[llvm] [HLSL] Analyze update counter usage (PR #130356)

[Justin Bogner via llvm-commits]

================
@@ -407,6 +411,77 @@ class DXILResourceTypeMap {
   }
 };
 
+enum ResourceCounterDirection {
+  Increment,
+  Decrement,
+  Unknown,
+};
+
+class DXILResourceCounterDirectionMap {
+  std::vector<std::pair<dxil::ResourceBindingInfo, ResourceCounterDirection>>
+      CounterDirections;
+
+public:
+  bool invalidate(Module &M, const PreservedAnalyses &PA,
+                  ModuleAnalysisManager::Invalidator &Inv);
+
+  void populate(Module &M, ModuleAnalysisManager &AM);
+
+  ResourceCounterDirection
+  operator[](const dxil::ResourceBindingInfo &Info) const {
+    auto Lower = std::lower_bound(
+        CounterDirections.begin(), CounterDirections.end(),
+        std::pair{Info, ResourceCounterDirection::Unknown},
+        [](auto lhs, auto rhs) { return lhs.first < rhs.first; });
+
+    if (Lower == CounterDirections.end()) {
+      return ResourceCounterDirection::Unknown;
+    }
+
+    if (Lower->first != Info) {
+      return ResourceCounterDirection::Unknown;
+    }
+
+    return Lower->second;
+  }
+};
+
+class DXILResourceCounterDirectionAnalysis
+    : public AnalysisInfoMixin<DXILResourceCounterDirectionAnalysis> {
+  friend AnalysisInfoMixin<DXILResourceCounterDirectionAnalysis>;
+
+  static AnalysisKey Key;
+
+public:
+  using Result = DXILResourceCounterDirectionMap;
+
+  DXILResourceCounterDirectionMap run(Module &M, ModuleAnalysisManager &AM) {
+    DXILResourceCounterDirectionMap DRCDM{};
+    DRCDM.populate(M, AM);
+    return DRCDM;
+  }
+};
+
+class DXILResourceCounterDirectionWrapperPass : public ImmutablePass {
+  DXILResourceCounterDirectionMap DRCDM;
+
+  virtual void anchor();
----------------
bogner wrote:

These anchor methods exist in order to "anchor" to a particular object file, which generally helps with object file size and link times from not needing to emit vtables (and potentially RTTI) into every object where the type is references and then ODR those definitions. They're necessary when there aren't any virtual methods defined in the cpp file (like when the only virtual method is the empty destructor, say). Since we've switched this to a ModulePass and some of the overridden methods are implemented out of line it's no longer strictly necessary here.

https://github.com/llvm/llvm-project/pull/130356