From 02cea3047ee5691dd6511efa7344d47effefd957 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Wed, 18 Oct 2023 14:04:21 -0400
Subject: [PATCH] Implement LOOP, LOOPE, LOOPNE.

---
 .../Implementation/PerformImplementation.hpp  | 34 ++++++++++++++++---
 OSBindings/Mac/Clock SignalTests/8088Tests.mm | 34 +++++++++++++------
 2 files changed, 53 insertions(+), 15 deletions(-)

diff --git a/InstructionSets/x86/Implementation/PerformImplementation.hpp b/InstructionSets/x86/Implementation/PerformImplementation.hpp
index fdab87e8c..d75a848e0 100644
--- a/InstructionSets/x86/Implementation/PerformImplementation.hpp
+++ b/InstructionSets/x86/Implementation/PerformImplementation.hpp
@@ -674,6 +674,30 @@ void jump(bool condition, IntT displacement, RegistersT &registers, FlowControll
 	}
 }
 
+template <typename IntT, typename OffsetT, typename RegistersT, typename FlowControllerT>
+void loop(IntT &counter, OffsetT displacement, RegistersT &registers, FlowControllerT &flow_controller) {
+	--counter;
+	if(counter) {
+		flow_controller.jump(registers.ip() + displacement);
+	}
+}
+
+template <typename IntT, typename OffsetT, typename RegistersT, typename FlowControllerT>
+void loope(IntT &counter, OffsetT displacement, RegistersT &registers, Status &status, FlowControllerT &flow_controller) {
+	--counter;
+	if(counter && status.flag<Flag::Zero>()) {
+		flow_controller.jump(registers.ip() + displacement);
+	}
+}
+
+template <typename IntT, typename OffsetT, typename RegistersT, typename FlowControllerT>
+void loopne(IntT &counter, OffsetT displacement, RegistersT &registers, Status &status, FlowControllerT &flow_controller) {
+	--counter;
+	if(counter && !status.flag<Flag::Zero>()) {
+		flow_controller.jump(registers.ip() + displacement);
+	}
+}
+
 template <typename IntT>
 void dec(IntT &destination, Status &status) {
 	/*
@@ -1452,10 +1476,12 @@ template <
 		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::JCXZ:
-			// TODO: use ECX rather than CX if address size is 32-bit.
-			jcc(!registers.cx());
-		return;
+
+		// TODO: use ECX rather than CX for all of below if address size is 32-bit.
+		case Operation::JCXZ:	jcc(!registers.cx());								return;
+		case Operation::LOOP:	Primitive::loop(registers.cx(), instruction.offset(), registers, flow_controller);				return;
+		case Operation::LOOPE:	Primitive::loope(registers.cx(), instruction.offset(), registers, status, flow_controller);		return;
+		case Operation::LOOPNE:	Primitive::loopne(registers.cx(), instruction.offset(), registers, status, flow_controller);	return;
 
 		case Operation::IRET:		Primitive::iret(registers, flow_controller, memory, status);			return;
 		case Operation::RETnear:	Primitive::ret_near(instruction, registers, flow_controller, memory);	return;
diff --git a/OSBindings/Mac/Clock SignalTests/8088Tests.mm b/OSBindings/Mac/Clock SignalTests/8088Tests.mm
index 85f8da4c9..9c1d3129b 100644
--- a/OSBindings/Mac/Clock SignalTests/8088Tests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/8088Tests.mm	
@@ -73,11 +73,6 @@ struct Registers {
 	uint16_t &ds()	{	return ds_;				}
 	uint16_t &ss()	{	return ss_;				}
 
-//	uint32_t zero_ = 0;
-//	template <typename IntT> IntT &zero() {
-//		return static_cast<IntT>(zero);
-//	}
-
 	bool operator ==(const Registers &rhs) const {
 		return
 			ax_.full == rhs.ax_.full &&
@@ -380,9 +375,8 @@ struct FailedExecution {
 		@"EA.josn.gz",	@"FF.5.json.gz",	// far JMP
 
 		@"FF.4.json.gz",	// absolute JMP
-*/
 		@"E3.json.gz",		// JCXZ
-/*
+
 		// INTO
 		@"CE.json.gz",
 
@@ -397,9 +391,11 @@ struct FailedExecution {
 		@"8D.json.gz",	// LEA
 
 		// TODO: CMPS, LODS, MOVS, SCAS, STOS
-
-		// TODO: LOOP, LOOPE, LOOPNE
-
+*/
+		@"E0.json.gz",	// LOOPNE
+		@"E1.json.gz",	// LOOPE
+		@"E2.json.gz",	// LOOP
+/*
 		// MOV
 		@"88.json.gz",	@"89.json.gz",	@"8A.json.gz",	@"8B.json.gz",
 		@"8C.json.gz",	@"8E.json.gz",
@@ -717,7 +713,23 @@ struct FailedExecution {
 					difference.to_string().c_str()]];
 		}
 		if(!registersEqual) {
-			[reasons addObject:@"registers don't match"];
+			NSMutableArray<NSString *> *registers = [[NSMutableArray alloc] init];
+			if(intended_registers.ax() != execution_support.registers.ax())	[registers addObject:@"ax"];
+			if(intended_registers.cx() != execution_support.registers.cx())	[registers addObject:@"cx"];
+			if(intended_registers.dx() != execution_support.registers.dx())	[registers addObject:@"dx"];
+			if(intended_registers.bx() != execution_support.registers.bx())	[registers addObject:@"bx"];
+			if(intended_registers.sp() != execution_support.registers.sp())	[registers addObject:@"sp"];
+			if(intended_registers.bp() != execution_support.registers.bp())	[registers addObject:@"bp"];
+			if(intended_registers.si() != execution_support.registers.si())	[registers addObject:@"si"];
+			if(intended_registers.di() != execution_support.registers.di())	[registers addObject:@"di"];
+			if(intended_registers.ip() != execution_support.registers.ip())	[registers addObject:@"ip"];
+			if(intended_registers.es() != execution_support.registers.es())	[registers addObject:@"es"];
+			if(intended_registers.cs() != execution_support.registers.cs())	[registers addObject:@"cs"];
+			if(intended_registers.ds() != execution_support.registers.ds())	[registers addObject:@"ds"];
+			if(intended_registers.ss() != execution_support.registers.ss())	[registers addObject:@"ss"];
+			[reasons addObject:[NSString stringWithFormat:
+				@"registers don't match: %@", [registers componentsJoinedByString:@", "]
+			]];
 		}
 		if(!ramEqual) {
 			[reasons addObject:@"RAM contents don't match"];