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Fix analyzer treatment of flow captures of arrays #93420

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merged 5 commits into from
Oct 18, 2023
Merged

Fix analyzer treatment of flow captures of arrays #93420

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01dc9b7
Fix analyzer treatment of flow captures of arrays
sbomer Oct 12, 2023
daca428
Add back comment
sbomer Oct 12, 2023
3627e69
Fix expected warning
sbomer Oct 12, 2023
c5c4aeb
Add interpolated string handler test, fix asserts
sbomer Oct 17, 2023
f0726d2
Keep disabled assert as comment, add assert location
sbomer Oct 17, 2023
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6 changes: 0 additions & 6 deletions src/tools/illink/src/ILLink.RoslynAnalyzer/DataFlow/LValueFlowCaptureProvider.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -44,12 +44,6 @@ static bool IsLValueFlowCapture (IFlowCaptureReferenceOperation flowCaptureRefer
if (assignment?.Target == flowCaptureReference)
return true;

if (flowCaptureReference.Parent is IArrayElementReferenceOperation arrayAlementRef) {
assignment = arrayAlementRef.Parent as IAssignmentOperation;
if (assignment?.Target == arrayAlementRef)
return true;
}

assignment = null;
return flowCaptureReference.IsInLeftOfDeconstructionAssignment (out _);
}
Expand Down
99 changes: 34 additions & 65 deletions src/tools/illink/src/ILLink.RoslynAnalyzer/DataFlow/LocalDataFlowVisitor.cs
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Expand Up @@ -235,45 +235,11 @@ TValue ProcessSingleTargetAssignment (IOperation targetOperation, ISimpleAssignm
if (arrayElementRef.Indices.Length != 1)
break;

// Similarly to VisitSimpleAssignment, this needs to handle cases where the array reference
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This logic is no longer needed now that the array reference should never be an l-value capture. If the array reference is a flow capture, it should be an r-value capture, handled in the normal visitor logic.

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By this you mean, that the array (LHS) part of the ArrayReference should be an rvalue, right? Not the thing as a whole?

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Exactly - the (arr ?? arr2) temp should be an r-value, while (arr ?? arr2)[0] should be an l-value. At least that's how I think it should work after pondering this for a while, and is the behavior in the PR. ;)

// is a captured variable, even if the target of the assignment (the array element reference) is not.

TValue arrayRef;
TValue index;
TValue value;
if (arrayElementRef.ArrayReference is not IFlowCaptureReferenceOperation captureReference) {
arrayRef = Visit (arrayElementRef.ArrayReference, state);
index = Visit (arrayElementRef.Indices[0], state);
value = Visit (operation.Value, state);
HandleArrayElementWrite (arrayRef, index, value, operation, merge: merge);
return value;
}

index = Visit (arrayElementRef.Indices[0], state);
value = Visit (operation.Value, state);

var capturedReferences = state.Current.CapturedReferences.Get (captureReference.Id);
if (!capturedReferences.HasMultipleValues) {
// Single captured reference. Treat this as an overwriting assignment,
// unless the caller already told us to merge values because this is an
// assignment to one of multiple captured array element references.
var enumerator = capturedReferences.GetEnumerator ();
enumerator.MoveNext ();
var capture = enumerator.Current;
arrayRef = Visit (capture.Reference, state);
HandleArrayElementWrite (arrayRef, index, value, operation, merge: merge);
return value;
}

// The capture id may have captured multiple references, as in:
// (b ? arr1 : arr2)[0] = value;
// We treat this as possible write to each of the captured references,
// which requires merging with the previous values of each.

foreach (var capture in state.Current.CapturedReferences.Get (captureReference.Id)) {
arrayRef = Visit (capture.Reference, state);
HandleArrayElementWrite (arrayRef, index, value, operation, merge: true);
}
TValue arrayRef = Visit (arrayElementRef.ArrayReference, state);
TValue index = Visit (arrayElementRef.Indices[0], state);
TValue value = Visit (operation.Value, state);
HandleArrayElementWrite (arrayRef, index, value, operation, merge: merge);
return value;
}
case IInlineArrayAccessOperation inlineArrayAccess: {
Expand Down Expand Up @@ -371,19 +337,10 @@ public override TValue VisitSimpleAssignment (ISimpleAssignmentOperation operati

TValue GetFlowCaptureValue (IFlowCaptureReferenceOperation operation, LocalDataFlowState<TValue, TValueLattice> state)
{
if (!operation.GetValueUsageInfo (OwningSymbol).HasFlag (ValueUsageInfo.Read)) {
// There are known cases where this assert doesn't hold, because LValueFlowCaptureProvider
// produces the wrong result in some cases for flow captures with IsInitialization = true.
// https://github.com/dotnet/linker/issues/2749
// Debug.Assert (IsLValueFlowCapture (operation.Id));
Debug.Assert (!IsLValueFlowCapture (operation.Id));
Debug.Assert (operation.GetValueUsageInfo (OwningSymbol).HasFlag (ValueUsageInfo.Read));
if (!operation.GetValueUsageInfo (OwningSymbol).HasFlag (ValueUsageInfo.Read))
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return TopValue;
}

// This assert is incorrect for cases like (b ? arr1 : arr2)[0] = v;
// Here the ValueUsageInfo shows that the value usage is for reading (this is probably wrong!)
// but the value is actually an LValueFlowCapture.
// Let's just disable the assert for now.
// Debug.Assert (IsRValueFlowCapture (operation.Id));

return state.Get (new LocalKey (operation.Id));
}
Expand All @@ -399,26 +356,38 @@ public override TValue VisitFlowCaptureReference (IFlowCaptureReferenceOperation
// is like a local reference.
public override TValue VisitFlowCapture (IFlowCaptureOperation operation, LocalDataFlowState<TValue, TValueLattice> state)
{
// If the captured value is a property reference, we can't easily tell inside of
// VisitPropertyReference whether it is accessed for reads or writes.
// https://github.com/dotnet/roslyn/issues/25057
// Avoid visiting the captured value unless it is an RValue.
if (IsLValueFlowCapture (operation.Id)) {
// Note: technically we should save some information about the value for LValue flow captures
// (for example, the object instance of a property reference) and avoid re-computing it when
// assigning to the FlowCaptureReference.
// Should never see an l-value flow capture of another flow capture.
Debug.Assert (operation.Value is not IFlowCaptureReferenceOperation);
if (operation.Value is IFlowCaptureReferenceOperation)
return TopValue;

var capturedRef = new CapturedReferenceValue (operation.Value);
var currentState = state.Current;
currentState.CapturedReferences.Set (operation.Id, new CapturedReferenceValue (operation.Value));
currentState.CapturedReferences.Set (operation.Id, capturedRef);
state.Current = currentState;
}
return TopValue;
} else {
TValue capturedValue;
if (operation.Value is IFlowCaptureReferenceOperation captureRef) {
if (IsLValueFlowCapture (captureRef.Id)) {
// If an r-value captures an l-value, we must dereference the l-value
// and copy out the value to capture.
capturedValue = TopValue;
foreach (var capturedReference in state.Current.CapturedReferences.Get (captureRef.Id)) {
var value = Visit (capturedReference.Reference, state);
capturedValue = LocalStateLattice.Lattice.ValueLattice.Meet (capturedValue, value);
}
} else {
capturedValue = state.Get (new LocalKey (captureRef.Id));
}
} else {
capturedValue = Visit (operation.Value, state);
}

if (IsRValueFlowCapture (operation.Id)) {
TValue value = Visit (operation.Value, state);
state.Set (new LocalKey (operation.Id), value);
return value;
state.Set (new LocalKey (operation.Id), capturedValue);
return capturedValue;
}

return TopValue;
}

public override TValue VisitExpressionStatement (IExpressionStatementOperation operation, LocalDataFlowState<TValue, TValueLattice> state)
Expand Down
118 changes: 118 additions & 0 deletions src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/ArrayDataFlow.cs
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Expand Up @@ -3,6 +3,8 @@

using System;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using Mono.Linker.Tests.Cases.Expectations.Assertions;
using Mono.Linker.Tests.Cases.Expectations.Helpers;

Expand Down Expand Up @@ -30,6 +32,7 @@ public static void Main ()
TestArraySetElementAndInitializerMultipleElementsMix<TestType> (typeof (TestType));

TestGetElementAtUnknownIndex ();
TestGetMergedArrayElement ();
TestMergedArrayElementWithUnknownIndex (0);

// Array reset - certain operations on array are not tracked fully (or impossible due to unknown inputs)
Expand All @@ -47,6 +50,8 @@ public static void Main ()

WriteCapturedArrayElement.Test ();

WriteElementOfCapturedArray.Test ();

ConstantFieldValuesAsIndex.Test ();

HoistedArrayMutation.Test ();
Expand Down Expand Up @@ -205,6 +210,23 @@ static void TestGetElementAtUnknownIndex (int i = 0)
arr[i].RequiresPublicFields ();
}

// https://github.com/dotnet/runtime/issues/93416 tracks the discrepancy between
// the analyzer and ILLink/ILCompiler.
[ExpectedWarning ("IL2062", nameof (DataFlowTypeExtensions.RequiresAll),
ProducedBy = Tool.Trimmer | Tool.NativeAot)]
[ExpectedWarning ("IL2087", nameof (GetMethods), nameof (DataFlowTypeExtensions.RequiresAll),
ProducedBy = Tool.Analyzer)]
[ExpectedWarning ("IL2087", nameof (GetFields), nameof (DataFlowTypeExtensions.RequiresAll),
ProducedBy = Tool.Analyzer)]
static void TestGetMergedArrayElement (bool b = true)
{
Type[] arr = new Type[] { GetMethods () };
Type[] arr2 = new Type[] { GetFields () };
if (b)
arr = arr2;
arr[0].RequiresAll ();
}

// Trimmer code doesnt handle locals from different branches separetely, therefore merges incorrectly GetMethods with Unknown producing both warnings
[ExpectedWarning ("IL2072", nameof (ArrayDataFlow.GetMethods), ProducedBy = Tool.Trimmer | Tool.NativeAot)]
[ExpectedWarning ("IL2062", nameof (DataFlowTypeExtensions.RequiresAll))]
Expand Down Expand Up @@ -614,6 +636,102 @@ public static void Test ()
}
}

class WriteElementOfCapturedArray
{
[Kept]
[ExpectedWarning ("IL2072", nameof (GetUnknownType), nameof (DataFlowTypeExtensions.RequiresAll))]
[ExpectedWarning ("IL2072", nameof (GetTypeWithPublicConstructors), nameof (DataFlowTypeExtensions.RequiresAll))]
// Analysis hole: https://github.com/dotnet/runtime/issues/90335
// The array element assignment assigns to a temp array created as a copy of
// arr1 or arr2, and writes to it aren't reflected back in arr1/arr2.
static void TestArrayElementAssignment (bool b = true)
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Test moved from ByRefDataflow. Note this introduces a behavior change: analyzer no longer produces warnings for the GetWithPublicMethods value, bringing it closer to the ILLink/ILCompiler behavior. Once we fix the tracking of reference types, it should fix all three.

{
var arr1 = new Type[] { GetUnknownType () };
var arr2 = new Type[] { GetTypeWithPublicConstructors () };
(b ? arr1 : arr2)[0] = GetWithPublicMethods ();
arr1[0].RequiresAll ();
arr2[0].RequiresAll ();
}

[Kept]
[KeptAttributeAttribute (typeof (InlineArrayAttribute))]
[InlineArray (8)]
public struct InlineTypeArray
{
[Kept]
public Type t;
}

[Kept]
[ExpectedWarning ("IL2062", nameof (DataFlowTypeExtensions.RequiresAll))]
[ExpectedWarning ("IL2062", nameof (DataFlowTypeExtensions.RequiresAll))]
static void TestInlineArrayElementReferenceAssignment (bool b = true)
{
var arr1 = new InlineTypeArray ();
arr1[0] = GetUnknownType ();
var arr2 = new InlineTypeArray ();
arr2[0] = GetTypeWithPublicConstructors ();
(b ? ref arr1[0] : ref arr2[0]) = GetTypeWithPublicConstructors ();
arr1[0].RequiresAll ();
arr2[0].RequiresAll ();
}

// Inline array references are not allowed in conditionals, unlike array references.
// static void TestInlineArrayElementAssignment (bool b = true)
// {
// var arr1 = new InlineTypeArray ();
// arr1[0] = GetUnknownType ();
// var arr2 = new InlineTypeArray ();
// arr2[0] = GetTypeWithPublicConstructors ();
// (b ? arr1 : arr2)[0] = GetWithPublicMethods ();
// arr1[0].RequiresAll ();
// arr2[0].RequiresAll ();
// }

[ExpectedWarning ("IL2087", nameof (T), nameof (DataFlowTypeExtensions.RequiresAll))]
[ExpectedWarning ("IL2087", nameof (U), nameof (DataFlowTypeExtensions.RequiresPublicFields))]
// Missing warnings for 'V' possibly assigned to arr or arr2 because write to temp
// array isn't reflected back in the local variables. https://github.com/dotnet/linker/issues/2158
static void TestNullCoalesce<T, U, V> (bool b = false)
{
Type[]? arr = new Type[1] { typeof (T) };
Type[] arr2 = new Type[1] { typeof (U) };

(arr ?? arr2)[0] = typeof (V);
arr[0].RequiresAll ();
arr2[0].RequiresPublicFields ();
}

[ExpectedWarning ("IL2087", nameof (T), nameof (DataFlowTypeExtensions.RequiresAll), ProducedBy = Tool.Analyzer)]
[ExpectedWarning ("IL2087", nameof (U), nameof (DataFlowTypeExtensions.RequiresPublicFields))]
// Missing warnings for 'V' possibly assigned to arr or arr2 because write to temp
// array isn't reflected back in the local variables. https://github.com/dotnet/linker/issues/2158
// This also causes an extra analyzer warning for 'U' in 'arr', because the analyzer models the
// possible assignment of arr2 to arr, without overwriting index '0'. And it produces a warning
// for each possible value, unlike ILLink/ILCompiler, which produce an unknown value for a merged
// array value: https://github.com/dotnet/runtime/issues/93416
[ExpectedWarning ("IL2087", nameof (U), nameof (DataFlowTypeExtensions.RequiresAll), ProducedBy = Tool.Analyzer)]
[ExpectedWarning ("IL2062", nameof (DataFlowTypeExtensions.RequiresAll), ProducedBy = Tool.Trimmer | Tool.NativeAot)]
static void TestNullCoalescingAssignment<T, U, V> (bool b = true)
{
Type[]? arr = new Type[1] { typeof (T) };
Type[] arr2 = new Type[1] { typeof (U) };

(arr ??= arr2)[0] = typeof (V);
arr[0].RequiresAll ();
arr2[0].RequiresPublicFields ();
}

public static void Test ()
{
TestArrayElementAssignment ();
TestInlineArrayElementReferenceAssignment ();
// TestInlineArrayElementAssignment ();
TestNullCoalesce<int, int, int> ();
TestNullCoalescingAssignment<int, int, int> ();
}
}

class ConstantFieldValuesAsIndex
{
private const sbyte ConstSByte = 1;
Expand Down
55 changes: 0 additions & 55 deletions src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/ByRefDataflow.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,8 +4,6 @@
using System;
using System.Diagnostics.CodeAnalysis;
using System.Reflection;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using Mono.Linker.Tests.Cases.Expectations.Assertions;
using Mono.Linker.Tests.Cases.Expectations.Metadata;
using Mono.Linker.Tests.Cases.Expectations.Helpers;
Expand Down Expand Up @@ -261,56 +259,6 @@ static void TestArrayElementReferenceAssignment (bool b = true)
arr2[0].RequiresAll ();
}

[Kept]
[ExpectedWarning ("IL2072", nameof (GetUnknownType), nameof (DataFlowTypeExtensions.RequiresAll))]
[ExpectedWarning ("IL2072", nameof (GetTypeWithPublicConstructors), nameof (DataFlowTypeExtensions.RequiresAll))]
// ILLink/ILCompiler analysis hole: https://github.com/dotnet/runtime/issues/90335
[ExpectedWarning ("IL2072", nameof (GetTypeWithPublicFields), nameof (DataFlowTypeExtensions.RequiresAll), ProducedBy = Tool.Analyzer)]
[ExpectedWarning ("IL2072", nameof (GetTypeWithPublicFields), nameof (DataFlowTypeExtensions.RequiresAll), ProducedBy = Tool.Analyzer)]
static void TestArrayElementAssignment (bool b = true)
{
var arr1 = new Type[] { GetUnknownType () };
var arr2 = new Type[] { GetTypeWithPublicConstructors () };
(b ? arr1 : arr2)[0] = GetTypeWithPublicFields ();
arr1[0].RequiresAll ();
arr2[0].RequiresAll ();
}

[Kept]
[KeptAttributeAttribute (typeof (InlineArrayAttribute))]
[InlineArray (8)]
public struct InlineTypeArray
{
[Kept]
public Type t;
}

[Kept]
[ExpectedWarning ("IL2062", nameof (DataFlowTypeExtensions.RequiresAll))]
[ExpectedWarning ("IL2062", nameof (DataFlowTypeExtensions.RequiresAll))]
static void TestInlineArrayElementReferenceAssignment (bool b = true)
{
var arr1 = new InlineTypeArray ();
arr1[0] = GetUnknownType ();
var arr2 = new InlineTypeArray ();
arr2[0] = GetTypeWithPublicConstructors ();
(b ? ref arr1[0] : ref arr2[0]) = GetTypeWithPublicFields ();
arr1[0].RequiresAll ();
arr2[0].RequiresAll ();
}

// Inline array references are not allowed in conditionals, unlike array references.
// static void TestInlineArrayElementAssignment (bool b = true)
// {
// var arr1 = new InlineTypeArray ();
// arr1[0] = GetUnknownType ();
// var arr2 = new InlineTypeArray ();
// arr2[0] = GetTypeWithPublicConstructors ();
// (b ? arr1 : arr2)[0] = GetTypeWithPublicFields ();
// arr1[0].RequiresAll ();
// arr2[0].RequiresAll ();
// }

[Kept]
[ExpectedWarning ("IL2074", nameof (_publicMethodsField), nameof (GetUnknownType))]
[ExpectedWarning ("IL2074", nameof (_publicPropertiesField), nameof (GetUnknownType))]
Expand Down Expand Up @@ -358,9 +306,6 @@ public static void Test ()
TestParameterAssignment ();
TestLocalAssignment ();
TestArrayElementReferenceAssignment ();
TestArrayElementAssignment ();
TestInlineArrayElementReferenceAssignment ();
// TestInlineArrayElementAssignment ();
TestNullCoalescingAssignment ();
TestNullCoalescingAssignmentComplex ();
TestDataFlowOnRightHandOfAssignment ();
Expand Down
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