[wasm] Report untracked GC slots for aborted Wasm R2R frames

docs/design/datacontracts/GCInfo.md

@@ -220,7 +220,7 @@ The fat header is used for methods that cannot be encoded using the compact slim
 | ReversePInvokeFrameSlot | `REVERSE_PINVOKE_FRAME_ENCBASE` | Normalized reverse P/Invoke frame slot | If GC_INFO_REVERSE_PINVOKE_FRAME |
 | SizeOfStackOutgoingAndScratchArea | `SIZE_OF_STACK_AREA_ENCBASE` | Size of stack parameter area | Platform dependent |
 | NumSafePoints | `NUM_SAFE_POINTS_ENCBASE` | Number of safe points/callsites | #ifdef PARTIALLY_INTERRUPTIBLE_GC_SUPPORTED |
-| NumInterruptibleRanges | `NUM_INTERRUPTIBLE_RANGES_ENCBASE` | Number of interruptible ranges | |
+| NumInterruptibleRanges | `NUM_INTERRUPTIBLE_RANGES_ENCBASE` | Number of interruptible ranges | If `HAS_INTERRUPTIBLE_RANGES` (omitted for Wasm R2R) |
 
 ##### Header Flags
 
@@ -517,7 +517,10 @@ if HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA:  // platform-dependent
     fixedStackParameterScratchArea = DenormalizeSizeOfStackArea(DecodeVarLengthUnsigned(...))
 
 numSafePoints = DecodeVarLengthUnsigned(NUM_SAFE_POINTS_ENCBASE)
-numInterruptibleRanges = DecodeVarLengthUnsigned(NUM_INTERRUPTIBLE_RANGES_ENCBASE)
+if HAS_INTERRUPTIBLE_RANGES:  // false for Wasm R2R, which never has interruptible ranges
+    numInterruptibleRanges = DecodeVarLengthUnsigned(NUM_INTERRUPTIBLE_RANGES_ENCBASE)
+else:
+    numInterruptibleRanges = 0
 ```
 
 #### Body Decoding
@@ -647,6 +650,8 @@ For each chunk, the encoding stores:
 
 To determine liveness at the target offset: start from the chunk's final state, then apply any transitions that occur *after* the target offset (toggling the state backwards). A slot is live if its final state (after toggle adjustment) is 1.
 
+For encodings without interruptible ranges (`HAS_INTERRUPTIBLE_RANGES` is false, as for Wasm R2R), this step is replaced by reporting only untracked slots, including for `ExecutionAborted` frames. An aborted funclet shares those slots with parent frames that are skipped.
+
 **Step 4 — Report untracked slots**: Untracked slots are always live (they represent stack locations the JIT doesn't track at each safe point). They are reported unconditionally unless `ParentOfFuncletStackFrame` or `NoReportUntracked` flags are set. Untracked slots are reported with `reportScratchSlots=true` since the JIT may produce untracked scratch register slots for interior pointers.
 
 **Slot filtering**: Before reporting any slot, the algorithm checks:

src/coreclr/gcinfo/gcinfoencoder.cpp

@@ -612,6 +612,8 @@ template <typename GcInfoEncoding> void TGcInfoEncoder<GcInfoEncoding>::WriteSlo
 
 template <typename GcInfoEncoding> void TGcInfoEncoder<GcInfoEncoding>::DefineInterruptibleRange( UINT32 startInstructionOffset, UINT32 length )
 {
+    _ASSERTE(GcInfoEncoding::HAS_INTERRUPTIBLE_RANGES);
+
     UINT32 stopInstructionOffset = startInstructionOffset + length;
 
     UINT32 normStartOffset = GcInfoEncoding::NORMALIZE_CODE_OFFSET(startInstructionOffset);
@@ -1108,7 +1110,7 @@ template <typename GcInfoEncoding> void TGcInfoEncoder<GcInfoEncoding>::Build()
     m_NumCallSites = numCallSites;
 #endif // PARTIALLY_INTERRUPTIBLE_GC_SUPPORTED
 
-    if (slimHeader)
+    if (slimHeader || !GcInfoEncoding::HAS_INTERRUPTIBLE_RANGES)
     {
         _ASSERTE(numInterruptibleRanges == 0);
     }

src/coreclr/inc/gcinfoencoder.h

@@ -43,7 +43,7 @@
     - ReversePInvokeFrameSlot (if any)
     - SizeOfStackOutgoingAndScratchArea (#ifdef FIXED_STACK_PARAMETER_SCRATCH_AREA)
     - NumCallSites (#ifdef PARTIALLY_INTERRUPTIBLE_GC_SUPPORTED)
-    - NumInterruptibleRanges
+    - NumInterruptibleRanges (fat header only; omitted if !HAS_INTERRUPTIBLE_RANGES)
 
  2. Call sites offsets (#ifdef PARTIALLY_INTERRUPTIBLE_GC_SUPPORTED)
  3. Fully-interruptible ranges

src/coreclr/inc/gcinfotypes.h

@@ -618,6 +618,7 @@ struct AMD64GcInfoEncoding {
     static const int LIVESTATE_RLE_RUN_ENCBASE = 2;
     static const int LIVESTATE_RLE_SKIP_ENCBASE = 4;
     static const bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA = true;
+    static const bool HAS_INTERRUPTIBLE_RANGES = true;
 };
 
 #elif defined(TARGET_ARM)
@@ -676,6 +677,7 @@ struct ARM32GcInfoEncoding {
     static const int LIVESTATE_RLE_RUN_ENCBASE = 2;
     static const int LIVESTATE_RLE_SKIP_ENCBASE = 4;
     static const bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA = true;
+    static const bool HAS_INTERRUPTIBLE_RANGES = true;
 };
 
 #elif defined(TARGET_ARM64)
@@ -737,6 +739,7 @@ struct ARM64GcInfoEncoding {
     static const int LIVESTATE_RLE_RUN_ENCBASE = 2;
     static const int LIVESTATE_RLE_SKIP_ENCBASE = 4;
     static const bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA = true;
+    static const bool HAS_INTERRUPTIBLE_RANGES = true;
 };
 
 #elif defined(TARGET_LOONGARCH64)
@@ -796,6 +799,7 @@ struct LoongArch64GcInfoEncoding {
     static const int LIVESTATE_RLE_RUN_ENCBASE = 2;
     static const int LIVESTATE_RLE_SKIP_ENCBASE = 4;
     static const bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA = true;
+    static const bool HAS_INTERRUPTIBLE_RANGES = true;
 };
 
 #elif defined(TARGET_RISCV64)
@@ -856,6 +860,7 @@ struct RISCV64GcInfoEncoding {
     static const int LIVESTATE_RLE_RUN_ENCBASE = 2;
     static const int LIVESTATE_RLE_SKIP_ENCBASE = 4;
     static const bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA = true;
+    static const bool HAS_INTERRUPTIBLE_RANGES = true;
 };
 
 #elif defined(TARGET_X86)
@@ -911,6 +916,7 @@ struct X86GcInfoEncoding {
     static const int LIVESTATE_RLE_RUN_ENCBASE = 2;
     static const int LIVESTATE_RLE_SKIP_ENCBASE = 4;
     static const bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA = true;
+    static const bool HAS_INTERRUPTIBLE_RANGES = true;
 };
 
 #elif defined(TARGET_WASM) && !defined(TARGET_64BIT)
@@ -968,6 +974,7 @@ struct Wasm32GcInfoEncoding {
     static const int LIVESTATE_RLE_RUN_ENCBASE = 2;
     static const int LIVESTATE_RLE_SKIP_ENCBASE = 4;
     static const bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA = false;
+    static const bool HAS_INTERRUPTIBLE_RANGES = false;
 };
 
 #else // No target defined
@@ -1031,6 +1038,7 @@ struct InterpreterGcInfoEncoding {
     static const int LIVESTATE_RLE_RUN_ENCBASE = 2;
     static const int LIVESTATE_RLE_SKIP_ENCBASE = 4;
     static const bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA = false;
+    static const bool HAS_INTERRUPTIBLE_RANGES = true;
 };
 
 #endif // FEATURE_INTERPRETER

src/coreclr/tools/aot/ILCompiler.Reflection.ReadyToRun/Amd64/GcInfo.cs

@@ -174,7 +174,7 @@ public GcInfo(NativeReader imageReader, int offset, Machine machine, int version
             // PARTIALLY_INTERRUPTIBLE_GC_SUPPORTED (this macro is always defined in _gcInfoTypes.h)
             NumSafePoints = imageReader.DecodeVarLengthUnsigned(_gcInfoTypes.NUM_SAFE_POINTS_ENCBASE, ref bitOffset);
 
-            if (!_slimHeader)
+            if (!_slimHeader && _gcInfoTypes.HAS_INTERRUPTIBLE_RANGES)
             {
                 NumInterruptibleRanges = imageReader.DecodeVarLengthUnsigned(_gcInfoTypes.NUM_INTERRUPTIBLE_RANGES_ENCBASE, ref bitOffset);
             }

src/coreclr/tools/aot/ILCompiler.Reflection.ReadyToRun/GCInfoTypes.cs

@@ -120,6 +120,7 @@ public class GcInfoTypes
         internal int LIVESTATE_RLE_SKIP_ENCBASE { get; } = 4;
         internal int NUM_NORM_CODE_OFFSETS_PER_CHUNK_LOG2 { get; } = 6;
         internal bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA { get; } = true;
+        internal bool HAS_INTERRUPTIBLE_RANGES { get; } = true;
 
         internal GcInfoTypes(Machine machine, bool denormalizeCodeOffsets)
         {
@@ -180,6 +181,7 @@ internal GcInfoTypes(Machine machine, bool denormalizeCodeOffsets)
                     LIVESTATE_RLE_RUN_ENCBASE = 2;
                     LIVESTATE_RLE_SKIP_ENCBASE = 4;
                     HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA = false;
+                    HAS_INTERRUPTIBLE_RANGES = false;
                     break;
 
                 case Machine.I386:

src/coreclr/vm/gcinfodecoder.cpp

@@ -374,7 +374,7 @@ TGcInfoDecoder<GcInfoEncoding>::TGcInfoDecoder(
     m_SafePointIndex = m_NumSafePoints;
 #endif
 
-    if (slimHeader)
+    if (slimHeader || !GcInfoEncoding::HAS_INTERRUPTIBLE_RANGES)
     {
         m_NumInterruptibleRanges = 0;
     }
@@ -736,6 +736,7 @@ template <typename GcInfoEncoding> bool TGcInfoDecoder<GcInfoEncoding>::Enumerat
 {
 
     unsigned executionAborted = (inputFlags & ExecutionAborted);
+    bool reportUntrackedOnly = false;
 
     // In order to make ARM more x86-like we only ever report the leaf frame
     // of any given function. We accomplish this by having the stackwalker
@@ -777,6 +778,12 @@ template <typename GcInfoEncoding> bool TGcInfoDecoder<GcInfoEncoding>::Enumerat
             m_Reader.DecodeVarLengthUnsigned( GcInfoEncoding::INTERRUPTIBLE_RANGE_DELTA2_ENCBASE );
         }
     }
+    else if constexpr (!GcInfoEncoding::HAS_INTERRUPTIBLE_RANGES)
+    {
+        // Outside of safe points only untracked slots can be reported. Report them for aborted
+        // frames too: an aborted funclet shares them with parent frames that are skipped.
+        reportUntrackedOnly = true;
+    }
     else
     {
         //
@@ -829,6 +836,9 @@ template <typename GcInfoEncoding> bool TGcInfoDecoder<GcInfoEncoding>::Enumerat
 
     slotDecoder.DecodeSlotTable(m_Reader);
 
+    if (reportUntrackedOnly)
+        goto ReportUntracked;
+
     {
         UINT32 numSlots = slotDecoder.GetNumTracked();
 

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/GCInfoDecoder.cs

@@ -493,7 +493,9 @@ private IEnumerable<DecodePoints> DecodeFatHeader()
             _numSafePoints = _reader.DecodeVarLengthUnsigned(TTraits.NUM_SAFE_POINTS_ENCBASE, ref _bitOffset);
         }
 
-        _numInterruptibleRanges = _reader.DecodeVarLengthUnsigned(TTraits.NUM_INTERRUPTIBLE_RANGES_ENCBASE, ref _bitOffset);
+        _numInterruptibleRanges = TTraits.HAS_INTERRUPTIBLE_RANGES
+            ? _reader.DecodeVarLengthUnsigned(TTraits.NUM_INTERRUPTIBLE_RANGES_ENCBASE, ref _bitOffset)
+            : 0;
     }
 
     private void EnsureDecodedTo(DecodePoints point)
@@ -976,6 +978,12 @@ private bool EnumerateLiveSlots(
             {
                 // We have a safe point match — skip interruptible range computation
             }
+            else if (!TTraits.HAS_INTERRUPTIBLE_RANGES)
+            {
+                // Outside of safe points only untracked slots can be reported. Report them for aborted
+                // frames too: an aborted funclet shares them with parent frames that are skipped.
+                return ReportUntrackedAndSucceed();
+            }
             else
             {
                 // Compute pseudoBreakOffset from interruptible ranges

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/PlatformTraits/IGCInfoTraits.cs

@@ -50,6 +50,9 @@ internal interface IGCInfoTraits
 
     static abstract bool HAS_FIXED_STACK_PARAMETER_SCRATCH_AREA { get; }
 
+    // False for encodings whose code is never interruptible (Wasm R2R).
+    static virtual bool HAS_INTERRUPTIBLE_RANGES => true;
+
     /// <summary>
     /// Returns true if the given register is a scratch (volatile) register.
     /// Scratch register slots should only be reported for the active (leaf) stack frame.