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LibWasm: Hold on to the stack depth for expressions in the validator

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This allows preallocating the value stack when pushing frames, avoiding
repeated reallocs and copies.
This commit is contained in:
Ali Mohammad Pur 2025-06-06 14:12:28 +02:00 • committed by Ali Mohammad Pur
commit dc67f0ad4e
Notes: github-actions[bot] 2025-08-08 10:56:54 +00:00
4 changed files with 17 additions and 1 deletions
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2
Libraries/LibWasm/AbstractMachine/Configuration.h
View file

@ -21,6 +21,8 @@ public:
{
Label label(frame.arity(), frame.expression().instructions().size(), m_value_stack.size());
frame.label_index() = m_label_stack.size();
if (auto hint = frame.expression().stack_usage_hint(); hint.has_value())
m_value_stack.ensure_capacity(*hint);
m_frame_stack.append(move(frame));
m_label_stack.append(label);
}

2
Libraries/LibWasm/AbstractMachine/Validator.cpp
View file

@ -3736,6 +3736,8 @@ ErrorOr<Validator::ExpressionTypeResult, ValidationError> Validator::validate(Ex
m_frames.take_last();
VERIFY(m_frames.is_empty());
expression.set_stack_usage_hint(stack.max_known_size());
return ExpressionTypeResult { stack.release_vector(), is_constant_expression };
}

10
Libraries/LibWasm/AbstractMachine/Validator.h
View file

@ -228,6 +228,7 @@ public:
void append(StackEntry entry)
{
Vector<StackEntry>::append(entry);
m_max_known_size = max(m_max_known_size, size());
}
ErrorOr<StackEntry, ValidationError> take(ValueType type, SourceLocation location = SourceLocation::current())
@ -254,10 +255,17 @@ public:
return {};
}
Vector<StackEntry> release_vector() { return exchange(static_cast<Vector<StackEntry>&>(*this), Vector<StackEntry> {}); }
Vector<StackEntry> release_vector()
{
m_max_known_size = 0;
return exchange(static_cast<Vector<StackEntry>&>(*this), Vector<StackEntry> {});
}
size_t max_known_size() const { return m_max_known_size; }
private:
Vector<Frame> const& m_frames;
size_t m_max_known_size { 0 };
};
struct ExpressionTypeResult {

4
Libraries/LibWasm/Types.h
View file

@ -708,8 +708,12 @@ public:
static ParseResult<Expression> parse(ConstrainedStream& stream, Optional<size_t> size_hint = {});
void set_stack_usage_hint(size_t value) const { m_stack_usage_hint = value; }
auto stack_usage_hint() const { return m_stack_usage_hint; }
private:
Vector<Instruction> m_instructions;
mutable Optional<size_t> m_stack_usage_hint;
};
class GlobalSection {