reflection test fixture doesn't report information on the output of an entry point, even though it really should. That should be fixed in a separate change, though, because it would affect many of the expected outputs.

1 files changed, 21 insertions, 0 deletions

diff --git a/source/slang/parameter-binding.cpp b/source/slang/parameter-binding.cpp
index 4fbec5652..fed838e6b 100644
--- a/source/slang/parameter-binding.cpp
+++ b/source/slang/parameter-binding.cpp
@@ -1190,6 +1190,27 @@ static RefPtr<TypeLayout> processEntryPointParameter(
     EntryPointParameterState const& state,
     RefPtr<VarLayout>               varLayout)
 {
+    // If there is an available semantic name and index,
+    // then we should apply it to this parameter unconditionally
+    // (that is, not just if it is a leaf parameter).
+    auto optSemanticName    =  state.optSemanticName;
+    if (optSemanticName && varLayout)
+    {
+        // Always store semantics in upper-case for
+        // reflection information, since they are
+        // supposed to be case-insensitive and
+        // upper-case is the dominant convention.
+        String semanticName = *optSemanticName;
+        String sn = semanticName.ToUpper();
+
+        auto semanticIndex      = *state.ioSemanticIndex;
+
+        varLayout->semanticName = sn;
+        varLayout->semanticIndex = semanticIndex;
+        varLayout->flags |= VarLayoutFlag::HasSemantic;
+    }
+
+
     // Scalar and vector types are treated as outputs directly
     if(auto basicType = type->As<BasicExpressionType>())
     {