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, 7 insertions, 2 deletions

diff --git a/mlir/lib/IR/Builders.cpp b/mlir/lib/IR/Builders.cpp
index 24ae2072f77..afdeefd023c 100644
--- a/mlir/lib/IR/Builders.cpp
+++ b/mlir/lib/IR/Builders.cpp
@@ -150,15 +150,20 @@ ArrayAttr Builder::getArrayAttr(ArrayRef<Attribute> value) {
   return ArrayAttr::get(value, context);
 }
 
-SymbolRefAttr Builder::getSymbolRefAttr(Operation *value) {
+FlatSymbolRefAttr Builder::getSymbolRefAttr(Operation *value) {
   auto symName =
       value->getAttrOfType<StringAttr>(SymbolTable::getSymbolAttrName());
   assert(symName && "value does not have a valid symbol name");
   return getSymbolRefAttr(symName.getValue());
 }
-SymbolRefAttr Builder::getSymbolRefAttr(StringRef value) {
+FlatSymbolRefAttr Builder::getSymbolRefAttr(StringRef value) {
   return SymbolRefAttr::get(value, getContext());
 }
+SymbolRefAttr
+Builder::getSymbolRefAttr(StringRef value,
+                          ArrayRef<FlatSymbolRefAttr> nestedReferences) {
+  return SymbolRefAttr::get(value, nestedReferences, getContext());
+}
 
 ArrayAttr Builder::getI32ArrayAttr(ArrayRef<int32_t> values) {
   auto attrs = functional::map(