From 16e827bb2ceb6ee96b61261c6f583d3fe4121564 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 26 Feb 2024 21:27:58 -0500
Subject: [PATCH] Add basic arithmetics.

---
 InstructionSets/ARM/OperationMapper.hpp       | 12 ++++
 InstructionSets/ARM/Status.hpp                |  7 +++
 .../Mac/Clock SignalTests/ARMDecoderTests.mm  | 57 ++++++++++++++++++-
 3 files changed, 74 insertions(+), 2 deletions(-)

diff --git a/InstructionSets/ARM/OperationMapper.hpp b/InstructionSets/ARM/OperationMapper.hpp
index 85fbfae2d..a3adbc0e2 100644
--- a/InstructionSets/ARM/OperationMapper.hpp
+++ b/InstructionSets/ARM/OperationMapper.hpp
@@ -51,6 +51,18 @@ constexpr bool is_logical(DataProcessingOperation operation) {
 	}
 }
 
+constexpr bool is_comparison(DataProcessingOperation operation) {
+	switch(operation) {
+		case DataProcessingOperation::TST:
+		case DataProcessingOperation::TEQ:
+		case DataProcessingOperation::CMP:
+		case DataProcessingOperation::CMN:
+			return true;
+
+		default: return false;
+	}
+}
+
 enum class Operation {
 	MUL,	/// Rd = Rm * Rs
 	MLA,	/// Rd = Rm * Rs + Rn
diff --git a/InstructionSets/ARM/Status.hpp b/InstructionSets/ARM/Status.hpp
index 3cf3cba60..de320232d 100644
--- a/InstructionSets/ARM/Status.hpp
+++ b/InstructionSets/ARM/Status.hpp
@@ -10,6 +10,8 @@
 
 #include "OperationMapper.hpp"
 
+#include <cstdint>
+
 namespace InstructionSet::ARM {
 
 namespace ConditionCode {
@@ -45,6 +47,11 @@ struct Status {
 			carry_flag_ = value;
 		}
 
+		/// @returns @c 1 if carry is set; @c 0 otherwise.
+		uint32_t c() const {
+			return carry_flag_ ? 1 : 0;
+		}
+
 		/// Sets V if the highest bit of @c value is set; resets it otherwise.
 		void set_v(uint32_t value) {
 			overflow_flag_ = value;
diff --git a/OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm b/OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm
index d5bf8dc34..088fe37be 100644
--- a/OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm	
@@ -10,6 +10,7 @@
 
 #include "../../../InstructionSets/ARM/OperationMapper.hpp"
 #include "../../../InstructionSets/ARM/Status.hpp"
+#include "../../../Numeric/Carry.hpp"
 
 using namespace InstructionSet::ARM;
 
@@ -64,7 +65,7 @@ struct Scheduler {
 
 		constexpr DataProcessingFlags flags(f);
 		auto &destination = registers_[fields.destination()];
-		const auto &operand1 = registers_[fields.operand1()];
+		const uint32_t operand1 = registers_[fields.operand1()];
 		uint32_t operand2;
 		uint32_t rotate_carry = 0;
 
@@ -104,7 +105,59 @@ struct Scheduler {
 			case DataProcessingOperation::TST:	conditions = operand1 & operand2;	break;
 			case DataProcessingOperation::TEQ:	conditions = operand1 ^ operand2;	break;
 
-			default: break;	// ETC.
+			case DataProcessingOperation::ADD:
+			case DataProcessingOperation::ADC:
+			case DataProcessingOperation::CMN:
+				conditions = operand1 + operand2;
+
+				if constexpr (flags.operation() == DataProcessingOperation::ADC) {
+					conditions += status.c();
+				}
+
+				if constexpr (flags.set_condition_codes()) {
+					status.set_c(Numeric::carried_out<true, 31>(operand1, operand2, conditions));
+					status.set_v(Numeric::overflow<true>(operand1, operand2, conditions));
+				}
+
+				if constexpr (!is_comparison(flags.operation())) {
+					destination = conditions;
+				}
+			break;
+
+			case DataProcessingOperation::SUB:
+			case DataProcessingOperation::SBC:
+			case DataProcessingOperation::CMP:
+				conditions = operand1 - operand2;
+
+				if constexpr (flags.operation() == DataProcessingOperation::SBC) {
+					conditions -= status.c();
+				}
+
+				if constexpr (flags.set_condition_codes()) {
+					status.set_c(Numeric::carried_out<false, 31>(operand1, operand2, conditions));
+					status.set_v(Numeric::overflow<false>(operand1, operand2, conditions));
+				}
+
+				if constexpr (!is_comparison(flags.operation())) {
+					destination = conditions;
+				}
+			break;
+
+			case DataProcessingOperation::RSB:
+			case DataProcessingOperation::RSC:
+				conditions = operand2 - operand1;
+
+				if constexpr (flags.operation() == DataProcessingOperation::RSC) {
+					conditions -= status.c();
+				}
+
+				if constexpr (flags.set_condition_codes()) {
+					status.set_c(Numeric::carried_out<false, 31>(operand2, operand1, conditions));
+					status.set_v(Numeric::overflow<false>(operand2, operand1, conditions));
+				}
+
+				destination = conditions;
+			break;
 		}
 
 		// Set N and Z in a unified way.