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LibJS: Use a Vector<u8> for BasicBlock instruction storage

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This reduces the minimum size of a basic block from 4 KiB to 0 bytes.
With this change, memory usage at the end of Speedometer is 1.2 GiB,
down from 1.8 GiB.
This commit is contained in:
Andreas Kling 2023-09-28 09:29:42 +02:00
parent 89a86798a2
commit d24e07579f
4 changed files with 20 additions and 67 deletions
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24
Userland/Libraries/LibJS/Bytecode/BasicBlock.cpp
View file

@ -10,19 +10,14 @@
namespace JS::Bytecode {
NonnullOwnPtr<BasicBlock> BasicBlock::create(DeprecatedString name, size_t size)
NonnullOwnPtr<BasicBlock> BasicBlock::create(DeprecatedString name)
{
return adopt_own(*new BasicBlock(move(name), max(size, static_cast<size_t>(4 * KiB))));
return adopt_own(*new BasicBlock(move(name)));
}
BasicBlock::BasicBlock(DeprecatedString name, size_t size)
BasicBlock::BasicBlock(DeprecatedString name)
: m_name(move(name))
{
// FIXME: This is not the smartest solution ever. Find something cleverer!
// The main issue we're working around here is that we don't want pointers into the bytecode stream to become invalidated
// during code generation due to dynamic buffer resizing. Otherwise we could just use a Vector.
m_buffer_capacity = size;
m_buffer = new u8[m_buffer_capacity];
}
BasicBlock::~BasicBlock()
@ -33,16 +28,6 @@ BasicBlock::~BasicBlock()
++it;
Instruction::destroy(const_cast<Instruction&>(to_destroy));
}
delete[] m_buffer;
}
void BasicBlock::seal()
{
// FIXME: mprotect the instruction stream as PROT_READ
// This is currently not possible because instructions can have destructors (that clean up strings)
// Instructions should instead be destructor-less and refer to strings in a string table on the Bytecode::Block.
// It also doesn't work because instructions that have String members use RefPtr internally which must be in writable memory.
}
void BasicBlock::dump(Bytecode::Executable const& executable) const
@ -58,8 +43,7 @@ void BasicBlock::dump(Bytecode::Executable const& executable) const
void BasicBlock::grow(size_t additional_size)
{
m_buffer_size += additional_size;
VERIFY(m_buffer_size <= m_buffer_capacity);
m_buffer.resize(m_buffer.size() + additional_size);
}
}