From b9672c066949c7ea6fe86584ca2e0eedb72d81ae Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Wed, 20 Jan 2021 18:21:44 -0500
Subject: [PATCH] Gets beyond a prima facie convincing JSR/RET.

---
 InstructionSets/M50740/Executor.cpp | 12 ++++++++++++
 InstructionSets/M50740/Executor.hpp |  1 +
 2 files changed, 13 insertions(+)

diff --git a/InstructionSets/M50740/Executor.cpp b/InstructionSets/M50740/Executor.cpp
index 79c1c6b19..20033027c 100644
--- a/InstructionSets/M50740/Executor.cpp
+++ b/InstructionSets/M50740/Executor.cpp
@@ -90,6 +90,11 @@ void Executor::push(uint8_t value) {
 	--s_;
 }
 
+uint8_t Executor::pull() {
+	++s_;
+	return read(s_);
+}
+
 template <Operation operation, AddressingMode addressing_mode> void Executor::perform() {
 	// Deal with all modes that don't access memory up here;
 	// those that access memory will go through a slightly longer
@@ -264,6 +269,13 @@ template <Operation operation> void Executor::perform(uint8_t *operand [[maybe_u
 		case Operation::DEC:	--*operand; set_nz(*operand);	break;
 		case Operation::INC:	++*operand; set_nz(*operand);	break;
 
+		case Operation::RTS: {
+			uint16_t target = pull();
+			target |= pull() << 8;
+			++target;
+			set_program_counter(target);
+		} break;
+
 		/*
 			Already removed from the instruction stream:
 
diff --git a/InstructionSets/M50740/Executor.hpp b/InstructionSets/M50740/Executor.hpp
index 0a5f4149c..5c99623c5 100644
--- a/InstructionSets/M50740/Executor.hpp
+++ b/InstructionSets/M50740/Executor.hpp
@@ -121,6 +121,7 @@ class Executor: public CachingExecutor {
 		inline uint8_t read(uint16_t address);
 		inline void write(uint16_t address, uint8_t value);
 		inline void push(uint8_t value);
+		inline uint8_t pull();
 };
 
 }