Revert "Have Unsafe.Subtract and Unsafe.SubtractByteOffset be intrinsic"

This reverts commit 2301adc.

Author: tannergooding

src/coreclr/jit/importer.cpp

@@ -4834,8 +4834,8 @@ GenTree* Compiler::impSRCSUnsafeIntrinsic(NamedIntrinsic        intrinsic,
                 tmp = op2;
             }
 
-            type = impGetByRefResultType(GT_ADD, /* uns */ false, &op1, &tmp);
-            return gtNewOperNode(GT_ADD, type, op1, tmp);
+            type = impGetByRefResultType(GT_ADD, /* uns */ false, &tmp, &op1);
+            return gtNewOperNode(GT_ADD, type, tmp, op1);
         }
 
         case NI_SRCS_UNSAFE_AddByteOffset:
@@ -5139,33 +5139,7 @@ GenTree* Compiler::impSRCSUnsafeIntrinsic(NamedIntrinsic        intrinsic,
             // sub
             // ret
 
-            GenTree* op2 = impPopStack().val;
-            GenTree* op1 = impPopStack().val;
-            impBashVarAddrsToI(op1, op2);
-
-            GenTree*  tmp  = nullptr;
-            var_types type = TYP_UNKNOWN;
-
-            unsigned classSize = info.compCompHnd->getClassSize(sig->sigInst.methInst[0]);
-
-            if (classSize != 1)
-            {
-                GenTree* size = gtNewIconNode(classSize, TYP_INT);
-
-#ifdef TARGET_64BIT
-                size = gtNewCastNode(TYP_I_IMPL, size, /* uns */ false, TYP_I_IMPL);
-#endif
-
-                type = impGetByRefResultType(GT_MUL, /* uns */ false, &op2, &size);
-                tmp  = new (this, GT_CALL) GenTreeOp(GT_MUL, type, op2, size DEBUGARG(/* largeNode */ true));
-            }
-            else
-            {
-                tmp = op2;
-            }
-
-            type = impGetByRefResultType(GT_SUB, /* uns */ false, &op1, &tmp);
-            return gtNewOperNode(GT_SUB, type, op1, tmp);
+            return nullptr;
         }
 
         case NI_SRCS_UNSAFE_SubtractByteOffset:
@@ -5177,12 +5151,7 @@ GenTree* Compiler::impSRCSUnsafeIntrinsic(NamedIntrinsic        intrinsic,
             // sub
             // ret
 
-            GenTree* op2 = impPopStack().val;
-            GenTree* op1 = impPopStack().val;
-            impBashVarAddrsToI(op1, op2);
-
-            var_types type = impGetByRefResultType(GT_SUB, /* uns */ false, &op1, &op2);
-            return gtNewOperNode(GT_SUB, type, op1, op2);
+            return nullptr;
         }
 
         case NI_SRCS_UNSAFE_Unbox: