RuntimeHelpers.CreateSpan<T> (#61079)

Implement `RuntimeHelpers.CreateSpan<T>` #60948 

Implementation provides for
- Both non-intrinsic and intrinsic implementations in CoreCLR
- Non-intrinsic implementation in Mono
  - Mono implementation also implements untested big endian support

Co-authored-by: Aaron Robinson <arobins@microsoft.com>
Co-authored-by: Jan Kotas <jkotas@microsoft.com>

src/coreclr/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.CoreCLR.cs

@@ -17,6 +17,12 @@ public static partial class RuntimeHelpers
         [MethodImpl(MethodImplOptions.InternalCall)]
         public static extern void InitializeArray(Array array, RuntimeFieldHandle fldHandle);
 
+        [MethodImpl(MethodImplOptions.InternalCall)]
+        private static extern unsafe void* GetSpanDataFrom(
+            RuntimeFieldHandle fldHandle,
+            RuntimeTypeHandle targetTypeHandle,
+            out int count);
+
         // GetObjectValue is intended to allow value classes to be manipulated as 'Object'
         // but have aliasing behavior of a value class.  The intent is that you would use
         // this function just before an assignment to a variable of type 'Object'.  If the

src/coreclr/classlibnative/bcltype/arraynative.cpp

@@ -1153,3 +1153,46 @@ FCIMPL2_IV(void, ArrayNative::InitializeArray, ArrayBase* pArrayRef, FCALLRuntim
     HELPER_METHOD_FRAME_END();
 }
 FCIMPLEND
+
+FCIMPL3(void*, ArrayNative::GetSpanDataFrom, FCALLRuntimeFieldHandle structField, FCALLRuntimeTypeHandle targetType, INT32* count)
+{
+    FCALL_CONTRACT;
+    struct
+    {
+        REFLECTFIELDREF refField;
+    } gc;
+    gc.refField = (REFLECTFIELDREF)ObjectToOBJECTREF(FCALL_RFH_TO_REFLECTFIELD(structField));
+    void* data;
+    HELPER_METHOD_FRAME_BEGIN_RET_1(gc);
+
+    FieldDesc* pField = (FieldDesc*)gc.refField->GetField();
+
+    if (!pField->IsRVA())
+        COMPlusThrow(kArgumentException);
+
+    TypeHandle targetTypeHandle = FCALL_RTH_TO_REFLECTCLASS(targetType)->GetType();
+    if (!CorTypeInfo::IsPrimitiveType(targetTypeHandle.GetSignatureCorElementType()) && !targetTypeHandle.IsEnum())
+        COMPlusThrow(kArgumentException);
+
+    DWORD totalSize = pField->LoadSize();
+    DWORD targetTypeSize = targetTypeHandle.GetSize();
+
+    // Report the RVA field to the logger.
+    g_IBCLogger.LogRVADataAccess(pField);
+
+    _ASSERTE(data != NULL && count != NULL);
+    data = pField->GetStaticAddressHandle(NULL);
+
+    if (AlignUp((UINT_PTR)data, targetTypeSize) != (UINT_PTR)data)
+        COMPlusThrow(kArgumentException);
+
+    *count = (INT32)totalSize / targetTypeSize;
+
+#if BIGENDIAN
+    COMPlusThrow(kPlatformNotSupportedException);
+#endif
+
+   HELPER_METHOD_FRAME_END();
+   return data;
+}
+FCIMPLEND

src/coreclr/classlibnative/bcltype/arraynative.h

@@ -14,6 +14,7 @@
 #define _ARRAYNATIVE_H_
 
 #include "fcall.h"
+#include "runtimehandles.h"
 
 struct FCALLRuntimeFieldHandle
 {
@@ -45,6 +46,10 @@ class ArrayNative
     // to a field.
     static FCDECL2_IV(void, InitializeArray, ArrayBase* vArrayRef, FCALLRuntimeFieldHandle structField);
 
+    // This method will acquire data to create a span from a TypeHandle
+    // to a field.
+    static FCDECL3(void*, GetSpanDataFrom, FCALLRuntimeFieldHandle structField, FCALLRuntimeTypeHandle targetType, INT32* count);
+
 private:
     // Helper for CreateInstance
     static void CheckElementType(TypeHandle elementType);

src/coreclr/jit/compiler.h

@@ -4483,6 +4483,7 @@ class Compiler
                                      bool                 readonlyCall,
                                      CorInfoIntrinsics    intrinsicID);
     GenTree* impInitializeArrayIntrinsic(CORINFO_SIG_INFO* sig);
+    GenTree* impCreateSpanIntrinsic(CORINFO_SIG_INFO* sig);
 
     GenTree* impKeepAliveIntrinsic(GenTree* objToKeepAlive);
 

src/coreclr/jit/importer.cpp

@@ -3652,6 +3652,120 @@ const char* Compiler::impGetIntrinsicName(CorInfoIntrinsics intrinsicID)
 
 #endif // DEBUG
 
+GenTree* Compiler::impCreateSpanIntrinsic(CORINFO_SIG_INFO* sig)
+{
+    assert(sig->numArgs == 1);
+    assert(sig->sigInst.methInstCount == 1);
+
+    GenTree* fieldTokenNode = impStackTop(0).val;
+
+    //
+    // Verify that the field token is known and valid.  Note that it's also
+    // possible for the token to come from reflection, in which case we cannot do
+    // the optimization and must therefore revert to calling the helper.  You can
+    // see an example of this in bvt\DynIL\initarray2.exe (in Main).
+    //
+
+    // Check to see if the ldtoken helper call is what we see here.
+    if (fieldTokenNode->gtOper != GT_CALL || (fieldTokenNode->AsCall()->gtCallType != CT_HELPER) ||
+        (fieldTokenNode->AsCall()->gtCallMethHnd != eeFindHelper(CORINFO_HELP_FIELDDESC_TO_STUBRUNTIMEFIELD)))
+    {
+        return nullptr;
+    }
+
+    // Strip helper call away
+    fieldTokenNode = fieldTokenNode->AsCall()->gtCallArgs->GetNode();
+    if (fieldTokenNode->gtOper == GT_IND)
+    {
+        fieldTokenNode = fieldTokenNode->AsOp()->gtOp1;
+    }
+
+    // Check for constant
+    if (fieldTokenNode->gtOper != GT_CNS_INT)
+    {
+        return nullptr;
+    }
+
+    CORINFO_FIELD_HANDLE fieldToken = (CORINFO_FIELD_HANDLE)fieldTokenNode->AsIntCon()->gtCompileTimeHandle;
+    if (!fieldTokenNode->IsIconHandle(GTF_ICON_FIELD_HDL) || (fieldToken == nullptr))
+    {
+        return nullptr;
+    }
+
+    CORINFO_CLASS_HANDLE fieldOwnerHnd = info.compCompHnd->getFieldClass(fieldToken);
+
+    CORINFO_CLASS_HANDLE fieldClsHnd;
+    var_types            fieldElementType =
+        JITtype2varType(info.compCompHnd->getFieldType(fieldToken, &fieldClsHnd, fieldOwnerHnd));
+    unsigned totalFieldSize;
+
+    // Most static initialization data fields are of some structure, but it is possible for them to be of various
+    // primitive types as well
+    if (fieldElementType == var_types::TYP_STRUCT)
+    {
+        totalFieldSize = info.compCompHnd->getClassSize(fieldClsHnd);
+    }
+    else
+    {
+        totalFieldSize = genTypeSize(fieldElementType);
+    }
+
+    // Limit to primitive or enum type - see ArrayNative::GetSpanDataFrom()
+    CORINFO_CLASS_HANDLE targetElemHnd = sig->sigInst.methInst[0];
+    if (info.compCompHnd->getTypeForPrimitiveValueClass(targetElemHnd) == CORINFO_TYPE_UNDEF)
+    {
+        return nullptr;
+    }
+
+    const unsigned targetElemSize = info.compCompHnd->getClassSize(targetElemHnd);
+    assert(targetElemSize != 0);
+
+    const unsigned count = totalFieldSize / targetElemSize;
+    if (count == 0)
+    {
+        return nullptr;
+    }
+
+    void* data = info.compCompHnd->getArrayInitializationData(fieldToken, totalFieldSize);
+    if (!data)
+    {
+        return nullptr;
+    }
+
+    //
+    // Ready to commit to the work
+    //
+
+    impPopStack();
+
+    // Turn count and pointer value into constants.
+    GenTree* lengthValue  = gtNewIconNode(count, TYP_INT);
+    GenTree* pointerValue = gtNewIconHandleNode((size_t)data, GTF_ICON_CONST_PTR);
+
+    // Construct ReadOnlySpan<T> to return.
+    CORINFO_CLASS_HANDLE spanHnd     = sig->retTypeClass;
+    unsigned             spanTempNum = lvaGrabTemp(true DEBUGARG("ReadOnlySpan<T> for CreateSpan<T>"));
+    lvaSetStruct(spanTempNum, spanHnd, false);
+
+    CORINFO_FIELD_HANDLE pointerFieldHnd = info.compCompHnd->getFieldInClass(spanHnd, 0);
+    CORINFO_FIELD_HANDLE lengthFieldHnd  = info.compCompHnd->getFieldInClass(spanHnd, 1);
+
+    GenTreeLclFld* pointerField = gtNewLclFldNode(spanTempNum, TYP_BYREF, 0);
+    pointerField->SetFieldSeq(GetFieldSeqStore()->CreateSingleton(pointerFieldHnd));
+    GenTree* pointerFieldAsg = gtNewAssignNode(pointerField, pointerValue);
+
+    GenTreeLclFld* lengthField = gtNewLclFldNode(spanTempNum, TYP_INT, TARGET_POINTER_SIZE);
+    lengthField->SetFieldSeq(GetFieldSeqStore()->CreateSingleton(lengthFieldHnd));
+    GenTree* lengthFieldAsg = gtNewAssignNode(lengthField, lengthValue);
+
+    // Now append a few statements the initialize the span
+    impAppendTree(lengthFieldAsg, (unsigned)CHECK_SPILL_NONE, impCurStmtDI);
+    impAppendTree(pointerFieldAsg, (unsigned)CHECK_SPILL_NONE, impCurStmtDI);
+
+    // And finally create a tree that points at the span.
+    return impCreateLocalNode(spanTempNum DEBUGARG(0));
+}
+
 //------------------------------------------------------------------------
 // impIntrinsic: possibly expand intrinsic call into alternate IR sequence
 //
@@ -3811,6 +3925,12 @@ GenTree* Compiler::impIntrinsic(GenTree*                newobjThis,
         return new (this, GT_LABEL) GenTree(GT_LABEL, TYP_I_IMPL);
     }
 
+    if ((ni == NI_System_Runtime_CompilerServices_RuntimeHelpers_CreateSpan) && IsTargetAbi(CORINFO_CORERT_ABI))
+    {
+        // CreateSpan must be expanded for NativeAOT
+        mustExpand = true;
+    }
+
     GenTree* retNode = nullptr;
 
     // Under debug and minopts, only expand what is required.
@@ -4079,6 +4199,12 @@ GenTree* Compiler::impIntrinsic(GenTree*                newobjThis,
                 break;
             }
 
+            case NI_System_Runtime_CompilerServices_RuntimeHelpers_CreateSpan:
+            {
+                retNode = impCreateSpanIntrinsic(sig);
+                break;
+            }
+
             case NI_System_Span_get_Item:
             case NI_System_ReadOnlySpan_get_Item:
             {
@@ -5195,6 +5321,14 @@ NamedIntrinsic Compiler::lookupNamedIntrinsic(CORINFO_METHOD_HANDLE method)
         result = SimdAsHWIntrinsicInfo::lookupId(&sig, className, methodName, enclosingClassName, sizeOfVectorT);
     }
 #endif // FEATURE_HW_INTRINSICS
+    else if ((strcmp(namespaceName, "System.Runtime.CompilerServices") == 0) &&
+             (strcmp(className, "RuntimeHelpers") == 0))
+    {
+        if (strcmp(methodName, "CreateSpan") == 0)
+        {
+            result = NI_System_Runtime_CompilerServices_RuntimeHelpers_CreateSpan;
+        }
+    }
     else if (strncmp(namespaceName, "System.Runtime.Intrinsics", 25) == 0)
     {
         // We go down this path even when FEATURE_HW_INTRINSICS isn't enabled

src/coreclr/jit/namedintrinsiclist.h

@@ -61,6 +61,8 @@ enum NamedIntrinsic : unsigned short
     NI_System_Array_GetUpperBound,
     NI_System_Object_MemberwiseClone,
 
+    NI_System_Runtime_CompilerServices_RuntimeHelpers_CreateSpan,
+
     NI_System_String_get_Chars,
     NI_System_String_get_Length,
     NI_System_Span_get_Item,

src/coreclr/tools/Common/JitInterface/CorInfoImpl.cs

@@ -576,6 +576,8 @@ private void CompileMethodCleanup()
             _actualInstructionSetUnsupported = default(InstructionSetFlags);
 #endif
 
+            _instantiationToJitVisibleInstantiation = null;
+
             _pgoResults.Clear();
         }
 
@@ -662,6 +664,25 @@ private bool Get_CORINFO_METHOD_INFO(MethodDesc method, MethodIL methodIL, CORIN
             return true;
         }
 
+        private Dictionary<Instantiation, IntPtr[]> _instantiationToJitVisibleInstantiation = null;
+        private CORINFO_CLASS_STRUCT_** GetJitInstantiation(Instantiation inst)
+        {
+            IntPtr [] jitVisibleInstantiation;
+            if (_instantiationToJitVisibleInstantiation == null)
+            {
+                _instantiationToJitVisibleInstantiation = new Dictionary<Instantiation, IntPtr[]>();
+            }
+
+            if (!_instantiationToJitVisibleInstantiation.TryGetValue(inst, out jitVisibleInstantiation))
+            {
+                jitVisibleInstantiation =  new IntPtr[inst.Length];
+                for (int i = 0; i < inst.Length; i++)
+                    jitVisibleInstantiation[i] = (IntPtr)ObjectToHandle(inst[i]);
+                _instantiationToJitVisibleInstantiation.Add(inst, jitVisibleInstantiation);
+            }
+            return (CORINFO_CLASS_STRUCT_**)GetPin(jitVisibleInstantiation);
+        }
+
         private void Get_CORINFO_SIG_INFO(MethodDesc method, CORINFO_SIG_INFO* sig, bool suppressHiddenArgument = false)
         {
             Get_CORINFO_SIG_INFO(method.Signature, sig);
@@ -684,12 +705,15 @@ private void Get_CORINFO_SIG_INFO(MethodDesc method, CORINFO_SIG_INFO* sig, bool
                 // JIT doesn't care what the instantiation is and this is expensive.
                 Instantiation owningTypeInst = method.OwningType.Instantiation;
                 sig->sigInst.classInstCount = (uint)owningTypeInst.Length;
-                if (owningTypeInst.Length > 0)
+                if (owningTypeInst.Length != 0)
+                {
+                    sig->sigInst.classInst = GetJitInstantiation(owningTypeInst);
+                }
+
+                sig->sigInst.methInstCount = (uint)method.Instantiation.Length;
+                if (method.Instantiation.Length != 0)
                 {
-                    var classInst = new IntPtr[owningTypeInst.Length];
-                    for (int i = 0; i < owningTypeInst.Length; i++)
-                        classInst[i] = (IntPtr)ObjectToHandle(owningTypeInst[i]);
-                    sig->sigInst.classInst = (CORINFO_CLASS_STRUCT_**)GetPin(classInst);
+                    sig->sigInst.methInst = GetJitInstantiation(method.Instantiation);
                 }
             }
 

src/coreclr/tools/Common/TypeSystem/Common/Instantiation.cs

@@ -11,7 +11,7 @@ namespace Internal.TypeSystem
     /// Represents a generic instantiation - a collection of generic parameters
     /// or arguments of a generic type or a generic method.
     /// </summary>
-    public struct Instantiation
+    public struct Instantiation : IEquatable<Instantiation>
     {
         private TypeDesc[] _genericParameters;
 
@@ -113,5 +113,25 @@ public bool MoveNext()
                 return true;
             }
         }
+
+        public bool Equals(Instantiation other)
+        {
+            if (_genericParameters.Length != other._genericParameters.Length)
+                return false;
+
+            for (int i = 0; i < _genericParameters.Length; i++)
+            {
+                if (_genericParameters[i] != other._genericParameters[i])
+                    return false;
+            }
+            return true;
+        }
+        public override bool Equals(object o)
+        {
+            if (o is Instantiation inst)
+                return Equals(inst);
+            return false;
+        }
+        public override int GetHashCode() => ComputeGenericInstanceHashCode(1);
     }
 }

src/coreclr/vm/ecalllist.h

@@ -626,6 +626,7 @@ FCFuncEnd()
 FCFuncStart(gRuntimeHelpers)
     FCFuncElement("GetObjectValue", ObjectNative::GetObjectValue)
     FCIntrinsic("InitializeArray", ArrayNative::InitializeArray, CORINFO_INTRINSIC_InitializeArray)
+    FCFuncElement("GetSpanDataFrom", ArrayNative::GetSpanDataFrom)
     FCFuncElement("PrepareDelegate", ReflectionInvocation::PrepareDelegate)
     FCFuncElement("GetHashCode", ObjectNative::GetHashCode)
     FCFuncElement("Equals", ObjectNative::Equals)

src/coreclr/vm/runtimehandles.h

@@ -113,8 +113,8 @@ typedef RuntimeTypeHandle FCALLRuntimeTypeHandle;
 #define FCALL_RTH_TO_REFLECTCLASS(x) (x).pRuntimeTypeDONOTUSEDIRECTLY
 
 class RuntimeTypeHandle {
-    ReflectClassBaseObject *pRuntimeTypeDONOTUSEDIRECTLY;
 public:
+    ReflectClassBaseObject *pRuntimeTypeDONOTUSEDIRECTLY;
 
     // Static method on RuntimeTypeHandle
     static FCDECL1(Object*, AllocateComObject, void* pClassFactory);

src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs

@@ -109,5 +109,13 @@ public static void PrepareConstrainedRegionsNoOP()
         internal static bool IsPrimitiveType(this CorElementType et)
             // COR_ELEMENT_TYPE_I1,I2,I4,I8,U1,U2,U4,U8,R4,R8,I,U,CHAR,BOOLEAN
             => ((1 << (int)et) & 0b_0011_0000_0000_0011_1111_1111_1100) != 0;
+
+        /// <summary>Provide a fast way to access constant data stored in a module as a ReadOnlySpan{T}</summary>
+        /// <param name="fldHandle">A field handle that specifies the location of the data to be referred to by the ReadOnlySpan{T}. The Rva of the field must be aligned on a natural boundary of type T</param>
+        /// <returns>A ReadOnlySpan{T} of the data stored in the field</returns>
+        /// <exception cref="ArgumentException"><paramref name="fldHandle"/> does not refer to a field which is an Rva, is misaligned, or T is of an invalid type.</exception>
+        /// <remarks>This method is intended for compiler user rather than use directly in code. T must be one of byte, sbyte, char, short, ushort, int, long, ulong, float, or double.</remarks>
+        [Intrinsic]
+        public static unsafe ReadOnlySpan<T> CreateSpan<T>(RuntimeFieldHandle fldHandle) => new ReadOnlySpan<T>(GetSpanDataFrom(fldHandle, typeof(T).TypeHandle, out int length), length);
     }
 }

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -13203,6 +13203,7 @@ public static void ExecuteCodeWithGuaranteedCleanup(System.Runtime.CompilerServi
         public static T[] GetSubArray<T>(T[] array, System.Range range) { throw null; }
         public static object GetUninitializedObject([System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.NonPublicConstructors | System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicConstructors)] System.Type type) { throw null; }
         public static void InitializeArray(System.Array array, System.RuntimeFieldHandle fldHandle) { }
+        public static ReadOnlySpan<T> CreateSpan<T>(System.RuntimeFieldHandle fldHandle) { throw null; }
         public static bool IsReferenceOrContainsReferences<T>() { throw null; }
         [System.ObsoleteAttribute("The Constrained Execution Region (CER) feature is not supported.", DiagnosticId = "SYSLIB0004", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
         public static void PrepareConstrainedRegions() { }