Fix Doxygen issues:

* wrap code blocks in \code ... \endcode;
* refer to parameter names in paragraphs correctly (\arg is not what most
  people want -- it starts a new paragraph).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163790 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/CodeGenPrepare.cpp

@@ -662,6 +662,7 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
 /// DupRetToEnableTailCallOpts - Look for opportunities to duplicate return
 /// instructions to the predecessor to enable tail call optimizations. The
 /// case it is currently looking for is:
+/// @code
 /// bb0:
 ///   %tmp0 = tail call i32 @f0()
 ///   br label %return
@@ -674,9 +675,11 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
 /// return:
 ///   %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ]
 ///   ret i32 %retval
+/// @endcode
 ///
 /// =>
 ///
+/// @code
 /// bb0:
 ///   %tmp0 = tail call i32 @f0()
 ///   ret i32 %tmp0
@@ -686,7 +689,7 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
 /// bb2:
 ///   %tmp2 = tail call i32 @f2()
 ///   ret i32 %tmp2
-///
+/// @endcode
 bool CodeGenPrepare::DupRetToEnableTailCallOpts(ReturnInst *RI) {
   if (!TLI)
     return false;