A small refactoring + adding comments.

SelectionDAGIsel::LowerArguments needs a function, not a basic block. So it
makes sense to pass it the function instead of extracting a basic-block from
the function and then tossing it. This is also more self-documenting (functions
have arguments, BBs don't).

In addition, added comments to a couple of Select* methods.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@176305 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/SelectionDAGISel.h

@@ -249,16 +249,26 @@ private:
                     const SDValue *Ops, unsigned NumOps, unsigned EmitNodeInfo);
 
   void PrepareEHLandingPad();
+
+  /// \brief Perform instruction selection on all basic blocks in the function.
   void SelectAllBasicBlocks(const Function &Fn);
+
+  /// \brief Perform instruction selection on a single basic block, for
+  /// instructions between \p Begin and \p End.  \p HadTailCall will be set
+  /// to true if a call in the block was translated as a tail call.
+  void SelectBasicBlock(BasicBlock::const_iterator Begin,
+                        BasicBlock::const_iterator End,
+                        bool &HadTailCall);
+
   bool TryToFoldFastISelLoad(const LoadInst *LI, const Instruction *FoldInst,
                              FastISel *FastIS);
   void FinishBasicBlock();
 
-  void SelectBasicBlock(BasicBlock::const_iterator Begin,
-                        BasicBlock::const_iterator End,
-                        bool &HadTailCall);
   void CodeGenAndEmitDAG();
-  void LowerArguments(const BasicBlock *BB);
+
+  /// \brief Generate instructions for lowering the incoming arguments of the
+  /// given function.
+  void LowerArguments(const Function &F);
 
   void ComputeLiveOutVRegInfo();