Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Fix analyzer treatment of flow captures of arrays #93420

Merged
merged 5 commits into from
Oct 18, 2023
Merged

Fix analyzer treatment of flow captures of arrays #93420

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
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
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 0 additions & 6 deletions src/tools/illink/src/ILLink.RoslynAnalyzer/DataFlow/LValueFlowCaptureProvider.cs
View file
Open in desktop
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
112 changes: 49 additions & 63 deletions src/tools/illink/src/ILLink.RoslynAnalyzer/DataFlow/LocalDataFlowVisitor.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
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
Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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.

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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

Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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 @@ -371,26 +337,31 @@ 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));
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));
Debug.Assert (!IsLValueFlowCapture (operation.Id),
$"{operation.Syntax.GetLocation ().GetLineSpan ()}");
Debug.Assert (operation.GetValueUsageInfo (OwningSymbol).HasFlag (ValueUsageInfo.Read),
$"{operation.Syntax.GetLocation ().GetLineSpan ()}");

return state.Get (new LocalKey (operation.Id));
}

// Similar to VisitLocalReference
public override TValue VisitFlowCaptureReference (IFlowCaptureReferenceOperation operation, LocalDataFlowState<TValue, TValueLattice> state)
{
if (operation.IsInitialization) {
// This capture reference is a temporary byref. This can happen for string
// interpolation handlers: https://github.com/dotnet/roslyn/issues/57484.
// Should really be treated as creating a new l-value flow capture,
// but this is likely irrelevant for dataflow analysis.

// LValueFlowCaptureProvider doesn't take into account IsInitialization = true,
// so it doesn't properly detect this as an l-value capture.
// Context: https://github.com/dotnet/roslyn/issues/60757
// Debug.Assert (IsLValueFlowCapture (operation.Id));
Debug.Assert (operation.GetValueUsageInfo (OwningSymbol).HasFlag (ValueUsageInfo.Write),
$"{operation.Syntax.GetLocation ().GetLineSpan ()}");
return TopValue;
}
return GetFlowCaptureValue (operation, state);
}

Expand All @@ -399,26 +370,41 @@ 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)) {
// 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;

// 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.
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
6 changes: 6 additions & 0 deletions src/tools/illink/test/ILLink.RoslynAnalyzer.Tests/DataFlowTests.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -161,6 +161,12 @@ public Task InlineArrayDataflow ()
return RunTest ();
}

[Fact]
public Task InterpolatedStringHandlerDataFlow ()
{
return RunTest ();
}

[Fact]
public Task MakeGenericDataFlow ()
{
Expand Down
118 changes: 118 additions & 0 deletions src/tools/illink/test/Mono.Linker.Tests.Cases/DataFlow/ArrayDataFlow.cs
View file
Open in desktop
Original file line number Diff line number Diff line change
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 ("IL2072", nameof (GetMethods), nameof (DataFlowTypeExtensions.RequiresAll),
ProducedBy = Tool.Analyzer)]
[ExpectedWarning ("IL2072", 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)
Copy link
Member Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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
Loading