Documentation: convert WritingAnLLVMBackend.html to reST


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169087 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/CodeGenerator.rst b/docs/CodeGenerator.rst
index e2bbdb5..cafa93e 100644
--- a/docs/CodeGenerator.rst
+++ b/docs/CodeGenerator.rst
@@ -250,6 +250,8 @@
 * various high-level characteristics, like whether it is profitable to turn
   division by a constant into a multiplication sequence.
 
+.. _TargetRegisterInfo:
+
 The ``TargetRegisterInfo`` class
 --------------------------------
 
@@ -771,6 +773,8 @@
 SREM or UREM operation.  The `legalize types`_ and `legalize operations`_ phases
 are responsible for turning an illegal DAG into a legal DAG.
 
+.. _SelectionDAG-Process:
+
 SelectionDAG Instruction Selection Process
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^