[RISC-V] Add RiscV64 arch to tests/JIT/Stress/ABI/ (#103830)

Author: t-mustafin

src/tests/JIT/Stress/ABI/ABIs.cs

@@ -186,4 +186,34 @@ public int ApproximateArgStackAreaSize(List<TypeEx> parameters)
             return size;
         }
     }
+
+    internal class Riscv64Abi : IAbi
+    {
+        // For Riscv64 structs larger than 16 bytes are passed by-ref and will
+        // inhibit tailcalls, so we exclude those.
+        public Type[] TailCalleeCandidateArgTypes { get; } =
+            new[]
+            {
+                typeof(byte), typeof(short), typeof(int), typeof(long),
+                typeof(float), typeof(double), typeof(Int128),
+                typeof(Vector<int>), typeof(Vector128<int>),
+                typeof(S1P), typeof(S2P), typeof(S2U), typeof(S3U),
+                typeof(S4P), typeof(S4U), typeof(S5U), typeof(S6U),
+                typeof(S7U), typeof(S8P), typeof(S8U), typeof(S9U),
+                typeof(S10U), typeof(S11U), typeof(S12U), typeof(S13U),
+                typeof(S14U), typeof(S15U), typeof(S16U),
+                typeof(Hfa1), typeof(I128_1)
+            };
+
+        public CallingConvention[] PInvokeConventions { get; } = { CallingConvention.Cdecl };
+
+        public int ApproximateArgStackAreaSize(List<TypeEx> parameters)
+        {
+            int size = 0;
+            foreach (TypeEx pm in parameters)
+                size += Util.RoundUp(pm.Size, 8);
+
+            return size;
+        }
+    }
 }

src/tests/JIT/Stress/ABI/Program.cs

@@ -408,6 +408,11 @@ private static IAbi SelectAbi()
                     Console.WriteLine("Selecting armhf ABI.");
                     return new Arm32Abi();
                 }
+                if (RuntimeInformation.ProcessArchitecture == Architecture.RiscV64)
+                {
+                    Console.WriteLine("Selecting riscv64 ABI.");
+                    return new Riscv64Abi();
+                }
 
                 Trace.Assert(RuntimeInformation.ProcessArchitecture == Architecture.X64);
                 Console.WriteLine("Selecting SysV ABI");