llvm-mc: Add some more doxyments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@74607 91177308-0d34-0410-b5e6-96231b3b80d8

tools/llvm-mc/AsmExpr.h

@@ -18,13 +18,15 @@ class MCContext;
 class MCSymbol;
 class MCValue;
 
+/// AsmExpr - Base class for the full range of assembler expressions which are
+/// needed for parsing.  
 class AsmExpr {
 public:
   enum AsmExprKind {
-    Binary,    /// Binary expressions.
-    Constant,  /// Constant expressions.
-    SymbolRef, /// References to labels and assigned expressions.
-    Unary      /// Unary expressions.
+    Binary,    ///< Binary expressions.
+    Constant,  ///< Constant expressions.
+    SymbolRef, ///< References to labels and assigned expressions.
+    Unary      ///< Unary expressions.
   };
   
 private:
@@ -45,7 +47,7 @@ public:
   bool EvaluateAsAbsolute(MCContext &Ctx, int64_t &Res) const;
 
   /// EvaluateAsRelocatable - Try to evaluate the expression to a relocatable
-  /// value.
+  /// value, i.e. an expression of the fixed form (a - b + constant).
   ///
   /// @param Res - The relocatable value, if evaluation succeeds.
   /// @result - True on success.
@@ -54,6 +56,7 @@ public:
   static bool classof(const AsmExpr *) { return true; }
 };
 
+//// AsmConstantExpr - Represent a constant integer expression.
 class AsmConstantExpr : public AsmExpr {
   int64_t Value;
 
@@ -69,6 +72,12 @@ public:
   static bool classof(const AsmConstantExpr *) { return true; }
 };
 
+/// AsmSymbolRefExpr - Represent a reference to a symbol from inside an
+/// expression.
+///
+/// A symbol reference in an expression may be a use of a label, a use of an
+/// assembler variable (defined constant), or constitute an implicit definition
+/// of the symbol as external.
 class AsmSymbolRefExpr : public AsmExpr {
   MCSymbol *Symbol;
 
@@ -84,13 +93,14 @@ public:
   static bool classof(const AsmSymbolRefExpr *) { return true; }
 };
 
+/// AsmUnaryExpr - Unary assembler expressions.
 class AsmUnaryExpr : public AsmExpr {
 public:
   enum Opcode {
-    LNot,  /// Logical negation.
-    Minus, /// Unary minus.
-    Not,   /// Bit-wise negation.
-    Plus   /// Unary plus.
+    LNot,  ///< Logical negation.
+    Minus, ///< Unary minus.
+    Not,   ///< Bitwise negation.
+    Plus   ///< Unary plus.
   };
 
 private:
@@ -114,27 +124,28 @@ public:
   static bool classof(const AsmUnaryExpr *) { return true; }
 };
 
+/// AsmBinaryExpr - Binary assembler expressions.
 class AsmBinaryExpr : public AsmExpr {
 public:
   enum Opcode {
-    Add,  /// Addition.
-    And,  /// Bitwise and.
-    Div,  /// Division.
-    EQ,   /// Equality comparison.
-    GT,   /// Greater than comparison.
-    GTE,  /// Greater than or equal comparison.
-    LAnd, /// Logical and.
-    LOr,  /// Logical or.
-    LT,   /// Less than comparison.
-    LTE,  /// Less than or equal comparison.
-    Mod,  /// Modulus.
-    Mul,  /// Multiplication.
-    NE,   /// Inequality comparison.
-    Or,   /// Bitwise or.
-    Shl,  /// Bitwise shift left.
-    Shr,  /// Bitwise shift right.
-    Sub,  /// Subtraction.
-    Xor   /// Bitwise exclusive or.
+    Add,  ///< Addition.
+    And,  ///< Bitwise and.
+    Div,  ///< Division.
+    EQ,   ///< Equality comparison.
+    GT,   ///< Greater than comparison.
+    GTE,  ///< Greater than or equal comparison.
+    LAnd, ///< Logical and.
+    LOr,  ///< Logical or.
+    LT,   ///< Less than comparison.
+    LTE,  ///< Less than or equal comparison.
+    Mod,  ///< Modulus.
+    Mul,  ///< Multiplication.
+    NE,   ///< Inequality comparison.
+    Or,   ///< Bitwise or.
+    Shl,  ///< Bitwise shift left.
+    Shr,  ///< Bitwise shift right.
+    Sub,  ///< Subtraction.
+    Xor   ///< Bitwise exclusive or.
   };
 
 private:
@@ -151,7 +162,10 @@ public:
 
   Opcode getOpcode() const { return Op; }
 
+  /// getLHS - Get the left-hand side expression of the binary operator.
   AsmExpr *getLHS() const { return LHS; }
+
+  /// getRHS - Get the right-hand side expression of the binary operator.
   AsmExpr *getRHS() const { return RHS; }
 
   static bool classof(const AsmExpr *E) {