TypeFinder: prefer iterative algorithm to keep stack usage low.

Introduce subtype_reverse_iterator to maintain
the numbering assigned during the recursive type walk.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@192770 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/Type.h

@@ -324,6 +324,14 @@ class Type {
   subtype_iterator subtype_begin() const { return ContainedTys; }
   subtype_iterator subtype_end() const { return &ContainedTys[NumContainedTys];}
 
+  typedef std::reverse_iterator<subtype_iterator> subtype_reverse_iterator;
+  subtype_reverse_iterator subtype_rbegin() const {
+    return subtype_reverse_iterator(subtype_end());
+  }
+  subtype_reverse_iterator subtype_rend() const {
+    return subtype_reverse_iterator(subtype_begin());
+  }
+
   /// getContainedType - This method is used to implement the type iterator
   /// (defined a the end of the file).  For derived types, this returns the
   /// types 'contained' in the derived type.

lib/IR/TypeFinder.cpp

@@ -94,19 +94,27 @@ void TypeFinder::clear() {
 /// incorporateType - This method adds the type to the list of used structures
 /// if it's not in there already.
 void TypeFinder::incorporateType(Type *Ty) {
-  // Check to see if we're already visited this type.
+  // Check to see if we've already visited this type.
   if (!VisitedTypes.insert(Ty).second)
     return;
 
-  // If this is a structure or opaque type, add a name for the type.
-  if (StructType *STy = dyn_cast<StructType>(Ty))
-    if (!OnlyNamed || STy->hasName())
-      StructTypes.push_back(STy);
-
-  // Recursively walk all contained types.
-  for (Type::subtype_iterator I = Ty->subtype_begin(),
-         E = Ty->subtype_end(); I != E; ++I)
-    incorporateType(*I);
+  SmallVector<Type *, 4> TypeWorklist;
+  TypeWorklist.push_back(Ty);
+  do {
+    Ty = TypeWorklist.pop_back_val();
+
+    // If this is a structure or opaque type, add a name for the type.
+    if (StructType *STy = dyn_cast<StructType>(Ty))
+      if (!OnlyNamed || STy->hasName())
+        StructTypes.push_back(STy);
+
+    // Add all unvisited subtypes to worklist for processing
+    for (Type::subtype_reverse_iterator I = Ty->subtype_rbegin(),
+                                        E = Ty->subtype_rend();
+         I != E; ++I)
+      if (VisitedTypes.insert(*I).second)
+        TypeWorklist.push_back(*I);
+  } while (!TypeWorklist.empty());
 }
 
 /// incorporateValue - This method is used to walk operand lists finding types