[llvm] [DirectX] Implement DXILResourceImplicitBinding pass (PR #138043)

[Ashley Coleman via llvm-commits]

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@@ -998,6 +998,61 @@ void DXILResourceBindingInfo::populate(Module &M, DXILResourceTypeMap &DRTM) {
   }
 }
 
+// returns false if binding could not be found in given space
+std::optional<uint32_t>
+DXILResourceBindingInfo::findAvailableBinding(dxil::ResourceClass RC,
+                                              uint32_t Space, int32_t Size) {
+  BindingSpaces &BS = getBindingSpaces(RC);
+  RegisterSpace &RS = BS.getOrInsertSpace(Space);
+  return RS.findAvailableBinding(Size);
+}
+
+DXILResourceBindingInfo::RegisterSpace &
+DXILResourceBindingInfo::BindingSpaces::getOrInsertSpace(uint32_t Space) {
+  for (auto *I = Spaces.begin(); I != Spaces.end(); ++I) {
+    if (I->Space == Space)
+      return *I;
+    if (I->Space < Space)
+      continue;
+    return *Spaces.insert(I, Space);
+  }
+  return Spaces.emplace_back(Space);
+}
+
+std::optional<uint32_t>
+DXILResourceBindingInfo::RegisterSpace::findAvailableBinding(int32_t Size) {
+  assert((Size == -1 || Size > 0) && "invalid size");
+
+  std::optional<uint32_t> RegSlot;
+  if (FreeRanges.empty())
+    return RegSlot;
----------------
V-FEXrt wrote:

This is an error case right? Please just return nullopt directly if so
```suggestion
    return std::nullopt;
```

https://github.com/llvm/llvm-project/pull/138043