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Regex: Use a template argument instead of a regular one for "forward"

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forward (which controls if we are compling for forward or backward
matching) is always statically known, and compilation will first
compile forward, then backward (if needed), so by having separate
compiled function we get rid of runtime branches.
This commit is contained in:
Maxime Coste 2018-02-09 22:35:12 +11:00
parent aa9f7753e8
commit 3584e00d19
1 changed files with 69 additions and 66 deletions
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135
src/regex_impl.cc
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@ -87,38 +87,46 @@ struct ParsedRegex
namespace
{
template<typename Func>
bool for_each_child(const ParsedRegex& parsed_regex, ParsedRegex::NodeIndex index, Func&& func)
template<MatchDirection = MatchDirection::Forward>
struct ForEachChild
{
const auto end = parsed_regex.nodes[index].children_end;
for (auto child = index+1; child != end;
child = parsed_regex.nodes[child].children_end)
template<typename Func>
static bool apply(const ParsedRegex& parsed_regex, ParsedRegex::NodeIndex index, Func&& func)
{
if (func(child) == false)
return false;
const auto end = parsed_regex.nodes[index].children_end;
for (auto child = index+1; child != end;
child = parsed_regex.nodes[child].children_end)
{
if (func(child) == false)
return false;
}
return true;
}
return true;
}
};
template<typename Func>
bool for_each_child_reverse(const ParsedRegex& parsed_regex, ParsedRegex::NodeIndex index, Func&& func)
template<>
struct ForEachChild<MatchDirection::Backward>
{
auto find_last_child = [&](ParsedRegex::NodeIndex begin, ParsedRegex::NodeIndex end) {
while (parsed_regex.nodes[begin].children_end != end)
begin = parsed_regex.nodes[begin].children_end;
return begin;
};
const auto first_child = index+1;
auto end = parsed_regex.nodes[index].children_end;
while (end != first_child)
template<typename Func>
static bool apply(const ParsedRegex& parsed_regex, ParsedRegex::NodeIndex index, Func&& func)
{
auto child = find_last_child(first_child, end);
if (func(child) == false)
return false;
end = child;
auto find_last_child = [&](ParsedRegex::NodeIndex begin, ParsedRegex::NodeIndex end) {
while (parsed_regex.nodes[begin].children_end != end)
begin = parsed_regex.nodes[begin].children_end;
return begin;
};
const auto first_child = index+1;
auto end = parsed_regex.nodes[index].children_end;
while (end != first_child)
{
auto child = find_last_child(first_child, end);
if (func(child) == false)
return false;
end = child;
}
return true;
}
return true;
}
};
}
// Recursive descent parser based on naming used in the ECMAScript
@ -573,7 +581,7 @@ private:
void validate_lookaround(NodeIndex index)
{
for_each_child(m_parsed_regex, index, [this](NodeIndex child_index) {
ForEachChild<>::apply(m_parsed_regex, index, [this](NodeIndex child_index) {
auto& child = get_node(child_index);
if (child.op != ParsedRegex::Literal and child.op != ParsedRegex::Class and
child.op != ParsedRegex::CharacterType and child.op != ParsedRegex::AnyChar)
@ -627,18 +635,18 @@ struct RegexCompiler
if (not (flags & RegexCompileFlags::NoForward))
{
m_program.forward_start_desc = compute_start_desc(true);
m_program.forward_start_desc = compute_start_desc<MatchDirection::Forward>();
write_search_prefix();
compile_node(0, true);
compile_node<MatchDirection::Forward>(0);
push_inst(CompiledRegex::Match);
}
if (flags & RegexCompileFlags::Backward)
{
m_program.first_backward_inst = m_program.instructions.size();
m_program.backward_start_desc = compute_start_desc(false);
m_program.backward_start_desc = compute_start_desc<MatchDirection::Backward>();
write_search_prefix();
compile_node(0, false);
compile_node<MatchDirection::Backward>(0);
push_inst(CompiledRegex::Match);
}
else
@ -652,7 +660,8 @@ struct RegexCompiler
private:
uint32_t compile_node_inner(ParsedRegex::NodeIndex index, bool forward)
template<MatchDirection direction>
uint32_t compile_node_inner(ParsedRegex::NodeIndex index)
{
auto& node = get_node(index);
@ -661,6 +670,7 @@ private:
const bool save = (node.op == ParsedRegex::Alternation or node.op == ParsedRegex::Sequence) and
(node.value == 0 or (node.value != -1 and not (m_flags & RegexCompileFlags::NoSubs)));
constexpr bool forward = direction == MatchDirection::Forward;
if (save)
push_inst(CompiledRegex::Save, node.value * 2 + (forward ? 0 : 1));
@ -684,28 +694,23 @@ private:
break;
case ParsedRegex::Sequence:
{
if (forward)
for_each_child(m_parsed_regex, index, [this](ParsedRegex::NodeIndex child) {
compile_node(child, true); return true;
});
else
for_each_child_reverse(m_parsed_regex, index, [this](ParsedRegex::NodeIndex child) {
compile_node(child, false); return true;
});
ForEachChild<direction>::apply(m_parsed_regex, index, [this](ParsedRegex::NodeIndex child) {
compile_node<direction>(child); return true;
});
break;
}
case ParsedRegex::Alternation:
{
auto split_pos = m_program.instructions.size();
for_each_child(m_parsed_regex, index, [this, index](ParsedRegex::NodeIndex child) {
ForEachChild<>::apply(m_parsed_regex, index, [this, index](ParsedRegex::NodeIndex child) {
if (child != index+1)
push_inst(CompiledRegex::Split_PrioritizeParent);
return true;
});
for_each_child(m_parsed_regex, index,
[&, end = node.children_end](ParsedRegex::NodeIndex child) {
auto node = compile_node(child, forward);
ForEachChild<>::apply(m_parsed_regex, index,
[&, end = node.children_end](ParsedRegex::NodeIndex child) {
auto node = compile_node<direction>(child);
if (child != index+1)
m_program.instructions[split_pos++].param = node;
if (get_node(child).children_end != end)
@ -722,28 +727,28 @@ private:
: CompiledRegex::LookAhead)
: (ignore_case ? CompiledRegex::LookBehind_IgnoreCase
: CompiledRegex::LookBehind),
push_lookaround(index, false, ignore_case));
push_lookaround<MatchDirection::Forward>(index, ignore_case));
break;
case ParsedRegex::NegativeLookAhead:
push_inst(forward ? (ignore_case ? CompiledRegex::NegativeLookAhead_IgnoreCase
: CompiledRegex::NegativeLookAhead)
: (ignore_case ? CompiledRegex::NegativeLookBehind_IgnoreCase
: CompiledRegex::NegativeLookBehind),
push_lookaround(index, false, ignore_case));
push_lookaround<MatchDirection::Forward>(index, ignore_case));
break;
case ParsedRegex::LookBehind:
push_inst(forward ? (ignore_case ? CompiledRegex::LookBehind_IgnoreCase
: CompiledRegex::LookBehind)
: (ignore_case ? CompiledRegex::LookAhead_IgnoreCase
: CompiledRegex::LookAhead),
push_lookaround(index, true, ignore_case));
push_lookaround<MatchDirection::Backward>(index, ignore_case));
break;
case ParsedRegex::NegativeLookBehind:
push_inst(forward ? (ignore_case ? CompiledRegex::NegativeLookBehind_IgnoreCase
: CompiledRegex::NegativeLookBehind)
: (ignore_case ? CompiledRegex::NegativeLookAhead_IgnoreCase
: CompiledRegex::NegativeLookAhead),
push_lookaround(index, true, ignore_case));
push_lookaround<MatchDirection::Backward>(index, ignore_case));
break;
case ParsedRegex::LineStart:
push_inst(forward ? CompiledRegex::LineStart
@ -781,7 +786,8 @@ private:
return start_pos;
}
uint32_t compile_node(ParsedRegex::NodeIndex index, bool forward)
template<MatchDirection direction>
uint32_t compile_node(ParsedRegex::NodeIndex index)
{
auto& node = get_node(index);
@ -799,10 +805,10 @@ private:
goto_ends.push_back(split_pos);
}
auto inner_pos = compile_node_inner(index, forward);
auto inner_pos = compile_node_inner<direction>(index);
// Write the node multiple times when we have a min count quantifier
for (int i = 1; i < quantifier.min; ++i)
inner_pos = compile_node_inner(index, forward);
inner_pos = compile_node_inner<direction>(index);
if (quantifier.allows_infinite_repeat())
push_inst(quantifier.greedy ? CompiledRegex::Split_PrioritizeChild
@ -816,7 +822,7 @@ private:
auto split_pos = push_inst(quantifier.greedy ? CompiledRegex::Split_PrioritizeParent
: CompiledRegex::Split_PrioritizeChild);
goto_ends.push_back(split_pos);
compile_node_inner(index, forward);
compile_node_inner<direction>(index);
}
for (auto offset : goto_ends)
@ -845,7 +851,8 @@ private:
return res;
}
uint32_t push_lookaround(ParsedRegex::NodeIndex index, bool reversed, bool ignore_case)
template<MatchDirection direction>
uint32_t push_lookaround(ParsedRegex::NodeIndex index, bool ignore_case)
{
uint32_t res = m_program.lookarounds.size();
auto write_matcher = [this, ignore_case](ParsedRegex::NodeIndex child) {
@ -864,10 +871,7 @@ private:
return true;
};
if (reversed)
for_each_child_reverse(m_parsed_regex, index, write_matcher);
else
for_each_child(m_parsed_regex, index, write_matcher);
ForEachChild<direction>::apply(m_parsed_regex, index, write_matcher);
m_program.lookarounds.push_back((Codepoint)-1);
return res;
@ -876,8 +880,9 @@ private:
// Fills accepted and rejected according to which chars can start the given node,
// returns true if the node did not consume the char, hence a following node in
// sequence would be still relevant for the parent node start chars computation.
template<MatchDirection direction>
bool compute_start_desc(ParsedRegex::NodeIndex index,
CompiledRegex::StartDesc& start_desc, bool forward) const
CompiledRegex::StartDesc& start_desc) const
{
auto& node = get_node(index);
switch (node.op)
@ -939,20 +944,17 @@ private:
{
bool did_not_consume = false;
auto does_not_consume = [&, this](auto child) {
return this->compute_start_desc(child, start_desc, forward);
return this->compute_start_desc<direction>(child, start_desc);
};
if (forward)
did_not_consume = for_each_child(m_parsed_regex, index, does_not_consume);
else
did_not_consume = for_each_child_reverse(m_parsed_regex, index, does_not_consume);
did_not_consume = ForEachChild<direction>::apply(m_parsed_regex, index, does_not_consume);
return did_not_consume or node.quantifier.allows_none();
}
case ParsedRegex::Alternation:
{
bool all_consumed = not node.quantifier.allows_none();
for_each_child(m_parsed_regex, index, [&](ParsedRegex::NodeIndex child) {
if (compute_start_desc(child, start_desc, forward))
ForEachChild<>::apply(m_parsed_regex, index, [&](ParsedRegex::NodeIndex child) {
if (compute_start_desc<direction>(child, start_desc))
all_consumed = false;
return true;
});
@ -974,11 +976,12 @@ private:
return false;
}
template<MatchDirection direction>
[[gnu::noinline]]
std::unique_ptr<CompiledRegex::StartDesc> compute_start_desc(bool forward) const
std::unique_ptr<CompiledRegex::StartDesc> compute_start_desc() const
{
CompiledRegex::StartDesc start_desc{};
if (compute_start_desc(0, start_desc, forward) or
if (compute_start_desc<direction>(0, start_desc) or
not contains(start_desc.map, false))
return nullptr;