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Merged
ehwan merged 17 commits into from
Sep 13, 2025
+1,855 −1,361
Merged

Single rule optimization can be applied with custom reduce action #32

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0bcfedc
fix cycle handling logic in optimize_iterate
ehwan Sep 11, 2025
dbdd434
add data for custom reduce action storage
ehwan Sep 11, 2025
652cc1e
add reduce_action_chain to TokenMapped
ehwan Sep 11, 2025
91969b1
emit custom single reduce action
ehwan Sep 12, 2025
c9aa52a
move rule.is_used filter from emit
ehwan Sep 12, 2025
fac5d95
WIP
ehwan Sep 12, 2025
536b38b
Merge branch 'main' into custom_reduceaction_optimize
ehwan Sep 13, 2025
ac371bd
emit.rs from main
ehwan Sep 13, 2025
8465698
no optimize if action contains lookahead
ehwan Sep 13, 2025
26ae58b
emit custom single reduce action
ehwan Sep 13, 2025
bbf74d0
fix bootstrap test runs diff test first
ehwan Sep 13, 2025
b64d1ce
emit for custom reduce action
ehwan Sep 13, 2025
6ef9db1
fix optimize end condition
ehwan Sep 13, 2025
972e488
fix calculator example
ehwan Sep 13, 2025
bf36016
remove unnecessary location clone
ehwan Sep 13, 2025
a283593
fix optimize count for derive
ehwan Sep 13, 2025
fd983e0
fix optimize iteration terminate logic
ehwan Sep 13, 2025
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5 changes: 4 additions & 1 deletion example/calculator/src/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -61,10 +61,13 @@ A(i32) : A plus a2=A {
| M
;

M(i32) : M star m2=M { M * m2 }
M(i32) : M_optim star m2=M_optim { M_optim * m2 }
| P
;

// check for single-rule optimization
M_optim(i32): M { M * 1 };

P(i32) : num {
if let Token::Num(n) = num { n }
else { return Err(format!("{:?}", num)); }
Expand Down
2 changes: 1 addition & 1 deletion rusty_lr_buildscript/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -761,7 +761,7 @@ impl Builder {
// diagnostics for optimization
if grammar.optimize {
use rusty_lr_parser::grammar::OptimizeRemove;
let optimized = grammar.optimize(10);
let optimized = grammar.optimize(25);

if self.note_optimization {
// terminals merged into terminal class
Expand Down
2 changes: 1 addition & 1 deletion rusty_lr_derive/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ pub fn lr1(input: TokenStream) -> TokenStream {
Err(e) => return e.to_compile_error().into(),
};
if grammar.optimize {
grammar.optimize(5);
grammar.optimize(15);
}
grammar.builder = grammar.create_builder();
let diags = grammar.build_grammar();
Expand Down
204 changes: 174 additions & 30 deletions rusty_lr_parser/src/emit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1102,6 +1102,45 @@ impl Grammar {
// TokenStream to define reduce function for each production rule
let mut fn_reduce_for_each_rule_stream = TokenStream::new();

for (i, action) in self.custom_reduce_actions.iter().enumerate() {
let fn_name = format_ident!("custom_reduce_action_{}", i);

let data_arg = action
.input_type
.as_ref()
.map(|(name, ty)| {
quote! { mut #name: #ty, }
})
.unwrap_or_default();

let location_arg = action
.input_location
.as_ref()
.map(|name| {
quote! { mut #name: #location_typename, }
})
.unwrap_or_default();

let body = &action.body.body;

let output_type = if let Some(ty) = action.output_type.as_ref() {
ty.clone()
} else {
quote! { () }
};

fn_reduce_for_each_rule_stream.extend(quote! {
fn #fn_name(
#data_arg
#location_arg
#user_data_parameter_name: &mut #user_data_typename,
__rustylr_location0: &mut #location_typename,
) -> Result<#output_type, #reduce_error_typename> {
Ok(#body)
}
});
}

let mut rule_index: usize = 0;
for (nonterm_idx, nonterm) in self.nonterminals.iter().enumerate() {
for (rule_local_id, rule) in nonterm.rules.iter().enumerate() {
Expand Down Expand Up @@ -1129,9 +1168,8 @@ impl Grammar {
if rule.is_used {
let mut debug_tag_check_stream = TokenStream::new();
let mut stack_mapto_map = std::collections::BTreeMap::new();
for (token_index_from_end, token) in
rule.tokens.iter().rev().enumerate()
{
for (token_idx, token) in rule.tokens.iter().enumerate().rev() {
let token_index_from_end = rule.tokens.len() - 1 - token_idx;
let stack_name = token_to_stack_name(token.token);
let tag_name = stack_name.unwrap_or(&empty_tag_name);

Expand All @@ -1152,59 +1190,82 @@ impl Grammar {
}

if let Some(stack_name) = stack_name {
// if variable was not used at this reduce action,
// we can use `truncate` instead of `pop` for optimization
// so check it here
let mapto = if let Some(mapto) = &token.mapto {
if reduce_action.contains_ident(mapto) {
Some(mapto.clone())
let mapto = if let Some(first_chain) =
token.reduce_action_chains.first()
{
let first_chain = &self.custom_reduce_actions[*first_chain];
if first_chain.input_type.is_some() {
Some(format_ident!("__rustylr_data_{}", token_idx))
} else {
None
}
} else {
None
// if variable was not used at this reduce action,
// we can use `truncate` instead of `pop` for optimization
// so check it here
if let Some(mapto) = &token.mapto {
if reduce_action.contains_ident(mapto) {
Some(mapto.clone())
} else {
None
}
} else {
None
}
};
stack_mapto_map
.entry(StackName::DataStack(stack_name.clone()))
.or_insert_with(Vec::new)
.push(mapto);
}
let location_mapto = if let Some(mapto) = &token.mapto {
let location_varname =
format_ident!("__rustylr_location_{}", mapto);

// if variable was not used at this reduce action,
// we can use `truncate` instead of `pop` for optimization
// so check it here
if reduce_action.contains_ident(&location_varname) {
Some(location_varname)
let location_mapto = if token.reduce_action_chains.is_empty() {
if let Some(mapto) = &token.mapto {
let location_varname =
format_ident!("__rustylr_location_{}", mapto);

// if variable was not used at this reduce action,
// we can use `truncate` instead of `pop` for optimization
// so check it here
if reduce_action.contains_ident(&location_varname) {
Some(location_varname)
} else {
None
}
} else {
None
}
} else {
None
if token.reduce_action_chains.iter().any(|&idx| {
let action = &self.custom_reduce_actions[idx];
action.input_location.is_some()
}) {
Some(format_ident!("__rustylr_location_{}", token_idx))
} else {
None
}
};
stack_mapto_map
.entry(StackName::LocationStack)
.or_insert_with(Vec::new)
.push(location_mapto);

debug_tag_check_stream.extend(quote! {
debug_assert!(
__data_stack.#tag_stack_name.get(
__data_stack.#tag_stack_name.len()-1-#token_index_from_end
) == Some( &#tag_enum_name::#tag_name )
);
});
debug_assert!(
__data_stack.#tag_stack_name.get(
__data_stack.#tag_stack_name.len()-1-#token_index_from_end
) == Some( &#tag_enum_name::#tag_name )
);
});
}

// if there are variable with same name, the last one will be used (by shadowing)
// so set the front one to `None`
// this will also help optimizing performance by using `truncate` instead of `pop`
for maptos in &mut stack_mapto_map.values_mut() {
for var_right in (0..maptos.len()).rev() {
// maptos is in reverse order of the rule tokens
for var_right in 0..maptos.len() {
if let Some(var_name) = maptos[var_right].as_ref().cloned() {
for var_left in 0..var_right {
for var_left in var_right + 1..maptos.len() {
if maptos[var_left].as_ref() == Some(&var_name) {
maptos[var_left] = None;
Comment on lines +1266 to 1270

Copilot AI Sep 13, 2025

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[nitpick] The variable names var_right and var_left are misleading since the loop direction has changed. With the comment indicating reverse order and the loops now going forward, these names create confusion about the actual iteration direction.

Copilot uses AI. Check for mistakes.
}
Expand Down Expand Up @@ -1273,8 +1334,89 @@ impl Grammar {
}
if last_none_count > 0 {
extract_data_stream.extend(quote! {
#stack_stream.truncate(#stack_stream.len() - #last_none_count);
});
#stack_stream.truncate(#stack_stream.len() - #last_none_count);
});
}
}

let mut custom_reduce_action_stream = TokenStream::new();
for (token_idx, token) in rule.tokens.iter().enumerate() {
if token.reduce_action_chains.is_empty() {
continue;
}
let data_varname = format_ident!("__rustylr_data_{}", token_idx);
let location_varname =
format_ident!("__rustylr_location_{}", token_idx);
let location_used_in_this_action = if let Some(mapto) = &token.mapto
{
let location_mapto_varname =
format_ident!("__rustylr_location_{}", mapto);
reduce_action.contains_ident(&location_mapto_varname)
} else {
false
};

for (idx, &chain_idx) in
token.reduce_action_chains.iter().enumerate()
{
let action = &self.custom_reduce_actions[chain_idx];
let fn_name =
format_ident!("custom_reduce_action_{}", chain_idx);

let data_arg = if action.input_type.is_some() {
quote! { #data_varname, }
} else {
quote! {}
};

// if location is needed for later reduce action, pass by clone
// else, pass by move
let mut location_used_later = location_used_in_this_action;
if !location_used_later {
for &chain_idx in
token.reduce_action_chains[idx + 1..].iter()
{
let action = &self.custom_reduce_actions[chain_idx];
if action.input_location.is_some() {
location_used_later = true;
break;
}
}
}
let location_arg = if action.input_location.is_some() {
if location_used_later {
quote! { #location_varname.clone(), }
} else {
quote! { #location_varname, }
}
} else {
quote! {}
};

custom_reduce_action_stream.extend(quote! {
let #data_varname = Self::#fn_name(
#data_arg
#location_arg
#user_data_parameter_name,
__rustylr_location0,
)?;
});
}

if let Some(mapto) = &token.mapto {
if reduce_action.contains_ident(mapto) {
custom_reduce_action_stream.extend(quote! {
let mut #mapto = #data_varname;
});
}
let location_mapto_varname =
format_ident!("__rustylr_location_{}", mapto);

if reduce_action.contains_ident(&location_mapto_varname) {
custom_reduce_action_stream.extend(quote! {
let mut #location_mapto_varname = #location_varname;
});
}
}
}

Expand Down Expand Up @@ -1305,6 +1447,7 @@ impl Grammar {
#modify_tag_stream

#extract_data_stream
#custom_reduce_action_stream

let __res = #body;
__data_stack.#stack_name.push(__res);
Expand Down Expand Up @@ -1332,6 +1475,7 @@ impl Grammar {
#modify_tag_stream

#extract_data_stream
#custom_reduce_action_stream

#body

Expand Down
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