From 21278d028c823926ab60109b5b443d46d243660f Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 10 Mar 2024 21:56:19 -0400
Subject: [PATCH] Correct unaligned accesses.

---
 Machines/Acorn/Archimedes/Archimedes.cpp            | 10 ++++++++++
 OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/Machines/Acorn/Archimedes/Archimedes.cpp b/Machines/Acorn/Archimedes/Archimedes.cpp
index 5b976baa5..3535853d2 100644
--- a/Machines/Acorn/Archimedes/Archimedes.cpp
+++ b/Machines/Acorn/Archimedes/Archimedes.cpp
@@ -290,6 +290,10 @@ struct Memory {
 	bool write(uint32_t address, IntT source, InstructionSet::ARM::Mode mode, bool trans) {
 		(void)trans;
 
+		if constexpr (std::is_same_v<IntT, uint32_t>) {
+			address &= static_cast<uint32_t>(~3);
+		}
+
 //		if(address == 0x0200002c && address < 0x04000000) {
 //		if(address == 0x02000074) {
 //			printf("%08x <- %08x\n", address, source);
@@ -363,6 +367,12 @@ struct Memory {
 
 	template <typename IntT>
 	bool read(uint32_t address, IntT &source, InstructionSet::ARM::Mode mode, bool trans) {
+		// Unaligned addresses are presented on the bus, but in an Archimedes
+		// the bus will ignore the low two bits.
+		if constexpr (std::is_same_v<IntT, uint32_t>) {
+			address &= static_cast<uint32_t>(~3);
+		}
+
 		(void)trans;
 //		logger.info().append("R %08x", address);
 
diff --git a/OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm b/OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm
index a78530b97..0b6960de6 100644
--- a/OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm	
+++ b/OSBindings/Mac/Clock SignalTests/ARMDecoderTests.mm	
@@ -65,6 +65,9 @@ struct Memory {
 struct MemoryLedger {
 	template <typename IntT>
 	bool write(uint32_t address, IntT source, Mode, bool) {
+		if constexpr (std::is_same_v<IntT, uint32_t>) {
+			address &= static_cast<uint32_t>(~3);
+		}
 		if(write_pointer == writes.size() || writes[write_pointer].size != sizeof(IntT) || writes[write_pointer].address != address || writes[write_pointer].value != source) {
 			return false;
 		}
@@ -74,6 +77,10 @@ struct MemoryLedger {
 
 	template <typename IntT>
 	bool read(uint32_t address, IntT &source, Mode, bool) {
+		if constexpr (std::is_same_v<IntT, uint32_t>) {
+			address &= static_cast<uint32_t>(~3);
+		}
+
 		if(read_pointer == reads.size() || reads[read_pointer].size != sizeof(IntT) || reads[read_pointer].address != address) {
 			return false;
 		}