Provide System linkage implementations of entry point APIs

Implement `entryPointFromCompiledMethod` and `entryPointFromInterpretedMethod`
for System linkage classes on RISC-V.

Signed-off-by: Daryl Maier <maier@ca.ibm.com>

compiler/riscv/codegen/RVSystemLinkage.cpp

@@ -879,3 +879,13 @@ TR::Register *TR::RVSystemLinkage::buildDispatch(TR::Node *callNode)
    return retReg;
    }
 
+intptr_t TR::RVSystemLinkage::entryPointFromCompiledMethod()
+   {
+   return reinterpret_cast<intptr_t>(cg()->getCodeStart());
+   }
+
+intptr_t TR::RVSystemLinkage::entryPointFromInterpretedMethod()
+   {
+   return reinterpret_cast<intptr_t>(cg()->getCodeStart());
+   }
+

compiler/riscv/codegen/RVSystemLinkage.hpp

@@ -130,6 +130,34 @@ class RVSystemLinkage : public TR::Linkage
       return buildDispatch(callNode);
       }
 
+   /**
+    * @brief Provides the entry point in a method to use when that method is invoked
+    *        from a method compiled with the same linkage.
+    *
+    * @details
+    *    When asked on the method currently being compiled, this API will return 0 if
+    *    asked before code memory has been allocated.
+    *
+    *    The compiled method entry point may be the same as the interpreter entry point.
+    *
+    * @return The entry point for compiled methods to use; 0 if the entry point is unknown
+    */
+   virtual intptr_t entryPointFromCompiledMethod();
+
+   /**
+    * @brief Provides the entry point in a method to use when that method is invoked
+    *        from an interpreter using the same linkage.
+    *
+    * @details
+    *    When asked on the method currently being compiled, this API will return 0 if
+    *    asked before code memory has been allocated.
+    *
+    *    The compiled method entry point may be the same as the interpreter entry point.
+    *
+    * @return The entry point for interpreted methods to use; 0 if the entry point is unknown
+    */
+   virtual intptr_t entryPointFromInterpretedMethod();
+
    };
 
 }