From 08867f497019c39974e214f7e9450f3d828c1522 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 10 Oct 2023 22:15:33 -0400
Subject: [PATCH] Implement CMP.

---
 .../Implementation/PerformImplementation.hpp    | 17 +++++++++++------
 OSBindings/Mac/Clock SignalTests/8088Tests.mm   | 15 ++++++++++-----
 2 files changed, 21 insertions(+), 11 deletions(-)

diff --git a/InstructionSets/x86/Implementation/PerformImplementation.hpp b/InstructionSets/x86/Implementation/PerformImplementation.hpp
index 55f5582b5..8cedf3767 100644
--- a/InstructionSets/x86/Implementation/PerformImplementation.hpp
+++ b/InstructionSets/x86/Implementation/PerformImplementation.hpp
@@ -455,7 +455,7 @@ void sbb(IntT &destination, IntT source, Status &status) {
 	destination = result;
 }
 
-template <typename IntT>
+template <bool write_back, typename IntT>
 void sub(IntT &destination, IntT source, Status &status) {
 	/*
 		DEST ← DEST - SRC;
@@ -471,7 +471,9 @@ void sub(IntT &destination, IntT source, Status &status) {
 	status.zero = status.parity = result;
 	status.overflow = overflow<false, IntT>(destination, source, result);
 
-	destination = result;
+	if constexpr (write_back) {
+		destination = result;
+	}
 }
 
 template <typename IntT>
@@ -931,10 +933,13 @@ template <
 		case Operation::HLT:	flow_controller.halt();		return;
 		case Operation::WAIT:	flow_controller.wait();		return;
 
-		case Operation::ADC:	Primitive::adc(destination(), source(), status);		break;
-		case Operation::ADD:	Primitive::add(destination(), source(), status);		break;
-		case Operation::SBB:	Primitive::sbb(destination(), source(), status);		break;
-		case Operation::SUB:	Primitive::sub(destination(), source(), status);		break;
+		case Operation::ADC:	Primitive::adc(destination(), source(), status);			break;
+		case Operation::ADD:	Primitive::add(destination(), source(), status);			break;
+		case Operation::SBB:	Primitive::sbb(destination(), source(), status);			break;
+		case Operation::SUB:	Primitive::sub<true>(destination(), source(), status);		break;
+		case Operation::CMP:	Primitive::sub<false>(destination(), source(), status);		break;
+
+		// TODO: all the below could call a common registers getter?
 		case Operation::MUL:
 			if constexpr (data_size == DataSize::Byte) {
 				Primitive::mul(registers.ah(), registers.al(), source(), status);
diff --git a/OSBindings/Mac/Clock SignalTests/8088Tests.mm b/OSBindings/Mac/Clock SignalTests/8088Tests.mm
index a14a11adb..095bb4dbf 100644
--- a/OSBindings/Mac/Clock SignalTests/8088Tests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/8088Tests.mm	
@@ -390,11 +390,11 @@ struct FailedExecution {
 		@"80.6.json.gz", @"81.6.json.gz", @"83.6.json.gz",
 */
 
-		// NEG
-		@"F6.3.json.gz",	@"F7.3.json.gz",
-
-		// NOT
-		@"F6.2.json.gz",	@"F7.2.json.gz",
+//		// NEG
+//		@"F6.3.json.gz",	@"F7.3.json.gz",
+//
+//		// NOT
+//		@"F6.2.json.gz",	@"F7.2.json.gz",
 
 /*
 		// NOP
@@ -412,6 +412,11 @@ struct FailedExecution {
 		@"F5.json.gz",	// CMC
 */
 
+		// CMP
+		@"38.json.gz",	@"39.json.gz",	@"3A.json.gz",
+		@"3B.json.gz",	@"3C.json.gz",	@"3D.json.gz",
+		@"80.7.json.gz",	@"81.7.json.gz",	@"83.7.json.gz",
+
 		// TODO: CMP, TEST
 		// TODO: XCHG, XLAT
 		// TODO: SALC, SETMO, SETMOC