remove GCCover contract and move API to CodeVersions

Author: Max Charlamb

docs/design/datacontracts/CodeVersions.md

@@ -40,6 +40,9 @@ public virtual bool CodeVersionManagerSupportsMethod(TargetPointer methodDesc);
 
 // Return the instruction pointer corresponding to the start of the given native code version
 public virtual TargetCodePointer GetNativeCode(NativeCodeVersionHandle codeVersionHandle);
+
+// Gets the GCStressCodeCopy pointer if available, otherwise returns TargetPointer.Null
+public virtual TargetPointer GetGCStressCodeCopy(NativeCodeVersionHandle codeVersionHandle);
 ```
 ### Extension Methods
 ```csharp
@@ -61,13 +64,15 @@ Data descriptors used:
 | NativeCodeVersionNode | NativeCode | indicates an explicit native code version node |
 | NativeCodeVersionNode | Flags | `NativeCodeVersionNodeFlags` flags, see below |
 | NativeCodeVersionNode | VersionId | Version ID corresponding to the parent IL code version |
+| NativeCodeVersionNode | GCCoverageInfo | GCStress debug info, if supported |
 | ILCodeVersioningState | FirstVersionNode | pointer to the first `ILCodeVersionNode` |
 | ILCodeVersioningState | ActiveVersionKind | an `ILCodeVersionKind` value indicating which fields of the active version are value |
 | ILCodeVersioningState | ActiveVersionNode | if the active version is explicit, the NativeCodeVersionNode for the active version |
 | ILCodeVersioningState | ActiveVersionModule | if the active version is synthetic or unknown, the pointer to the Module that defines the method |
 | ILCodeVersioningState | ActiveVersionMethodDef | if the active version is synthetic or unknown, the MethodDef token for the method |
 | ILCodeVersionNode | VersionId | Version ID of the node |
 | ILCodeVersionNode | Next | Pointer to the next `ILCodeVersionNode`|
+| GCCoverageInfo | SavedCode | Pointer to the GCCover saved code copy |
 
 The flag indicates that the default version of the code for a method desc is active:
 ```csharp
@@ -249,3 +254,11 @@ bool ICodeVersions.CodeVersionManagerSupportsMethod(TargetPointer methodDescAddr
     return true;
 }
 ```
+
+### Finding GCStress Code Copy
+```csharp
+public virtual TargetPointer GetGCStressCodeCopy(NativeCodeVersionHandle codeVersionHandle);
+```
+
+1. If `codeVersionHandle` is synthetic, use the `IRuntimeTypeSystem` to find the GCStressCodeCopy.
+2. If `codeVersionHandle` is explicit, read the `NativeCodeVersionNode` for the `GCCoverageInfo` pointer. This value is nullable as it only exists in some builds. If the value doesn't exist or is a nullptr, return `TargetPointer.Null`. Otherwise return the `SavedCode` pointer from the `GCCoverageInfo` struct.

docs/design/datacontracts/RuntimeTypeSystem.md

@@ -159,8 +159,8 @@ partial interface IRuntimeTypeSystem : IContract
     // Get an instruction pointer that can be called to cause the MethodDesc to be executed
     public virtual TargetCodePointer GetNativeCode(MethodDescHandle methodDesc);
 
-    // Gets the GCCoverageInfo pointer if available, otherwise returns TargetPointer.Null
-    public virtual TargetPointer GetGCCoverageInfo(MethodDescHandle methodDesc);
+    // Gets the GCStressCodeCopy pointer if available, otherwise returns TargetPointer.Null
+    public virtual TargetPointer GetGCStressCodeCopy(MethodDescHandle methodDesc);
 }
 ```
 
@@ -640,6 +640,7 @@ We depend on the following data descriptors:
 | `MethodDesc` | `Slot` | The method's slot |
 | `MethodDesc` | `Flags` | The method's flags |
 | `MethodDesc` | `Flags3AndTokenRemainder` | More flags for the method, and the low bits of the method's token's RID |
+| `MethodDesc` | `GCCoverageInfo` | The method's GCCover debug info, if supported |
 | `MethodDescCodeData` | `VersioningState` | The IL versioning state associated with a method descriptor
 | `MethodDescChunk` | `MethodTable` | The method table set of methods belongs to |
 | `MethodDescChunk` | `Next` | The next chunk of methods |
@@ -656,6 +657,7 @@ We depend on the following data descriptors:
 | `StoredSigMethodDesc` | `cSig` | Count of bytes in the metadata signature |
 | `StoredSigMethodDesc` | `ExtendedFlags` | Flags field for the `StoredSigMethodDesc` |
 | `DynamicMethodDesc` | `MethodName` | Pointer to Null-terminated UTF8 string describing the Method desc |
+| `GCCoverageInfo` | `SavedCode` | Pointer to the GCCover saved code copy |
 
 
 The contract depends on the following other contracts

src/coreclr/debug/runtimeinfo/contracts.jsonc

@@ -14,7 +14,6 @@
   "EcmaMetadata" : 1,
   "Exception": 1,
   "ExecutionManager": 2,
-  "GCCover": 1,
   "Loader": 1,
   "Object": 1,
   "PlatformMetadata": 1,

src/coreclr/debug/runtimeinfo/datadescriptor.h

@@ -332,7 +332,7 @@ CDAC_TYPE_FIELD(MethodDesc, /*uint16*/, Flags3AndTokenRemainder, cdac_data<Metho
 CDAC_TYPE_FIELD(MethodDesc, /*uint8*/, EntryPointFlags, cdac_data<MethodDesc>::EntryPointFlags)
 CDAC_TYPE_FIELD(MethodDesc, /*pointer*/, CodeData, cdac_data<MethodDesc>::CodeData)
 #ifdef HAVE_GCCOVER
-CDAC_TYPE_FIELD(MethodDesc, /*pointer*/, GCCoverageInfo, cdac_data<MethodDesc>::GCCoverageInfo)
+CDAC_TYPE_FIELD(MethodDesc, /*pointer*/, GCCoverageInfo, MethodDesc::m_GcCover)
 #endif // HAVE_GCCOVER
 CDAC_TYPE_END(MethodDesc)
 

src/coreclr/vm/method.hpp

@@ -1910,9 +1910,6 @@ template<> struct cdac_data<MethodDesc>
     static constexpr size_t Flags3AndTokenRemainder = offsetof(MethodDesc, m_wFlags3AndTokenRemainder);
     static constexpr size_t EntryPointFlags = offsetof(MethodDesc, m_bFlags4);
     static constexpr size_t CodeData = offsetof(MethodDesc, m_codeData);
-#ifdef HAVE_GCCOVER
-    static constexpr size_t GCCoverageInfo = offsetof(MethodDesc, m_GcCover);
-#endif // HAVE_GCCOVER
 };
 
 #ifndef DACCESS_COMPILE

src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Abstractions/ContractRegistry.cs

@@ -59,8 +59,4 @@ internal abstract class ContractRegistry
     /// Gets an instance of the ReJIT contract for the target.
     /// </summary>
     public abstract IReJIT ReJIT { get; }
-    /// <summary>
-    /// Gets an instance of the GCCover contract for the target.
-    /// </summary>
-    public abstract IGCCover GCCover { get; }
 }

src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/ICodeVersions.cs

@@ -22,6 +22,8 @@ internal interface ICodeVersions : IContract
 
     public virtual TargetCodePointer GetNativeCode(NativeCodeVersionHandle codeVersionHandle) => throw new NotImplementedException();
 
+    public virtual TargetPointer GetGCStressCodeCopy(NativeCodeVersionHandle codeVersionHandle) => throw new NotImplementedException();
+
     public virtual bool CodeVersionManagerSupportsMethod(TargetPointer methodDesc) => throw new NotImplementedException();
 }
 

src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IGCCover.cs

@@ -166,7 +166,7 @@ internal interface IRuntimeTypeSystem : IContract
 
     public virtual TargetPointer GetAddressOfNativeCodeSlot(MethodDescHandle methodDesc) => throw new NotImplementedException();
 
-    public virtual TargetPointer GetGCCoverageInfo(MethodDescHandle methodDesc) => throw new NotImplementedException();
+    public virtual TargetPointer GetGCStressCodeCopy(MethodDescHandle methodDesc) => throw new NotImplementedException();
     #endregion MethodDesc inspection APIs
 }
 

src/native/managed/cdacreader/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IRuntimeTypeSystem.cs

@@ -187,7 +187,30 @@ NativeCodeVersionHandle ICodeVersions.GetActiveNativeCodeVersionForILCodeVersion
             return (ilVersionId == codeVersion.ILVersionId)
                 && ((NativeCodeVersionNodeFlags)codeVersion.Flags).HasFlag(NativeCodeVersionNodeFlags.IsActiveChild);
         });
+    }
+
+    TargetPointer ICodeVersions.GetGCStressCodeCopy(NativeCodeVersionHandle codeVersionHandle)
+    {
+        Debug.Assert(codeVersionHandle.Valid);
 
+        if (!codeVersionHandle.IsExplicit)
+        {
+            // NativeCodeVersion::GetGCCoverageInfo
+            IRuntimeTypeSystem rts = _target.Contracts.RuntimeTypeSystem;
+            MethodDescHandle md = rts.GetMethodDescHandle(codeVersionHandle.MethodDescAddress);
+            return rts.GetGCStressCodeCopy(md);
+        }
+        else
+        {
+            // NativeCodeVersionNode::GetGCCoverageInfo
+            NativeCodeVersionNode codeVersionNode = AsNode(codeVersionHandle);
+            if (codeVersionNode.GCCoverageInfo is TargetPointer gcCoverageInfoAddr)
+            {
+                Target.TypeInfo gcCoverageInfoType = _target.GetTypeInfo(DataType.GCCoverageInfo);
+                return gcCoverageInfoAddr + (ulong)gcCoverageInfoType.Fields["SavedCode"].Offset;
+            }
+            return TargetPointer.Null;
+        }
     }
 
     [Flags]