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// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
using System;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
using Mono.Cecil;
using Mono.Cecil.Cil;
namespace Mono.Linker
{
public static class MethodBodyScanner
{
public static bool IsWorthConvertingToThrow (MethodBody body)
{
// Some bodies are cheaper size wise to leave alone than to convert to a throw
Instruction? previousMeaningful = null;
int meaningfulCount = 0;
foreach (var ins in body.Instructions) {
// Handle ignoring noops because because (1) it's a valid case to ignore
// and (2) When running the tests on .net core roslyn tosses in no ops
// and that leads to a difference in test results between mcs and .net framework csc.
if (ins.OpCode.Code == Code.Nop)
continue;
meaningfulCount++;
if (meaningfulCount == 1 && ins.OpCode.Code == Code.Ret)
return false;
if (meaningfulCount == 2 && ins.OpCode.Code == Code.Ret && previousMeaningful != null) {
if (previousMeaningful.OpCode.StackBehaviourPop == StackBehaviour.Pop0) {
switch (previousMeaningful.OpCode.StackBehaviourPush) {
case StackBehaviour.Pushi:
case StackBehaviour.Pushi8:
case StackBehaviour.Pushr4:
case StackBehaviour.Pushr8:
return false;
}
switch (previousMeaningful.OpCode.Code) {
case Code.Ldnull:
return false;
}
}
}
if (meaningfulCount >= 2)
return true;
previousMeaningful = ins;
}
return true;
}
}
readonly struct InterfacesOnStackScanner
{
readonly LinkContext context;
public InterfacesOnStackScanner (LinkContext context)
{
this.context = context;
}
public IEnumerable<(InterfaceImplementation, TypeDefinition)>? GetReferencedInterfaces (MethodBody body)
{
var possibleStackTypes = AllPossibleStackTypes (body.Method);
if (possibleStackTypes.Count == 0)
return null;
var interfaceTypes = possibleStackTypes.Where (t => t.IsInterface).ToArray ();
if (interfaceTypes.Length == 0)
return null;
var interfaceImplementations = new HashSet<(InterfaceImplementation, TypeDefinition)> ();
// If a type could be on the stack in the body and an interface it implements could be on the stack on the body
// then we need to mark that interface implementation. When this occurs it is not safe to remove the interface implementation from the type
// even if the type is never instantiated
foreach (var type in possibleStackTypes) {
// We only sweep interfaces on classes so that's why we only care about classes
if (!type.IsClass)
continue;
TypeDefinition? currentType = type;
while (currentType?.BaseType != null) // Checking BaseType != null to skip System.Object
{
AddMatchingInterfaces (interfaceImplementations, currentType, interfaceTypes);
currentType = context.TryResolve (currentType.BaseType);
}
}
return interfaceImplementations;
}
HashSet<TypeDefinition> AllPossibleStackTypes (MethodDefinition method)
{
if (!method.HasBody)
throw new ArgumentException ("Method does not have body", nameof (method));
var body = method.Body;
var types = new HashSet<TypeDefinition> ();
foreach (VariableDefinition var in body.Variables)
AddIfResolved (types, var.VariableType);
foreach (var param in method.GetParameters ())
AddIfResolved (types, param.ParameterType);
foreach (ExceptionHandler eh in body.ExceptionHandlers) {
if (eh.HandlerType == ExceptionHandlerType.Catch) {
AddIfResolved (types, eh.CatchType);
}
}
foreach (Instruction instruction in body.Instructions) {
if (instruction.Operand is FieldReference fieldReference) {
if (context.TryResolve (fieldReference)?.FieldType is TypeReference fieldType)
AddIfResolved (types, fieldType);
} else if (instruction.Operand is MethodReference methodReference) {
if (methodReference is GenericInstanceMethod genericInstanceMethod)
AddFromGenericInstance (types, genericInstanceMethod);
if (methodReference.DeclaringType is GenericInstanceType genericInstanceType)
AddFromGenericInstance (types, genericInstanceType);
var resolvedMethod = context.TryResolve (methodReference);
if (resolvedMethod != null) {
if (resolvedMethod.HasMetadataParameters ()) {
foreach (var param in resolvedMethod.GetParameters ())
AddIfResolved (types, param.ParameterType);
}
AddFromGenericParameterProvider (types, resolvedMethod);
AddFromGenericParameterProvider (types, resolvedMethod.DeclaringType);
AddIfResolved (types, resolvedMethod.ReturnType);
}
}
}
return types;
}
void AddMatchingInterfaces (HashSet<(InterfaceImplementation, TypeDefinition)> results, TypeDefinition type, TypeDefinition[] interfaceTypes)
{
if (!type.HasInterfaces)
return;
foreach (var interfaceType in interfaceTypes) {
if (HasInterface (type, interfaceType, out InterfaceImplementation? implementation))
results.Add ((implementation, type));
}
}
bool HasInterface (TypeDefinition type, TypeDefinition interfaceType, [NotNullWhen (true)] out InterfaceImplementation? implementation)
{
implementation = null;
if (!type.HasInterfaces)
return false;
foreach (var iface in type.Interfaces) {
if (context.TryResolve (iface.InterfaceType) == interfaceType) {
implementation = iface;
return true;
}
}
return false;
}
void AddFromGenericInstance (HashSet<TypeDefinition> set, IGenericInstance instance)
{
if (!instance.HasGenericArguments)
return;
foreach (var genericArgument in instance.GenericArguments)
AddIfResolved (set, genericArgument);
}
void AddFromGenericParameterProvider (HashSet<TypeDefinition> set, IGenericParameterProvider provider)
{
if (!provider.HasGenericParameters)
return;
foreach (var genericParameter in provider.GenericParameters) {
foreach (var constraint in genericParameter.Constraints)
AddIfResolved (set, constraint.ConstraintType);
}
}
void AddIfResolved (HashSet<TypeDefinition> set, TypeReference item)
{
var resolved = context.TryResolve (item);
if (resolved == null)
return;
set.Add (resolved);
}
}
}
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