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PeepholeTransform.cs
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PeepholeTransform.cs
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// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
// This code is distributed under MIT X11 license (for details please see \doc\license.txt)
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using ICSharpCode.NRefactory.Utils;
using Mono.Cecil;
namespace ICSharpCode.Decompiler.ILAst
{
public partial class ILAstOptimizer
{
#region TransformDecimalCtorToConstant
static bool TransformDecimalCtorToConstant(List<ILNode> body, ILExpression expr, int pos)
{
MethodReference r;
List<ILExpression> args;
if (expr.Match(ILCode.Newobj, out r, out args) &&
r.DeclaringType.Namespace == "System" &&
r.DeclaringType.Name == "Decimal")
{
if (args.Count == 1) {
int val;
if (args[0].Match(ILCode.Ldc_I4, out val)) {
expr.Code = ILCode.Ldc_Decimal;
expr.Operand = new decimal(val);
expr.InferredType = r.DeclaringType;
expr.Arguments.Clear();
return true;
}
} else if (args.Count == 5) {
int lo, mid, hi, isNegative, scale;
if (expr.Arguments[0].Match(ILCode.Ldc_I4, out lo) &&
expr.Arguments[1].Match(ILCode.Ldc_I4, out mid) &&
expr.Arguments[2].Match(ILCode.Ldc_I4, out hi) &&
expr.Arguments[3].Match(ILCode.Ldc_I4, out isNegative) &&
expr.Arguments[4].Match(ILCode.Ldc_I4, out scale))
{
expr.Code = ILCode.Ldc_Decimal;
expr.Operand = new decimal(lo, mid, hi, isNegative != 0, (byte)scale);
expr.InferredType = r.DeclaringType;
expr.Arguments.Clear();
return true;
}
}
}
bool modified = false;
foreach(ILExpression arg in expr.Arguments) {
modified |= TransformDecimalCtorToConstant(null, arg, -1);
}
return modified;
}
#endregion
#region SimplifyLdObjAndStObj
static bool SimplifyLdObjAndStObj(List<ILNode> body, ILExpression expr, int pos)
{
bool modified = false;
expr = SimplifyLdObjAndStObj(expr, ref modified);
if (modified && body != null)
body[pos] = expr;
for (int i = 0; i < expr.Arguments.Count; i++) {
expr.Arguments[i] = SimplifyLdObjAndStObj(expr.Arguments[i], ref modified);
modified |= SimplifyLdObjAndStObj(null, expr.Arguments[i], -1);
}
return modified;
}
static ILExpression SimplifyLdObjAndStObj(ILExpression expr, ref bool modified)
{
if (expr.Code == ILCode.Initobj) {
expr.Code = ILCode.Stobj;
expr.Arguments.Add(new ILExpression(ILCode.DefaultValue, expr.Operand));
modified = true;
}
ILExpression arg, arg2;
TypeReference type;
ILCode? newCode = null;
if (expr.Match(ILCode.Stobj, out type, out arg, out arg2)) {
switch (arg.Code) {
case ILCode.Ldelema: newCode = ILCode.Stelem_Any; break;
case ILCode.Ldloca: newCode = ILCode.Stloc; break;
case ILCode.Ldflda: newCode = ILCode.Stfld; break;
case ILCode.Ldsflda: newCode = ILCode.Stsfld; break;
}
} else if (expr.Match(ILCode.Ldobj, out type, out arg)) {
switch (arg.Code) {
case ILCode.Ldelema: newCode = ILCode.Ldelem_Any; break;
case ILCode.Ldloca: newCode = ILCode.Ldloc; break;
case ILCode.Ldflda: newCode = ILCode.Ldfld; break;
case ILCode.Ldsflda: newCode = ILCode.Ldsfld; break;
}
}
if (newCode != null) {
arg.Code = newCode.Value;
if (expr.Code == ILCode.Stobj) {
arg.InferredType = expr.InferredType;
arg.ExpectedType = expr.ExpectedType;
arg.Arguments.Add(arg2);
}
arg.ILRanges.AddRange(expr.ILRanges);
modified = true;
return arg;
} else {
return expr;
}
}
#endregion
#region SimplifyLdcI4ConvI8
static bool SimplifyLdcI4ConvI8(List<ILNode> body, ILExpression expr, int pos)
{
ILExpression ldc;
int val;
if (expr.Match(ILCode.Conv_I8, out ldc) && ldc.Match(ILCode.Ldc_I4, out val)) {
expr.Code = ILCode.Ldc_I8;
expr.Operand = (long)val;
expr.Arguments.Clear();
return true;
}
bool modified = false;
foreach(ILExpression arg in expr.Arguments) {
modified |= SimplifyLdcI4ConvI8(null, arg, -1);
}
return modified;
}
#endregion
#region CachedDelegateInitialization
void CachedDelegateInitialization(ILBlock block, ref int i)
{
// if (logicnot(ldsfld(field))) {
// stsfld(field, newobj(Action::.ctor, ldnull(), ldftn(method)))
// } else {
// }
// ...(..., ldsfld(field), ...)
ILCondition c = block.Body[i] as ILCondition;
if (c == null || c.Condition == null && c.TrueBlock == null || c.FalseBlock == null)
return;
if (!(c.TrueBlock.Body.Count == 1 && c.FalseBlock.Body.Count == 0))
return;
if (!c.Condition.Match(ILCode.LogicNot))
return;
ILExpression condition = c.Condition.Arguments.Single() as ILExpression;
if (condition == null || condition.Code != ILCode.Ldsfld)
return;
FieldDefinition field = ((FieldReference)condition.Operand).ResolveWithinSameModule(); // field is defined in current assembly
if (field == null || !field.IsCompilerGeneratedOrIsInCompilerGeneratedClass())
return;
ILExpression stsfld = c.TrueBlock.Body[0] as ILExpression;
if (!(stsfld != null && stsfld.Code == ILCode.Stsfld && ((FieldReference)stsfld.Operand).ResolveWithinSameModule() == field))
return;
ILExpression newObj = stsfld.Arguments[0];
if (!(newObj.Code == ILCode.Newobj && newObj.Arguments.Count == 2))
return;
if (newObj.Arguments[0].Code != ILCode.Ldnull)
return;
if (newObj.Arguments[1].Code != ILCode.Ldftn)
return;
MethodDefinition anonymousMethod = ((MethodReference)newObj.Arguments[1].Operand).ResolveWithinSameModule(); // method is defined in current assembly
if (!Ast.Transforms.DelegateConstruction.IsAnonymousMethod(context, anonymousMethod))
return;
ILNode followingNode = block.Body.ElementAtOrDefault(i + 1);
if (followingNode != null && followingNode.GetSelfAndChildrenRecursive<ILExpression>().Count(
e => e.Code == ILCode.Ldsfld && ((FieldReference)e.Operand).ResolveWithinSameModule() == field) == 1)
{
foreach (ILExpression parent in followingNode.GetSelfAndChildrenRecursive<ILExpression>()) {
for (int j = 0; j < parent.Arguments.Count; j++) {
if (parent.Arguments[j].Code == ILCode.Ldsfld && ((FieldReference)parent.Arguments[j].Operand).ResolveWithinSameModule() == field) {
parent.Arguments[j] = newObj;
block.Body.RemoveAt(i);
i -= new ILInlining(method).InlineInto(block.Body, i, aggressive: true);
return;
}
}
}
}
}
#endregion
#region MakeAssignmentExpression
bool MakeAssignmentExpression(List<ILNode> body, ILExpression expr, int pos)
{
// exprVar = ...
// stloc(v, exprVar)
// ->
// exprVar = stloc(v, ...))
ILVariable exprVar;
ILExpression initializer;
if (!(expr.Match(ILCode.Stloc, out exprVar, out initializer) && exprVar.IsGenerated))
return false;
ILExpression nextExpr = body.ElementAtOrDefault(pos + 1) as ILExpression;
ILVariable v;
ILExpression stLocArg;
if (nextExpr.Match(ILCode.Stloc, out v, out stLocArg) && stLocArg.MatchLdloc(exprVar)) {
ILExpression store2 = body.ElementAtOrDefault(pos + 2) as ILExpression;
if (StoreCanBeConvertedToAssignment(store2, exprVar)) {
// expr_44 = ...
// stloc(v1, expr_44)
// anystore(v2, expr_44)
// ->
// stloc(v1, anystore(v2, ...))
ILInlining inlining = new ILInlining(method);
if (inlining.numLdloc.GetOrDefault(exprVar) == 2 && inlining.numStloc.GetOrDefault(exprVar) == 1) {
body.RemoveAt(pos + 2); // remove store2
body.RemoveAt(pos); // remove expr = ...
nextExpr.Arguments[0] = store2;
store2.Arguments[store2.Arguments.Count - 1] = initializer;
inlining.InlineIfPossible(body, ref pos);
return true;
}
}
body.RemoveAt(pos + 1); // remove stloc
nextExpr.Arguments[0] = initializer;
((ILExpression)body[pos]).Arguments[0] = nextExpr;
return true;
} else {
// exprVar = ...
// stsfld(fld, exprVar)
// ->
// exprVar = stsfld(fld, ...))
FieldReference field;
if (nextExpr.Match(ILCode.Stsfld, out field, out stLocArg) && stLocArg.MatchLdloc(exprVar)) {
body.RemoveAt(pos + 1); // remove stfld
nextExpr.Arguments[0] = initializer;
((ILExpression)body[pos]).Arguments[0] = nextExpr;
return true;
}
}
return false;
}
bool StoreCanBeConvertedToAssignment(ILExpression store, ILVariable exprVar)
{
if (store != null && (store.Code == ILCode.Stloc || store.Code == ILCode.Stfld || store.Code == ILCode.Stsfld || IsArrayStore(store.Code))) {
return store.Arguments.Last().Code == ILCode.Ldloc && store.Arguments.Last().Operand == exprVar;
}
return false;
}
static bool IsArrayStore(ILCode code)
{
switch (code) {
case ILCode.Stelem_Any:
case ILCode.Stelem_Ref:
case ILCode.Stelem_I:
case ILCode.Stelem_I1:
case ILCode.Stelem_I2:
case ILCode.Stelem_I4:
case ILCode.Stelem_I8:
case ILCode.Stelem_R4:
case ILCode.Stelem_R8:
return true;
}
return false;
}
#endregion
#region MakeCompoundAssignments
bool MakeCompoundAssignments(List<ILNode> body, ILExpression expr, int pos)
{
bool modified = false;
modified |= MakeCompoundAssignmentForArray(expr);
modified |= MakeCompoundAssignmentForInstanceField(expr);
// Static fields and local variables are not handled here - those are expressions without side effects
// and get handled by ReplaceMethodCallsWithOperators
// (which does a reversible transform to the short operator form, as the introduction of checked/unchecked might have to revert to the long form).
foreach (ILExpression arg in expr.Arguments) {
modified |= MakeCompoundAssignments(null, arg, -1);
}
if (modified && body != null)
new ILInlining(method).InlineInto(body, pos, aggressive: false);
return modified;
}
bool MakeCompoundAssignmentForArray(ILExpression expr)
{
// stelem.any(..., ldloc(array), ldloc(pos), <OP>(ldelem.any(int32, ldloc(array), ldloc(pos)), <RIGHT>))
if (!IsArrayStore(expr.Code))
return false;
ILVariable arrayVar, posVar;
if (!(expr.Arguments[0].Match(ILCode.Ldloc, out arrayVar) && expr.Arguments[1].Match(ILCode.Ldloc, out posVar)))
return false;
// At least one of the variables must be generated; otherwise we just keep the expanded form.
if (!(arrayVar.IsGenerated || posVar.IsGenerated))
return false;
ILExpression op = expr.Arguments[2];
if (!CanBeRepresentedAsCompoundAssignment(op.Code))
return false;
ILExpression ldelem = op.Arguments[0];
if (!(ldelem.Code == ILCode.Ldelem_Any && ldelem.Arguments[0].MatchLdloc(arrayVar) && ldelem.Arguments[1].MatchLdloc(posVar)))
return false;
expr.Code = ILCode.CompoundAssignment;
expr.Operand = null;
expr.Arguments.RemoveRange(0, 2);
// result is "CompoundAssignment(<OP>(ldelem.any(...), <RIGHT>))"
return true;
}
bool MakeCompoundAssignmentForInstanceField(ILExpression expr)
{
// stfld(field, expr, <OP>(ldfld(field, expr), <RIGHT>))
FieldReference field;
ILExpression firstLoad, op;
ILVariable exprVar;
if (!(expr.Match(ILCode.Stfld, out field, out firstLoad, out op) && firstLoad.Match(ILCode.Ldloc, out exprVar) && exprVar.IsGenerated))
return false;
if (!CanBeRepresentedAsCompoundAssignment(op.Code))
return false;
ILExpression ldfld = op.Arguments[0];
if (!(ldfld.Code == ILCode.Ldfld && ldfld.Operand == field && ldfld.Arguments[0].MatchLdloc(exprVar)))
return false;
expr.Code = ILCode.CompoundAssignment;
expr.Operand = null;
expr.Arguments.RemoveAt(0);
// result is "CompoundAssignment(<OP>(ldfld(...), <RIGHT>))"
return true;
}
static bool CanBeRepresentedAsCompoundAssignment(ILCode code)
{
switch (code) {
case ILCode.Add:
case ILCode.Add_Ovf:
case ILCode.Add_Ovf_Un:
case ILCode.Sub:
case ILCode.Sub_Ovf:
case ILCode.Sub_Ovf_Un:
case ILCode.Mul:
case ILCode.Mul_Ovf:
case ILCode.Mul_Ovf_Un:
case ILCode.Div:
case ILCode.Div_Un:
case ILCode.Rem:
case ILCode.Rem_Un:
case ILCode.And:
case ILCode.Or:
case ILCode.Xor:
case ILCode.Shl:
case ILCode.Shr:
case ILCode.Shr_Un:
return true;
default:
return false;
}
}
#endregion
#region IntroduceFixedStatements
bool IntroduceFixedStatements(List<ILNode> body, int i)
{
ILExpression initValue;
ILVariable pinnedVar;
int initEndPos;
if (!MatchFixedInitializer(body, i, out pinnedVar, out initValue, out initEndPos))
return false;
ILFixedStatement fixedStmt = body.ElementAtOrDefault(initEndPos) as ILFixedStatement;
if (fixedStmt != null) {
ILExpression expr = fixedStmt.BodyBlock.Body.LastOrDefault() as ILExpression;
if (expr != null && expr.Code == ILCode.Stloc && expr.Operand == pinnedVar && IsNullOrZero(expr.Arguments[0])) {
// we found a second initializer for the existing fixed statement
fixedStmt.Initializers.Insert(0, initValue);
body.RemoveRange(i, initEndPos - i);
fixedStmt.BodyBlock.Body.RemoveAt(fixedStmt.BodyBlock.Body.Count - 1);
if (pinnedVar.Type.IsByReference)
pinnedVar.Type = new PointerType(((ByReferenceType)pinnedVar.Type).ElementType);
return true;
}
}
// find where pinnedVar is reset to 0:
int j;
for (j = initEndPos; j < body.Count; j++) {
ILVariable v2;
ILExpression storedVal;
// stloc(pinned_Var, conv.u(ldc.i4(0)))
if (body[j].Match(ILCode.Stloc, out v2, out storedVal) && v2 == pinnedVar) {
if (IsNullOrZero(storedVal)) {
break;
}
}
}
// Create fixed statement from i to j
fixedStmt = new ILFixedStatement();
fixedStmt.Initializers.Add(initValue);
fixedStmt.BodyBlock = new ILBlock(body.GetRange(initEndPos, j - initEndPos)); // from initEndPos to j-1 (inclusive)
body.RemoveRange(i + 1, Math.Min(j, body.Count - 1) - i); // from i+1 to j (inclusive)
body[i] = fixedStmt;
if (pinnedVar.Type.IsByReference)
pinnedVar.Type = new PointerType(((ByReferenceType)pinnedVar.Type).ElementType);
return true;
}
bool IsNullOrZero(ILExpression expr)
{
if (expr.Code == ILCode.Conv_U || expr.Code == ILCode.Conv_I)
expr = expr.Arguments[0];
return (expr.Code == ILCode.Ldc_I4 && (int)expr.Operand == 0) || expr.Code == ILCode.Ldnull;
}
bool MatchFixedInitializer(List<ILNode> body, int i, out ILVariable pinnedVar, out ILExpression initValue, out int nextPos)
{
if (body[i].Match(ILCode.Stloc, out pinnedVar, out initValue) && pinnedVar.IsPinned && !IsNullOrZero(initValue)) {
initValue = (ILExpression)body[i];
nextPos = i + 1;
HandleStringFixing(pinnedVar, body, ref nextPos, ref initValue);
return true;
}
ILCondition ifStmt = body[i] as ILCondition;
ILExpression arrayLoadingExpr;
if (ifStmt != null && MatchFixedArrayInitializerCondition(ifStmt.Condition, out arrayLoadingExpr)) {
ILVariable arrayVariable = (ILVariable)arrayLoadingExpr.Operand;
ILExpression trueValue;
if (ifStmt.TrueBlock != null && ifStmt.TrueBlock.Body.Count == 1
&& ifStmt.TrueBlock.Body[0].Match(ILCode.Stloc, out pinnedVar, out trueValue)
&& pinnedVar.IsPinned && IsNullOrZero(trueValue))
{
if (ifStmt.FalseBlock != null && ifStmt.FalseBlock.Body.Count == 1 && ifStmt.FalseBlock.Body[0] is ILFixedStatement) {
ILFixedStatement fixedStmt = (ILFixedStatement)ifStmt.FalseBlock.Body[0];
ILVariable stlocVar;
ILExpression falseValue;
if (fixedStmt.Initializers.Count == 1 && fixedStmt.BodyBlock.Body.Count == 0
&& fixedStmt.Initializers[0].Match(ILCode.Stloc, out stlocVar, out falseValue) && stlocVar == pinnedVar)
{
ILVariable loadedVariable;
if (falseValue.Code == ILCode.Ldelema
&& falseValue.Arguments[0].Match(ILCode.Ldloc, out loadedVariable) && loadedVariable == arrayVariable
&& IsNullOrZero(falseValue.Arguments[1]))
{
initValue = new ILExpression(ILCode.Stloc, pinnedVar, arrayLoadingExpr);
nextPos = i + 1;
return true;
}
}
}
}
}
initValue = null;
nextPos = -1;
return false;
}
bool MatchFixedArrayInitializerCondition(ILExpression condition, out ILExpression initValue)
{
ILExpression logicAnd;
ILVariable arrayVar1, arrayVar2;
if (condition.Match(ILCode.LogicNot, out logicAnd) && logicAnd.Code == ILCode.LogicAnd) {
initValue = UnpackDoubleNegation(logicAnd.Arguments[0]);
if (initValue.Match(ILCode.Ldloc, out arrayVar1)) {
ILExpression arrayLength = logicAnd.Arguments[1];
if (arrayLength.Code == ILCode.Conv_I4)
arrayLength = arrayLength.Arguments[0];
if (arrayLength.Code == ILCode.Ldlen && arrayLength.Arguments[0].Match(ILCode.Ldloc, out arrayVar2)) {
return arrayVar1 == arrayVar2;
}
}
}
initValue = null;
return false;
}
ILExpression UnpackDoubleNegation(ILExpression expr)
{
ILExpression negated;
if (expr.Match(ILCode.LogicNot, out negated) && negated.Match(ILCode.LogicNot, out negated))
return negated;
else
return expr;
}
bool HandleStringFixing(ILVariable pinnedVar, List<ILNode> body, ref int pos, ref ILExpression fixedStmtInitializer)
{
// fixed (stloc(pinnedVar, ldloc(text))) {
// var1 = var2 = conv.i(ldloc(pinnedVar))
// if (logicnot(logicnot(var1))) {
// var2 = add(var1, call(RuntimeHelpers::get_OffsetToStringData))
// }
// stloc(ptrVar, var2)
// ...
if (pos >= body.Count)
return false;
ILVariable var1, var2;
ILExpression varAssignment, ptrInitialization;
if (!(body[pos].Match(ILCode.Stloc, out var1, out varAssignment) && varAssignment.Match(ILCode.Stloc, out var2, out ptrInitialization)))
return false;
if (!(var1.IsGenerated && var2.IsGenerated))
return false;
if (ptrInitialization.Code == ILCode.Conv_I || ptrInitialization.Code == ILCode.Conv_U)
ptrInitialization = ptrInitialization.Arguments[0];
if (!ptrInitialization.MatchLdloc(pinnedVar))
return false;
ILCondition ifStmt = body[pos + 1] as ILCondition;
if (!(ifStmt != null && ifStmt.TrueBlock != null && ifStmt.TrueBlock.Body.Count == 1 && (ifStmt.FalseBlock == null || ifStmt.FalseBlock.Body.Count == 0)))
return false;
if (!UnpackDoubleNegation(ifStmt.Condition).MatchLdloc(var1))
return false;
ILVariable assignedVar;
ILExpression assignedExpr;
if (!(ifStmt.TrueBlock.Body[0].Match(ILCode.Stloc, out assignedVar, out assignedExpr) && assignedVar == var2 && assignedExpr.Code == ILCode.Add))
return false;
MethodReference calledMethod;
if (!(assignedExpr.Arguments[0].MatchLdloc(var1) && assignedExpr.Arguments[1].Match(ILCode.Call, out calledMethod)))
return false;
if (!(calledMethod.Name == "get_OffsetToStringData" && calledMethod.DeclaringType.FullName == "System.Runtime.CompilerServices.RuntimeHelpers"))
return false;
ILVariable pointerVar;
if (body[pos + 2].Match(ILCode.Stloc, out pointerVar, out assignedExpr) && assignedExpr.MatchLdloc(var2)) {
pos += 3;
fixedStmtInitializer.Operand = pointerVar;
return true;
}
return false;
}
#endregion
}
}