Add support for nested symbol references.

This change allows for adding additional nested references to a SymbolRefAttr to allow for further resolving a symbol if that symbol also defines a SymbolTable. If a referenced symbol also defines a symbol table, a nested reference can be used to refer to a symbol within that table. Nested references are printed after the main reference in the following form:

  symbol-ref-attribute ::= symbol-ref-id (`::` symbol-ref-id)*

Example:

  module @reference {
    func @nested_reference()
  }

  my_reference_op @reference::@nested_reference

Given that SymbolRefAttr is now more general, the existing functionality centered around a single reference is moved to a derived class FlatSymbolRefAttr. Followup commits will add support to lookups, rauw, etc. for scoped references.

PiperOrigin-RevId: 279860501

1 files changed, 3 insertions, 1 deletions

diff --git a/mlir/lib/Analysis/CallGraph.cpp b/mlir/lib/Analysis/CallGraph.cpp
index 3c02802dd35..2b5894ff162 100644
--- a/mlir/lib/Analysis/CallGraph.cpp
+++ b/mlir/lib/Analysis/CallGraph.cpp
@@ -184,7 +184,9 @@ CallGraphNode *CallGraph::resolveCallable(CallInterfaceCallable callable,
   // Get the callee operation from the callable.
   Operation *callee;
   if (auto symbolRef = callable.dyn_cast<SymbolRefAttr>())
-    callee = SymbolTable::lookupNearestSymbolFrom(from, symbolRef.getValue());
+    // TODO(riverriddle) Support nested references.
+    callee = SymbolTable::lookupNearestSymbolFrom(from,
+                                                  symbolRef.getRootReference());
   else
     callee = callable.get<Value *>()->getDefiningOp();