From 90f49a6e73ca1843d63e0ae61b0be4c9418d9dbf Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Wed, 18 Oct 2023 13:15:00 -0400
Subject: [PATCH] Implement JMP.

---
 .../Implementation/PerformImplementation.hpp  | 43 ++++++++++++++++++-
 OSBindings/Mac/Clock SignalTests/8088Tests.mm | 22 +++++++---
 2 files changed, 59 insertions(+), 6 deletions(-)

diff --git a/InstructionSets/x86/Implementation/PerformImplementation.hpp b/InstructionSets/x86/Implementation/PerformImplementation.hpp
index 735337fd2..c4d2e00a2 100644
--- a/InstructionSets/x86/Implementation/PerformImplementation.hpp
+++ b/InstructionSets/x86/Implementation/PerformImplementation.hpp
@@ -779,6 +779,11 @@ void call_absolute(IntT target, FlowControllerT &flow_controller) {
 	flow_controller.call(target);
 }
 
+template <typename IntT, typename FlowControllerT>
+void jump_absolute(IntT target, FlowControllerT &flow_controller) {
+	flow_controller.jump(target);
+}
+
 template <Model model, typename InstructionT, typename FlowControllerT, typename RegistersT, typename MemoryT>
 void call_far(InstructionT &instruction,
 	FlowControllerT &flow_controller,
@@ -811,6 +816,38 @@ void call_far(InstructionT &instruction,
 	flow_controller.call(segment, offset);
 }
 
+template <Model model, typename InstructionT, typename FlowControllerT, typename RegistersT, typename MemoryT>
+void jump_far(InstructionT &instruction,
+	FlowControllerT &flow_controller,
+	RegistersT &registers,
+	MemoryT &memory
+) {
+	// TODO: eliminate 16-bit assumption below.
+	uint16_t source_address = 0;
+	const auto pointer = instruction.destination();
+	switch(pointer.template source<false>()) {
+		default:
+		case Source::Immediate:	flow_controller.call(instruction.segment(), instruction.offset());	return;
+
+		case Source::Indirect:
+			source_address = address<model, Source::Indirect, uint16_t>(instruction, pointer, registers, memory);
+		break;
+		case Source::IndirectNoBase:
+			source_address = address<model, Source::IndirectNoBase, uint16_t>(instruction, pointer, registers, memory);
+		break;
+		case Source::DirectAddress:
+			source_address = address<model, Source::DirectAddress, uint16_t>(instruction, pointer, registers, memory);
+		break;
+	}
+
+	const Source source_segment = pointer.segment(instruction.segment_override());
+
+	const uint16_t offset = memory.template access<uint16_t>(source_segment, source_address);
+	source_address += 2;
+	const uint16_t segment = memory.template access<uint16_t>(source_segment, source_address);
+	flow_controller.jump(segment, offset);
+}
+
 template <typename FlowControllerT, typename RegistersT, typename MemoryT>
 void iret(RegistersT &registers, FlowControllerT &flow_controller, MemoryT &memory, Status &status) {
 	// TODO: all modes other than 16-bit real mode.
@@ -1412,7 +1449,11 @@ template <
 			Primitive::call_far<model>(instruction, flow_controller, registers, memory);
 		return;
 
-		case Operation::IRET:		Primitive::iret(registers, flow_controller, memory, status);				return;
+		case Operation::JMPrel:	jcc(true);																		return;
+		case Operation::JMPabs:	Primitive::jump_absolute(destination(), flow_controller);						return;
+		case Operation::JMPfar:	Primitive::jump_far<model>(instruction, flow_controller, registers, memory);	return;
+
+		case Operation::IRET:		Primitive::iret(registers, flow_controller, memory, status);			return;
 		case Operation::RETnear:	Primitive::ret_near(instruction, registers, flow_controller, memory);	return;
 		case Operation::RETfar:		Primitive::ret_far(instruction, registers, flow_controller, memory);	return;
 
diff --git a/OSBindings/Mac/Clock SignalTests/8088Tests.mm b/OSBindings/Mac/Clock SignalTests/8088Tests.mm
index 0f9db80f8..f4228ca3b 100644
--- a/OSBindings/Mac/Clock SignalTests/8088Tests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/8088Tests.mm	
@@ -214,20 +214,24 @@ class FlowController {
 
 		void call(uint16_t address) {
 			push(registers_.ip_);
-			registers_.ip_ = address;
+			jump(address);
 		}
 
 		void call(uint16_t segment, uint16_t offset) {
 			push(registers_.cs_);
 			push(registers_.ip_);
-			registers_.cs_ = segment;
-			registers_.ip_ = offset;
+			jump(segment, offset);
 		}
 
 		void jump(uint16_t address) {
 			registers_.ip_ = address;
 		}
 
+		void jump(uint16_t segment, uint16_t address) {
+			registers_.cs_ = segment;
+			registers_.ip_ = address;
+		}
+
 		void halt() {}
 		void wait() {}
 
@@ -365,14 +369,22 @@ struct FailedExecution {
 		// CALL
 		@"E8.json.gz",	@"FF.2.json.gz",
 		@"9A.json.gz",	@"FF.3.json.gz",
-*/
+
 		// IRET
 		@"CF.json.gz",
 
 		@"C3.json.gz",	@"C2.json.gz",	// near RET
 		@"CB.json.gz",	@"CA.json.gz",	// far RET
+*/
+		// relative JMP
+		@"EB.json.gz",		@"E9.json.gz",
+
+		// far JMP
+		@"EA.josn.gz",		@"FF.5.json.gz",
+
+		@"FF.4.json.gz",	// absolute JMP
+
 /*
-		// TODO: JMP
 		// TODO: JCXZ
 
 		// INTO