C# EmitContext.MarkLabel方法代码示例

        public override void Emit(EmitContext ec)
        {
            Label is_null_label = ec.DefineLabel ();
            Label end_label = ec.DefineLabel ();

            unwrap.EmitCheck (ec);
            ec.Emit (OpCodes.Brfalse, is_null_label);

            expr.Emit (ec);

            ec.Emit (OpCodes.Br, end_label);
            ec.MarkLabel (is_null_label);

            null_value.Emit (ec);
            ec.MarkLabel (end_label);
        }

		public override void Emit (EmitContext ec)
		{
			//
			// Optimize same expression operation
			//
			if (right_unwrap != null && right.Equals (left))
				right_unwrap = left_unwrap;

			if (user_operator == null && IsBitwiseBoolean) {
				EmitBitwiseBoolean (ec);
				return;
			}

			if ((Oper & Operator.EqualityMask) != 0) {
				EmitEquality (ec);
				return;
			}

			Label is_null_label = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();

			if (left_unwrap != null) {
				left_unwrap.EmitCheck (ec);
				ec.Emit (OpCodes.Brfalse, is_null_label);
			}

			//
			// Don't emit HasValue check when left and right expressions are same
			//
			if (right_unwrap != null && !left.Equals (right)) {
				right_unwrap.EmitCheck (ec);
				ec.Emit (OpCodes.Brfalse, is_null_label);
			}

			EmitOperator (ec, left.Type);

			if (wrap_ctor != null)
				ec.Emit (OpCodes.Newobj, wrap_ctor);

			ec.Emit (OpCodes.Br_S, end_label);
			ec.MarkLabel (is_null_label);

			if ((Oper & Operator.ComparisonMask) != 0) {
				ec.Emit (OpCodes.Ldc_I4_0);
			} else {
				LiftedNull.Create (type, loc).Emit (ec);
			}

			ec.MarkLabel (end_label);
		}

		//
		// Emits optimized equality or inequality operator when possible
		//
		void EmitEquality (EmitContext ec)
		{
			//
			// Either left or right is null
			//
			if (left_unwrap != null && (IsRightNullLifted || right.IsNull)) {
				left_unwrap.EmitCheck (ec);
				if (Oper == Binary.Operator.Equality) {
					ec.Emit (OpCodes.Ldc_I4_0);
					ec.Emit (OpCodes.Ceq);
				}
				return;
			}

			if (right_unwrap != null && (IsLeftNullLifted || left.IsNull)) {
				right_unwrap.EmitCheck (ec);
				if (Oper == Binary.Operator.Equality) {
					ec.Emit (OpCodes.Ldc_I4_0);
					ec.Emit (OpCodes.Ceq);
				}
				return;
			}

			Label dissimilar_label = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();

			if (user_operator != null) {
				user_operator.Emit (ec);
				ec.Emit (Oper == Operator.Equality ? OpCodes.Brfalse_S : OpCodes.Brtrue_S, dissimilar_label);
			} else {
				left.Emit (ec);
				right.Emit (ec);

				ec.Emit (OpCodes.Bne_Un_S, dissimilar_label);
			}

			if (left_unwrap != null)
				left_unwrap.EmitCheck (ec);

			if (right_unwrap != null)
				right_unwrap.EmitCheck (ec);

			if (left_unwrap != null && right_unwrap != null) {
				if (Oper == Operator.Inequality)
					ec.Emit (OpCodes.Xor);
				else
					ec.Emit (OpCodes.Ceq);
			} else {
				if (Oper == Operator.Inequality) {
					ec.Emit (OpCodes.Ldc_I4_0);
					ec.Emit (OpCodes.Ceq);
				}
			}

			ec.Emit (OpCodes.Br_S, end_label);

			ec.MarkLabel (dissimilar_label);
			if (Oper == Operator.Inequality)
				ec.Emit (OpCodes.Ldc_I4_1);
			else
				ec.Emit (OpCodes.Ldc_I4_0);

			ec.MarkLabel (end_label);
		}

		void EmitBitwiseBoolean (EmitContext ec)
		{
			Label load_left = ec.DefineLabel ();
			Label load_right = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();

			// null & value, null | value
			if (left_unwrap == null) {
				left_unwrap = right_unwrap;
				right_unwrap = null;
				right = left;
			}

			left_unwrap.Emit (ec);
			ec.Emit (OpCodes.Brtrue_S, load_right);

			// value & null, value | null
			if (right_unwrap != null) {
				right_unwrap.Emit (ec);
				ec.Emit (OpCodes.Brtrue_S, load_left);
			}

			left_unwrap.EmitCheck (ec);
			ec.Emit (OpCodes.Brfalse_S, load_right);

			// load left
			ec.MarkLabel (load_left);

			if (Oper == Operator.BitwiseAnd) {
				left_unwrap.Load (ec);
			} else {
				if (right_unwrap == null) {
					right.Emit (ec);
					if (right is EmptyConstantCast || right is EmptyCast)
						ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
				} else {
					right_unwrap.Load (ec);
					right_unwrap = left_unwrap;
				}
			}
			ec.Emit (OpCodes.Br_S, end_label);

			// load right
			ec.MarkLabel (load_right);
			if (right_unwrap == null) {
				if (Oper == Operator.BitwiseAnd) {
					right.Emit (ec);
					if (right is EmptyConstantCast || right is EmptyCast)
						ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
				} else {
					left_unwrap.Load (ec);
				}
			} else {
				right_unwrap.Load (ec);
			}

			ec.MarkLabel (end_label);
		}

		void DoEmit (EmitContext ec, bool is_expr)
		{
			Label is_null_label = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();

			unwrap.EmitCheck (ec);
			ec.Emit (OpCodes.Brfalse, is_null_label);

			if (is_expr) {
				underlying.Emit (ec);
				ec.Emit (OpCodes.Br_S, end_label);
			} else {
				underlying.EmitStatement (ec);
			}

			ec.MarkLabel (is_null_label);
			if (is_expr)
				LiftedNull.Create (type, loc).Emit (ec);

			ec.MarkLabel (end_label);
		}

		//
		// Emits optimized equality or inequality operator when possible
		//
		void EmitEquality (EmitContext ec)
		{
			//
			// Either left or right is null
			// 
			if (UnwrapLeft != null && Binary.Right.IsNull) { // TODO: Optimize for EmitBranchable
				//
				// left.HasValue == false 
				//
				UnwrapLeft.EmitCheck (ec);
				if (Binary.Oper == Binary.Operator.Equality) {
					ec.EmitInt (0);
					ec.Emit (OpCodes.Ceq);
				}
				return;
			}

			if (UnwrapRight != null && Binary.Left.IsNull) {
				//
				// right.HasValue == false 
				//
				UnwrapRight.EmitCheck (ec);
				if (Binary.Oper == Binary.Operator.Equality) {
					ec.EmitInt (0);
					ec.Emit (OpCodes.Ceq);
				}
				return;
			}

			Label dissimilar_label = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();

			if (UserOperator != null) {
				var left = Left;

				if (UnwrapLeft != null) {
					UnwrapLeft.EmitCheck (ec);
				} else {
					// Keep evaluation order same
					if (!(Left is VariableReference)) {
						Left.Emit (ec);
						var lt = new LocalTemporary (Left.Type);
						lt.Store (ec);
						left = lt;
					}
				}

				if (UnwrapRight != null) {
					UnwrapRight.EmitCheck (ec);

					if (UnwrapLeft != null) {
						ec.Emit (OpCodes.Bne_Un, dissimilar_label);

						Label compare_label = ec.DefineLabel ();
						UnwrapLeft.EmitCheck (ec);
						ec.Emit (OpCodes.Brtrue, compare_label);

						if (Binary.Oper == Binary.Operator.Equality)
							ec.EmitInt (1);
						else
							ec.EmitInt (0);

						ec.Emit (OpCodes.Br, end_label);

						ec.MarkLabel (compare_label);
					} else {
						ec.Emit (OpCodes.Brfalse, dissimilar_label);
					}
				} else {
					ec.Emit (OpCodes.Brfalse, dissimilar_label);
				}

				var args = new Arguments (2);
				args.Add (new Argument (left));
				args.Add (new Argument (Right));

				var call = new CallEmitter ();
				call.EmitPredefined (ec, UserOperator, args);
			} else {
				if (ec.HasSet (BuilderContext.Options.AsyncBody) && Binary.Right.ContainsEmitWithAwait ()) {
					Left = Left.EmitToField (ec);
					Right = Right.EmitToField (ec);
				}

				//
				// Emit underlying value comparison first.
				//
				// For this code: int? a = 1; bool b = a == 1;
				//
				// We emit something similar to this. Expressions with side effects have local
				// variable created by Unwrap expression
				//
				//	left.GetValueOrDefault ()
				//	right
				//	bne.un.s   dissimilar_label
				//  left.HasValue
				//	br.s       end_label
//.........这里部分代码省略.........

		void EmitBitwiseBoolean (EmitContext ec)
		{
			Label load_left = ec.DefineLabel ();
			Label load_right = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();
			Label is_null_label = ec.DefineLabel ();

			bool or = Binary.Oper == Binary.Operator.BitwiseOr;

			//
			// Both operands are bool? types
			//
			if (UnwrapLeft != null && UnwrapRight != null) {
				if (ec.HasSet (BuilderContext.Options.AsyncBody) && Binary.Right.ContainsEmitWithAwait ()) {
					Left = Left.EmitToField (ec);
					Right = Right.EmitToField (ec);
				}

				Left.Emit (ec);
				ec.Emit (OpCodes.Brtrue_S, load_right);

				Right.Emit (ec);
				ec.Emit (OpCodes.Brtrue_S, load_left);

				UnwrapLeft.EmitCheck (ec);
				ec.Emit (OpCodes.Brfalse_S, load_right);

				// load left
				ec.MarkLabel (load_left);
				if (or)
					UnwrapRight.Load (ec);
				else
					UnwrapLeft.Load (ec);

				ec.Emit (OpCodes.Br_S, end_label);

				// load right
				ec.MarkLabel (load_right);
				if (or)
					UnwrapLeft.Load (ec);
				else
					UnwrapRight.Load (ec);

				ec.MarkLabel (end_label);
				return;
			}

			//
			// Faster version when one operand is bool
			//
			if (UnwrapLeft == null) {
				//
				// (bool, bool?)
				//
				// Optimizes remaining (false & bool?), (true | bool?) which are not easy to handle
				// in binary expression reduction
				//
				var c = Left as BoolConstant;
				if (c != null) {
					// Keep evaluation order
					UnwrapRight.Store (ec);

					ec.EmitInt (or ? 1 : 0);
					ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
				} else if (Left.IsNull) {
					UnwrapRight.Emit (ec);
					ec.Emit (or ? OpCodes.Brfalse_S : OpCodes.Brtrue_S, is_null_label);

					UnwrapRight.Load (ec);
					ec.Emit (OpCodes.Br_S, end_label);

					ec.MarkLabel (is_null_label);
					LiftedNull.Create (type, loc).Emit (ec);
				} else {
					Left.Emit (ec);
					ec.Emit (or ? OpCodes.Brfalse_S : OpCodes.Brtrue_S, load_right);

					ec.EmitInt (or ? 1 : 0);
					ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));

					ec.Emit (OpCodes.Br_S, end_label);

					ec.MarkLabel (load_right);
					UnwrapRight.Original.Emit (ec);
				}
			} else {
				//
				// (bool?, bool)
				//
				// Keep left-right evaluation order
				UnwrapLeft.Store (ec);

				//
				// Optimizes remaining (bool? & false), (bool? | true) which are not easy to handle
				// in binary expression reduction
				//
				var c = Right as BoolConstant;
				if (c != null) {
					ec.EmitInt (or ? 1 : 0);
					ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
//.........这里部分代码省略.........

		public override void Emit (EmitContext ec)
		{
			if (IsBitwiseBoolean && UserOperator == null) {
				EmitBitwiseBoolean (ec);
				return;
			}

			if ((Binary.Oper & Binary.Operator.EqualityMask) != 0) {
				EmitEquality (ec);
				return;
			}

			Label is_null_label = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();

			if (ec.HasSet (BuilderContext.Options.AsyncBody) && Right.ContainsEmitWithAwait ()) {
				Left = Left.EmitToField (ec);
				Right = Right.EmitToField (ec);
			}

			if (UnwrapLeft != null) {
				UnwrapLeft.EmitCheck (ec);
			}

			//
			// Don't emit HasValue check when left and right expressions are same
			//
			if (UnwrapRight != null && !Binary.Left.Equals (Binary.Right)) {
				UnwrapRight.EmitCheck (ec);
				if (UnwrapLeft != null) {
					ec.Emit (OpCodes.And);
				}
			}

			ec.Emit (OpCodes.Brfalse, is_null_label);

			if (UserOperator != null) {
				var args = new Arguments (2);
				args.Add (new Argument (Left));
				args.Add (new Argument (Right));

				var call = new CallEmitter ();
				call.EmitPredefined (ec, UserOperator, args);
			} else {
				Binary.EmitOperator (ec, Left, Right);
			}

			//
			// Wrap the result when the operator return type is nullable type
			//
			if (type.IsNullableType)
				ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));

			ec.Emit (OpCodes.Br_S, end_label);
			ec.MarkLabel (is_null_label);

			if ((Binary.Oper & Binary.Operator.ComparisonMask) != 0) {
				ec.EmitInt (0);
			} else {
				LiftedNull.Create (type, loc).Emit (ec);
			}

			ec.MarkLabel (end_label);
		}

		protected override void EmitOperation (EmitContext ec)
		{
			Label is_null_label = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();

			LocalTemporary lt = new LocalTemporary (type);

			// Value is on the stack
			lt.Store (ec);

			var call = new CallEmitter ();
			call.InstanceExpression = lt;
			call.EmitPredefined (ec, NullableInfo.GetHasValue (expr.Type), null);

			ec.Emit (OpCodes.Brfalse, is_null_label);

			call = new CallEmitter ();
			call.InstanceExpression = lt;
			call.EmitPredefined (ec, NullableInfo.GetGetValueOrDefault (expr.Type), null);

			lt.Release (ec);

			base.EmitOperation (ec);

			ec.Emit (OpCodes.Newobj, NullableInfo.GetConstructor (type));
			ec.Emit (OpCodes.Br_S, end_label);

			ec.MarkLabel (is_null_label);
			LiftedNull.Create (type, loc).Emit (ec);

			ec.MarkLabel (end_label);
		}

		void EmitBitwiseBoolean (EmitContext ec)
		{
			Label load_left = ec.DefineLabel ();
			Label load_right = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();

			left_unwrap.Emit (ec);
			ec.Emit (OpCodes.Brtrue_S, load_right);

			right_unwrap.Emit (ec);
			ec.Emit (OpCodes.Brtrue_S, load_left);

			left_unwrap.EmitCheck (ec);
			ec.Emit (OpCodes.Brfalse_S, load_right);

			// load left
			ec.MarkLabel (load_left);

			if (Oper == Operator.BitwiseAnd) {
				left_unwrap.Load (ec);
			} else {
				right_unwrap.Load (ec);
				right_unwrap = left_unwrap;
			}
			ec.Emit (OpCodes.Br_S, end_label);

			// load right
			ec.MarkLabel (load_right);
			right_unwrap.Load (ec);

			ec.MarkLabel (end_label);
		}

		//
		// Emits optimized equality or inequality operator when possible
		//
		void EmitEquality (EmitContext ec)
		{
			//
			// Either left or right is null
			//
			if (left_unwrap != null && (IsRightNullLifted || right.IsNull)) {
				left_unwrap.EmitCheck (ec);
				if (Oper == Binary.Operator.Equality) {
					ec.EmitInt (0);
					ec.Emit (OpCodes.Ceq);
				}
				return;
			}

			if (right_unwrap != null && (IsLeftNullLifted || left.IsNull)) {
				right_unwrap.EmitCheck (ec);
				if (Oper == Binary.Operator.Equality) {
					ec.EmitInt (0);
					ec.Emit (OpCodes.Ceq);
				}
				return;
			}

			Label dissimilar_label = ec.DefineLabel ();
			Label end_label = ec.DefineLabel ();

			if (user_operator != null) {
				user_operator.Emit (ec);
				ec.Emit (Oper == Operator.Equality ? OpCodes.Brfalse_S : OpCodes.Brtrue_S, dissimilar_label);
			} else {
				if (ec.HasSet (BuilderContext.Options.AsyncBody) && right.ContainsEmitWithAwait ()) {
					left = left.EmitToField (ec);
					right = right.EmitToField (ec);
				}

				left.Emit (ec);
				right.Emit (ec);

				ec.Emit (OpCodes.Bne_Un_S, dissimilar_label);
			}

			if (left_unwrap != null)
				left_unwrap.EmitCheck (ec);

			if (right_unwrap != null)
				right_unwrap.EmitCheck (ec);

			if (left_unwrap != null && right_unwrap != null) {
				if (Oper == Operator.Inequality)
					ec.Emit (OpCodes.Xor);
				else
					ec.Emit (OpCodes.Ceq);
			} else {
				if (Oper == Operator.Inequality) {
					ec.EmitInt (0);
					ec.Emit (OpCodes.Ceq);
				}
			}

			ec.Emit (OpCodes.Br_S, end_label);

			ec.MarkLabel (dissimilar_label);
			if (Oper == Operator.Inequality)
				ec.EmitInt (1);
			else
				ec.EmitInt (0);

			ec.MarkLabel (end_label);
		}

		public override void Emit (EmitContext ec)
		{
			Label end_label = ec.DefineLabel ();

			if (unwrap != null) {
				Label is_null_label = ec.DefineLabel ();

				unwrap.EmitCheck (ec);
				ec.Emit (OpCodes.Brfalse, is_null_label);

				//
				// When both expressions are nullable the unwrap
				// is needed only for null check not for value uwrap
				//
				if (type.IsNullableType && TypeSpecComparer.IsEqual (NullableInfo.GetUnderlyingType (type), unwrap.Type))
					unwrap.Load (ec);
				else
					left.Emit (ec);

				ec.Emit (OpCodes.Br, end_label);

				ec.MarkLabel (is_null_label);
				right.Emit (ec);

				ec.MarkLabel (end_label);
				return;
			}

			//
			// Null check is done on original expression not after expression is converted to
			// result type. This is in most cases same but when user conversion is involved
			// we can end up in situation when user operator does the null handling which is
			// not what the operator is supposed to do.
			// There is tricky case where cast of left expression is meant to be cast of
			// whole source expression (null check is done on it) and cast from right-to-left
			// conversion needs to do null check on unconverted source expression.
			//
			if (user_conversion_left) {
				var op_expr = (UserCast) left;

				op_expr.Source.Emit (ec);
				LocalTemporary temp;

				// TODO: More load kinds can be special cased
				if (!(op_expr.Source is VariableReference)) {
					temp = new LocalTemporary (op_expr.Source.Type);
					temp.Store (ec);
					temp.Emit (ec);
					op_expr.Source = temp;
				} else {
					temp = null;
				}

				var right_label = ec.DefineLabel ();
				ec.Emit (OpCodes.Brfalse_S, right_label);
				left.Emit (ec);
				ec.Emit (OpCodes.Br, end_label);
				ec.MarkLabel (right_label);

				if (temp != null)
					temp.Release (ec);
			} else {
				//
				// Common case where expression is not modified before null check and
				// we generate better/smaller code
				//
				left.Emit (ec);
				ec.Emit (OpCodes.Dup);

				// Only to make verifier happy
				if (left.Type.IsGenericParameter)
					ec.Emit (OpCodes.Box, left.Type);

				ec.Emit (OpCodes.Brtrue, end_label);

				ec.Emit (OpCodes.Pop);
			}

			right.Emit (ec);

			ec.MarkLabel (end_label);
		}

		public override void Emit (EmitContext ec)
		{
			Label end_label = ec.DefineLabel ();

			if (unwrap != null) {
				Label is_null_label = ec.DefineLabel ();

				unwrap.EmitCheck (ec);
				ec.Emit (OpCodes.Brfalse, is_null_label);

				//
				// When both expressions are nullable the unwrap
				// is needed only for null check not for value uwrap
				//
				if (type.IsNullableType)
					unwrap.Load (ec);
				else
					left.Emit (ec);

				ec.Emit (OpCodes.Br, end_label);

				ec.MarkLabel (is_null_label);
				right.Emit (ec);

				ec.MarkLabel (end_label);
				return;
			}

			left.Emit (ec);
			ec.Emit (OpCodes.Dup);

			// Only to make verifier happy
			if (left.Type.IsGenericParameter)
				ec.Emit (OpCodes.Box, left.Type);

			ec.Emit (OpCodes.Brtrue, end_label);

			ec.Emit (OpCodes.Pop);
			right.Emit (ec);

			ec.MarkLabel (end_label);
		}