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/* ****************************************************************************
*
* Copyright (c) Microsoft Corporation.
*
* This source code is subject to terms and conditions of the Microsoft Public License. A
* copy of the license can be found in the License.html file at the root of this distribution. If
* you cannot locate the Microsoft Public License, please send an email to
* dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound
* by the terms of the Microsoft Public License.
*
* You must not remove this notice, or any other, from this software.
*
*
* ***************************************************************************/
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq.Expressions;
using System.Runtime.CompilerServices;
using System.Threading;
using Microsoft.Scripting.Generation;
using Microsoft.Scripting.Utils;
namespace Microsoft.Scripting.Interpreter {
/// <summary>
/// Manages creation of interpreted delegates. These delegates will get
/// compiled if they are executed often enough.
/// </summary>
internal sealed class LightDelegateCreator {
private readonly Interpreter _interpreter;
private readonly LambdaExpression _lambda;
private readonly IList<ParameterExpression> _closureVariables;
// Adaptive compilation support:
private Type _compiledDelegateType;
private Delegate _compiled;
private int _executionCount;
private readonly object _compileLock = new object();
private const int CompilationThreshold = 32;
internal LightDelegateCreator(Interpreter interpreter, LambdaExpression lambda, IList<ParameterExpression> closureVariables) {
_interpreter = interpreter;
_lambda = lambda;
_closureVariables = closureVariables;
}
internal IList<ParameterExpression> ClosureVariables {
get { return _closureVariables; }
}
internal Interpreter Interpreter {
get { return _interpreter; }
}
private bool HasClosure {
get { return _closureVariables.Count > 0; }
}
internal bool HasCompiled {
get { return _compiled != null; }
}
/// <summary>
/// true if the compiled delegate has the same type as the lambda;
/// false if the type was changed for interpretation.
/// </summary>
internal bool SameDelegateType {
get { return _compiledDelegateType == _lambda.Type; }
}
internal Delegate CreateDelegate() {
return CreateDelegate(null);
}
internal Delegate CreateDelegate(StrongBox<object>[] closure) {
if (_compiled != null) {
// If the delegate type we want is not a Func/Action, we can't
// use the compiled code directly. So instead just fall through
// and create an interpreted LightLambda, which will pick up
// the compiled delegate on its first run.
//
// Ideally, we would just rebind the compiled delegate using
// Delgate.CreateDelegate. Unfortunately, it doesn't work on
// dynamic methods.
if (SameDelegateType) {
return CreateCompiledDelegate(closure);
}
}
if (_interpreter == null) {
// We can't interpret, so force a compile
Compile(null);
Delegate compiled = CreateCompiledDelegate(closure);
Debug.Assert(compiled.GetType() == _lambda.Type);
return compiled;
}
// Otherwise, we'll create an interpreted LightLambda
return new LightLambda(this, closure).MakeDelegate(_lambda.Type);
}
/// <summary>
/// Used by LightLambda to get the compiled delegate.
/// </summary>
internal Delegate CreateCompiledDelegate(StrongBox<object>[] closure) {
Debug.Assert(HasClosure == (closure != null));
if (HasClosure) {
// We need to apply the closure to get the actual delegate.
var applyClosure = (Func<StrongBox<object>[], Delegate>)_compiled;
return applyClosure(closure);
}
return _compiled;
}
/// <summary>
/// Create a compiled delegate for the LightLambda, and saves it so
/// future calls to Run will execute the compiled code instead of
/// interpreting.
/// </summary>
internal void Compile(object state) {
if (_compiled != null) {
return;
}
// Compilation is expensive, we only want to do it once.
lock (_compileLock) {
if (_compiled != null) {
return;
}
// Interpreter needs a standard delegate type.
// So change the lambda's delegate type to Func<...> or
// Action<...> so it can be called from the LightLambda.Run
// methods.
LambdaExpression lambda = _lambda;
if (_interpreter != null) {
_compiledDelegateType = GetFuncOrAction(lambda);
lambda = Expression.Lambda(_compiledDelegateType, lambda.Body, lambda.Name, lambda.Parameters);
}
if (HasClosure) {
_compiled = LightLambdaClosureVisitor.BindLambda(lambda, _closureVariables);
} else {
_compiled = lambda.Compile();
}
}
}
private static Type GetFuncOrAction(LambdaExpression lambda) {
Type delegateType;
bool isVoid = lambda.ReturnType == typeof(void);
if (isVoid && lambda.Parameters.Count == 2 &&
lambda.Parameters[0].IsByRef && lambda.Parameters[1].IsByRef) {
return typeof(ActionRef<,>).MakeGenericType(lambda.Parameters.Map(p => p.Type));
} else {
Type[] types = lambda.Parameters.Map(p => p.IsByRef ? p.Type.MakeByRefType() : p.Type);
if (isVoid) {
if (Expression.TryGetActionType(types, out delegateType)) {
return delegateType;
}
} else {
types = types.AddLast(lambda.ReturnType);
if (Expression.TryGetFuncType(types, out delegateType)) {
return delegateType;
}
}
return lambda.Type;
}
}
/// <summary>
/// Updates the execution count of this light delegate. If a certain
/// threshold is reached, it will start a background compilation.
/// </summary>
internal void UpdateExecutionCount() {
Debug.Assert(_interpreter != null);
// Don't lock here, it's a frequently hit path.
//
// There could be multiple threads racing, but that is okay.
// Two bad things can happen:
// * We miss increments (one thread sets the counter back)
// * We might enter the "if" branch more than once.
//
// The first is okay, it just means we take longer to compile.
// The second we explicitly guard against inside of Compile().
//
if (++_executionCount >= CompilationThreshold) {
// Kick off the compile on another thread so this one can keep going
ThreadPool.QueueUserWorkItem(Compile, null);
}
}
}
}
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