[MLIR][mlir-link] Add hook to perform per Module computation before summary

This allows the linker interface to pre-compute some information that might be necessary for the linking.

Author: Jezurko

mlir/include/mlir/Linker/LinkerInterface.h

@@ -143,6 +143,12 @@ class SymbolLinkerInterface : public LinkerInterface<SymbolLinkerInterface> {
     return state.clone(src);
   }
 
+  /// Perform tasks that need to be computed on whole-module basis before actual summary.
+  /// E.g. Pre-compute COMDAT resolution before actually linking the modules.
+  virtual LogicalResult moduleOpSummary(ModuleOp module) {
+    return success();
+  }
+
   /// Dependencies of the given operation required to be linked.
   virtual SmallVector<Operation *>
   dependencies(Operation *op, SymbolTableCollection &collection) const = 0;
@@ -276,6 +282,14 @@ class SymbolLinkerInterfaces {
     return Conflict::noConflict(src);
   }
 
+  LogicalResult moduleOpSummary(ModuleOp src) {
+    for (SymbolLinkerInterface *linker : interfaces) {
+      if (failed(linker->moduleOpSummary(src)))
+        return failure();
+    }
+    return success();
+  }
+
 private:
   SetVector<SymbolLinkerInterface *> interfaces;
 };

mlir/lib/IR/BuiltinLinkerInterface.cpp

@@ -36,8 +36,11 @@ class BuiltinLinkerInterface : public ModuleLinkerInterface {
 
   LogicalResult summarize(ModuleOp src, unsigned flags) override {
     WalkResult result = src.walk([&](Operation *op) {
-      if (op == src)
+      if (op == src) {
+        if (symbolLinkers.moduleOpSummary(src).failed())
+            return WalkResult::interrupt();
         return WalkResult::advance();
+      }
 
       if (summarize(op, flags, /*forDependency=*/false).failed())
         return WalkResult::interrupt();