[TableGen] Replace InfoByHwMode::getAsString with writeToStream

Also add operator<< for use with raw_ostream to InfoByHwMode and its
derived classes.

Recommitting r313989 with the fix for unresolved references: explicitly
define the operator<< in namespace llvm.

llvm-svn: 314004
diff --git a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
index ed2ea75..6321c96 100644
--- a/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
+++ b/llvm/utils/TableGen/CodeGenDAGPatterns.cpp
@@ -238,10 +238,16 @@
   return true;
 }
 
+namespace llvm {
+  raw_ostream &operator<<(raw_ostream &OS, const TypeSetByHwMode &T) {
+    T.writeToStream(OS);
+    return OS;
+  }
+}
+
 LLVM_DUMP_METHOD
 void TypeSetByHwMode::dump() const {
-  writeToStream(dbgs());
-  dbgs() << '\n';
+  dbgs() << *this << '\n';
 }
 
 bool TypeSetByHwMode::intersect(SetType &Out, const SetType &In) {