[mlir] Make overloads of SymbolTable::replaceAllSymbolUses consistent.

This function has several overloads that allow to specify the symbol
that should be renamed and the scope for that renaming in different
ways. The overloads were inconsistent in the following way (quoted
strings are `StringAttr`s, other variables are `Operation *`):

* `replaceAllSymbolUses(symbolOp, "new_symbol", scopeOp)` would traverse
  into the symbol table of `scopeOp`.
* `replaceAllSymbolUses("symbol", "new_symbol", scopeOp)` would *not*
  traverse into the symbol table of `scopeOp`.

The underlying behavior was spread over different places and is somewhat
hard to understand. The two overloads above mainly differed by what
`collectSymbolScopes` computed, which is itself overloaded. If `scopeOp`
is a top-level module, then the overload on
`(Operation *, Operation *)`, which is used in the first of the above
cases, computes a scope where the body region of the module is the
`limit`; however, the overload on `(StringAttr, Operation *)` computed
the module op itself as the `limit`. Later, `walkSymbolTable` would walk
the body of the module if it was given as a region but it would *not*
enter the regions of the module op because that op has a symbol table
(which was assumed to be a *different* scope).

The fix in this commit is change the behavior of `collectSymbolScopes`
such that the `(StringAttr, Operation *)` overload returns a scope for
each region in the `limit` argument.

Author: ingomueller-net

mlir/lib/IR/SymbolTable.cpp

@@ -655,12 +655,20 @@ static SmallVector<SymbolScope, 2> collectSymbolScopes(Operation *symbol,
     scopes.back().limit = limit;
   return scopes;
 }
-template <typename IRUnit>
 static SmallVector<SymbolScope, 1> collectSymbolScopes(StringAttr symbol,
-                                                       IRUnit *limit) {
+                                                       Region *limit) {
   return {{SymbolRefAttr::get(symbol), limit}};
 }
 
+static SmallVector<SymbolScope, 1> collectSymbolScopes(StringAttr symbol,
+                                                       Operation *limit) {
+  SmallVector<SymbolScope, 1> scopes;
+  auto symbolRef = SymbolRefAttr::get(symbol);
+  for (auto &region : limit->getRegions())
+    scopes.push_back({symbolRef, &region});
+  return scopes;
+}
+
 /// Returns true if the given reference 'SubRef' is a sub reference of the
 /// reference 'ref', i.e. 'ref' is a further qualified reference.
 static bool isReferencePrefixOf(SymbolRefAttr subRef, SymbolRefAttr ref) {

mlir/test/python/ir/symbol_table.py

@@ -106,9 +106,9 @@ def testSymbolTableRAUW():
       """
         )
         foo, bar = list(m.operation.regions[0].blocks[0].operations)[0:2]
+
+        # Do renaming just within `foo`.
         SymbolTable.set_symbol_name(bar, "bam")
-        # Note that module.operation counts as a "nested symbol table" which won't
-        # be traversed into, so it is necessary to traverse its children.
         SymbolTable.replace_all_symbol_uses("bar", "bam", foo)
         # CHECK: call @bam()
         # CHECK: func private @bam
@@ -118,6 +118,17 @@ def testSymbolTableRAUW():
         print(f"Foo symbol: {repr(SymbolTable.get_symbol_name(foo))}")
         print(f"Bar symbol: {repr(SymbolTable.get_symbol_name(bar))}")
 
+        # Do renaming within the module.
+        SymbolTable.set_symbol_name(bar, "baz")
+        SymbolTable.replace_all_symbol_uses("bam", "baz", m.operation)
+        # CHECK: call @baz()
+        # CHECK: func private @baz
+        print(m)
+        # CHECK: Foo symbol: StringAttr("foo")
+        # CHECK: Bar symbol: StringAttr("baz")
+        print(f"Foo symbol: {repr(SymbolTable.get_symbol_name(foo))}")
+        print(f"Bar symbol: {repr(SymbolTable.get_symbol_name(bar))}")
+
 
 # CHECK-LABEL: testSymbolTableVisibility
 @run