[clang] [HLSL] Collect explicit resource binding information (PR #111203)

[Damyan Pepper via cfe-commits]

================
@@ -58,31 +56,82 @@ static RegisterType getRegisterType(ResourceClass RC) {
   llvm_unreachable("unexpected ResourceClass value");
 }
 
-static RegisterType getRegisterType(StringRef Slot) {
+// Converts the first letter of string Slot to RegisterType.
+// Returns false if the letter does not correspond to a valid register type.
+static bool convertToRegisterType(StringRef Slot, RegisterType *RT) {
+  assert(RT != nullptr);
   switch (Slot[0]) {
   case 't':
   case 'T':
-    return RegisterType::SRV;
+    *RT = RegisterType::SRV;
+    return true;
   case 'u':
   case 'U':
-    return RegisterType::UAV;
+    *RT = RegisterType::UAV;
+    return true;
   case 'b':
   case 'B':
-    return RegisterType::CBuffer;
+    *RT = RegisterType::CBuffer;
+    return true;
   case 's':
   case 'S':
-    return RegisterType::Sampler;
+    *RT = RegisterType::Sampler;
+    return true;
   case 'c':
   case 'C':
-    return RegisterType::C;
+    *RT = RegisterType::C;
+    return true;
   case 'i':
   case 'I':
-    return RegisterType::I;
+    *RT = RegisterType::I;
+    return true;
   default:
-    return RegisterType::Invalid;
+    return false;
   }
 }
 
+static ResourceClass getResourceClass(RegisterType RT) {
+  switch (RT) {
+  case RegisterType::SRV:
+    return ResourceClass::SRV;
+  case RegisterType::UAV:
+    return ResourceClass::UAV;
+  case RegisterType::CBuffer:
+    return ResourceClass::CBuffer;
+  case RegisterType::Sampler:
+    return ResourceClass::Sampler;
+  case RegisterType::C:
+  case RegisterType::I:
+    llvm_unreachable("unexpected RegisterType value");
+  }
+}
+
+DeclBindingInfo *ResourceBindings::addDeclBindingInfo(const VarDecl *VD,
+                                                      ResourceClass ResClass) {
+  assert(getDeclBindingInfo(VD, ResClass) == nullptr &&
+         "DeclBindingInfo already added");
+  DeclToBindingListIndex.try_emplace(VD, BindingsList.size());
----------------
damyanp wrote:

Some explanation for why try_emplace is used here might be good (I know it's documented in the class, but this might be where someone reading it might more wonder why it is done like this:

```suggestion
    // VD's may have entries for mutliple ResClass's. DeclToBindingListIndex stores the index of the 
    // first binding we saw for this decl, if there are any additional ones then that index shouldn't be updated. 
    DeclToBindingListIndex.try_emplace(VD, BindingsList.size());
```


https://github.com/llvm/llvm-project/pull/111203