Fix buffer overrun in JIT for Vector256<T> types on ARM64

src/coreclr/src/jit/compiler.h

@@ -1738,6 +1738,10 @@ struct fgArgTabEntry
 #else
         unsigned int regSize = 1;
 #endif
+
+        if (numRegs > MAX_ARG_REG_COUNT)
+            NO_WAY("Multireg argument exceeds the maximum length");
+
         for (unsigned int regIndex = 1; regIndex < numRegs; regIndex++)
         {
             argReg = (regNumber)(argReg + regSize);

src/coreclr/src/tools/Common/Compiler/VectorFieldLayoutAlgorithm.cs

@@ -96,7 +96,6 @@ public override ValueTypeShapeCharacteristics ComputeValueTypeShapeCharacteristi
                 {
                     8 => ValueTypeShapeCharacteristics.Vector64Aggregate,
                     16 => ValueTypeShapeCharacteristics.Vector128Aggregate,
-                    32 => ValueTypeShapeCharacteristics.Vector256Aggregate,
                     _ => ValueTypeShapeCharacteristics.None
                 };
             }
@@ -107,9 +106,7 @@ public static bool IsVectorType(DefType type)
         {
             return type.IsIntrinsic &&
                 type.Namespace == "System.Runtime.Intrinsics" &&
-                (type.Name == "Vector64`1" ||
-                type.Name == "Vector128`1" ||
-                type.Name == "Vector256`1") &&
+                ((type.Name == "Vector64`1") || (type.Name == "Vector128`1")) &&
                 type.Instantiation[0].IsPrimitive;
         }
     }

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

@@ -2206,15 +2206,14 @@ private CorInfoType getHFAType(CORINFO_CLASS_STRUCT_* hClass)
             var type = (DefType)HandleToObject(hClass);
 
             // For 8-byte vectors return CORINFO_TYPE_DOUBLE, which is mapped by JIT to SIMD8.
-            // Otherwise, return CORINFO_TYPE_VALUECLASS, which is mapped by JIT to SIMD16.
+            // For 16-byte vectors return CORINFO_TYPE_VALUECLASS, which is mapped by JIT to SIMD16.
             // See MethodTable::GetHFAType and Compiler::GetHfaType.
             return (type.ValueTypeShapeCharacteristics & ValueTypeShapeCharacteristics.AggregateMask) switch
             {
                 ValueTypeShapeCharacteristics.Float32Aggregate => CorInfoType.CORINFO_TYPE_FLOAT,
                 ValueTypeShapeCharacteristics.Float64Aggregate => CorInfoType.CORINFO_TYPE_DOUBLE,
                 ValueTypeShapeCharacteristics.Vector64Aggregate => CorInfoType.CORINFO_TYPE_DOUBLE,
                 ValueTypeShapeCharacteristics.Vector128Aggregate => CorInfoType.CORINFO_TYPE_VALUECLASS,
-                ValueTypeShapeCharacteristics.Vector256Aggregate => CorInfoType.CORINFO_TYPE_VALUECLASS,
                 _ => CorInfoType.CORINFO_TYPE_UNDEF
             };
         }

src/coreclr/src/tools/Common/TypeSystem/Common/DefType.FieldLayout.cs

@@ -321,7 +321,6 @@ public int GetHomogeneousAggregateElementSize()
                 ValueTypeShapeCharacteristics.Float64Aggregate => 8,
                 ValueTypeShapeCharacteristics.Vector64Aggregate => 8,
                 ValueTypeShapeCharacteristics.Vector128Aggregate => 16,
-                ValueTypeShapeCharacteristics.Vector256Aggregate => 16,
                 _ => throw new InvalidOperationException()
             };
         }

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

@@ -132,11 +132,6 @@ public enum ValueTypeShapeCharacteristics
         /// </summary>
         Vector128Aggregate = 0x08,
 
-        /// <summary>
-        /// The type is an aggregate of 256-bit short-vector values.
-        /// </summary>
-        Vector256Aggregate = 0x10,
-
         /// <summary>
         /// The mask for homogeneous aggregates of floating-point values.
         /// </summary>
@@ -145,7 +140,7 @@ public enum ValueTypeShapeCharacteristics
         /// <summary>
         /// The mask for homogeneous aggregates of short-vector values.
         /// </summary>
-        ShortVectorAggregateMask = Vector64Aggregate | Vector128Aggregate | Vector256Aggregate,
+        ShortVectorAggregateMask = Vector64Aggregate | Vector128Aggregate,
 
         /// <summary>
         /// The mask for homogeneous aggregates.

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

@@ -906,7 +906,6 @@ private ValueTypeShapeCharacteristics ComputeHomogeneousAggregateCharacteristic(
                         ValueTypeShapeCharacteristics.Float64Aggregate => 8,
                         ValueTypeShapeCharacteristics.Vector64Aggregate => 8,
                         ValueTypeShapeCharacteristics.Vector128Aggregate => 16,
-                        ValueTypeShapeCharacteristics.Vector256Aggregate => 32,
                         _ => throw new ArgumentOutOfRangeException()
                     };
 

src/coreclr/src/tools/crossgen2/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/TypeFixupSignature.cs

@@ -88,7 +88,6 @@ private static void EncodeTypeLayout(ObjectDataSignatureBuilder dataBuilder, Typ
                     ValueTypeShapeCharacteristics.Vector64Aggregate => CorElementType.ELEMENT_TYPE_R8,
                     // See MethodTable::GetHFAType
                     ValueTypeShapeCharacteristics.Vector128Aggregate => CorElementType.ELEMENT_TYPE_VALUETYPE,
-                    ValueTypeShapeCharacteristics.Vector256Aggregate => CorElementType.ELEMENT_TYPE_VALUETYPE,
                     _ => CorElementType.Invalid
                 };
                 dataBuilder.EmitUInt((uint)elementType);

src/coreclr/src/vm/class.cpp

@@ -1195,10 +1195,6 @@ int MethodTable::GetVectorSize()
         {
             vectorSize = 16;
         }
-        else if (strcmp(className, "Vector256`1") == 0)
-        {
-            vectorSize = 32;
-        }
         else if (strcmp(className, "Vector64`1") == 0)
         {
             vectorSize = 8;