Allow targets to select the default scheduler by name.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155090 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachinePassRegistry.cpp b/lib/CodeGen/MachinePassRegistry.cpp
index 58e067b..cb204fd 100644
--- a/lib/CodeGen/MachinePassRegistry.cpp
+++ b/lib/CodeGen/MachinePassRegistry.cpp
@@ -18,6 +18,19 @@
 
 void MachinePassRegistryListener::anchor() { }
 
+/// setDefault - Set the default constructor by name.
+void MachinePassRegistry::setDefault(StringRef Name) {
+  MachinePassCtor Ctor = 0;
+  for(MachinePassRegistryNode *R = getList(); R; R = R->getNext()) {
+    if (R->getName() == Name) {
+      Ctor = R->getCtor();
+      break;
+    }
+  }
+  assert(Ctor && "Unregistered pass name");
+  setDefault(Ctor);
+}
+
 /// Add - Adds a function pass to the registration list.
 ///
 void MachinePassRegistry::Add(MachinePassRegistryNode *Node) {