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Attempt to avoid type punning.

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This commit is contained in:
Thomas Harte
2025-04-06 22:48:22 -04:00
parent c61a9e47b2
commit fa58cc05f3
1 changed files with 29 additions and 16 deletions
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Machines/PCCompatible/LinearMemory.hpp
+29 -16
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@@ -93,7 +93,7 @@ struct SplitHolder {
// Seed value only if this is a modify
if constexpr (type == AccessType::ReadModifyWrite) {
auto buffer = reinterpret_cast<uint8_t *>(&write_back_value_);
auto buffer = reinterpret_cast<uint8_t *>(write_back_value<IntT>());
if constexpr (std::is_same_v<IntT, uint16_t>) {
buffer[0] = memory[address];
buffer[1] = memory[base];
@@ -103,7 +103,7 @@ struct SplitHolder {
}
}
return *reinterpret_cast<IntT *>(&write_back_value_);
return *write_back_value<IntT>();
}
template <typename IntT>
@@ -116,7 +116,7 @@ struct SplitHolder {
return;
}
auto buffer = reinterpret_cast<uint8_t *>(&write_back_value_);
auto buffer = reinterpret_cast<const uint8_t *>(write_back_value<IntT>());
if constexpr (std::is_same_v<IntT, uint16_t>) {
memory[write_back_address_[0]] = buffer[0];
memory[write_back_address_[1]] = buffer[1];
@@ -131,7 +131,18 @@ private:
static constexpr uint32_t NoWriteBack = 0; // A low byte address of 0 can't require write-back.
uint32_t write_back_address_[2] = {NoWriteBack, NoWriteBack};
uint32_t write_back_lead_size_;
uint32_t write_back_value_;
union {
uint16_t word;
uint32_t dword;
} write_back_value_;
template <typename IntT> IntT *write_back_value() {
static_assert(std::is_same_v<IntT, uint16_t> || std::is_same_v<IntT, uint32_t>);
if constexpr (std::is_same_v<IntT, uint16_t>) {
return &write_back_value_.word;
} else {
return &write_back_value_.dword;
}
}
};
@@ -149,19 +160,19 @@ struct LinearMemory<model, std::enable_if_t<model <= InstructionSet::x86::Model:
// Bytes: always safe.
if constexpr (std::is_same_v<IntT, uint8_t>) {
return memory[address];
}
// Split on end of address space.
if(address == MaxAddress - 1) {
return SplitHolder::access<IntT, type>(address, base, 1, memory.data());
}
// Split on end of segment if this is an 8086.
if constexpr (model == InstructionSet::x86::Model::i8086) {
const uint32_t offset = address - base;
if(offset == 0xffff) {
} else {
// Split on end of address space.
if(address == MaxAddress - 1) {
return SplitHolder::access<IntT, type>(address, base, 1, memory.data());
}
// Split on end of segment if this is an 8086.
if constexpr (model == InstructionSet::x86::Model::i8086) {
const uint32_t offset = address - base;
if(offset == 0xffff) {
return SplitHolder::access<IntT, type>(address, base, 1, memory.data());
}
}
}
// Don't split.
@@ -170,7 +181,9 @@ struct LinearMemory<model, std::enable_if_t<model <= InstructionSet::x86::Model:
template <typename IntT>
void write_back() {
SplitHolder::write_back<IntT>(memory.data());
if constexpr (!std::is_same_v<IntT, uint8_t>) {
SplitHolder::write_back<IntT>(memory.data());
}
}
template <typename IntT>