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LibWasm: Avoid memory copy in read_value<T>() if possible

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If the address is already aligned properly, just read a T from it;
otherwise copy it to a local aligned array. This was a bottleneck on
memory-heavy benchmarks.
This commit is contained in:
Ali Mohammad Pur 2025-06-06 14:07:22 +02:00 • committed by Ali Mohammad Pur
commit bd7c188b86
Notes: github-actions[bot] 2025-08-08 10:57:15 +00:00
1 changed files with 8 additions and 18 deletions
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26
Libraries/LibWasm/AbstractMachine/BytecodeInterpreter.cpp
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@ -370,35 +370,25 @@ void BytecodeInterpreter::store_to_memory(Configuration& configuration, Instruct
template<typename T>
T BytecodeInterpreter::read_value(ReadonlyBytes data)
{
FixedMemoryStream stream { data };
auto value_or_error = stream.read_value<LittleEndian<T>>();
if (value_or_error.is_error()) {
dbgln("Read from {} failed", data.data());
m_trap = Trap::from_string("Read from memory failed");
VERIFY(sizeof(T) <= data.size());
if (bit_cast<FlatPtr>(data.data()) % alignof(T)) {
alignas(T) u8 buf[sizeof(T)];
memcpy(buf, data.data(), sizeof(T));
return bit_cast<LittleEndian<T>>(buf);
}
return value_or_error.release_value();
return *bit_cast<LittleEndian<T> const*>(data.data());
}
template<>
float BytecodeInterpreter::read_value<float>(ReadonlyBytes data)
{
FixedMemoryStream stream { data };
auto raw_value_or_error = stream.read_value<LittleEndian<u32>>();
if (raw_value_or_error.is_error())
m_trap = Trap::from_string("Read from memory failed");
auto raw_value = raw_value_or_error.release_value();
return bit_cast<float>(static_cast<u32>(raw_value));
return bit_cast<float>(read_value<u32>(data));
}
template<>
double BytecodeInterpreter::read_value<double>(ReadonlyBytes data)
{
FixedMemoryStream stream { data };
auto raw_value_or_error = stream.read_value<LittleEndian<u64>>();
if (raw_value_or_error.is_error())
m_trap = Trap::from_string("Read from memory failed");
auto raw_value = raw_value_or_error.release_value();
return bit_cast<double>(static_cast<u64>(raw_value));
return bit_cast<double>(read_value<u64>(data));
}
ALWAYS_INLINE void BytecodeInterpreter::interpret_instruction(Configuration& configuration, InstructionPointer& ip, Instruction const& instruction)