cairo_lang_lowering/add_withdraw_gas/
mod.rs

1use cairo_lang_diagnostics::Maybe;
2use cairo_lang_semantic::corelib::{
3    core_module, core_submodule, get_function_id, never_ty, option_none_variant,
4    option_some_variant, unit_ty,
5};
6use cairo_lang_semantic::items::constant::ConstValue;
7use cairo_lang_semantic::{ConcreteTypeId, GenericArgumentId, MatchArmSelector, TypeLongId};
8use cairo_lang_utils::{Intern, LookupIntern, extract_matches};
9use num_bigint::{BigInt, Sign};
10
11use crate::db::LoweringGroup;
12use crate::ids::{ConcreteFunctionWithBodyId, LocationId, SemanticFunctionIdEx};
13use crate::lower::context::{VarRequest, VariableAllocator};
14use crate::{
15    BlockId, FlatBlock, FlatBlockEnd, FlatLowered, MatchArm, MatchEnumInfo, MatchExternInfo,
16    MatchInfo, Statement, StatementCall, VarUsage,
17};
18
19/// Main function for the add_withdraw_gas lowering phase. Adds a `withdraw_gas` statement to the
20/// given function, if needed.
21pub fn add_withdraw_gas(
22    db: &dyn LoweringGroup,
23    function: ConcreteFunctionWithBodyId,
24    lowered: &mut FlatLowered,
25) -> Maybe<()> {
26    if db.needs_withdraw_gas(function)? {
27        add_withdraw_gas_to_function(db, function, lowered)?;
28    }
29
30    Ok(())
31}
32
33/// Adds a `withdraw_gas` call statement to the given function.
34/// Creates a new root block that matches on `withdraw_gas`, moves the old root block to the success
35/// arm of it, and creates a new panic block for the failure arm.
36fn add_withdraw_gas_to_function(
37    db: &dyn LoweringGroup,
38    function: ConcreteFunctionWithBodyId,
39    lowered: &mut FlatLowered,
40) -> Maybe<()> {
41    let location = LocationId::from_stable_location(db, function.stable_location(db)?)
42        .with_auto_generation_note(db, "withdraw_gas");
43    let panic_block = create_panic_block(db, function, lowered, location)?;
44
45    let old_root_block = lowered.blocks.root_block()?.clone();
46    let old_root_new_id = lowered.blocks.push(old_root_block);
47    let panic_block_id = lowered.blocks.push(panic_block);
48    let new_root_block = FlatBlock {
49        statements: vec![],
50        end: FlatBlockEnd::Match {
51            info: MatchInfo::Extern(MatchExternInfo {
52                function: get_function_id(
53                    db.upcast(),
54                    core_submodule(db.upcast(), "gas"),
55                    "withdraw_gas".into(),
56                    vec![],
57                )
58                .lowered(db),
59                inputs: vec![],
60                arms: vec![
61                    MatchArm {
62                        arm_selector: MatchArmSelector::VariantId(option_some_variant(
63                            db.upcast(),
64                            unit_ty(db.upcast()),
65                        )),
66                        block_id: old_root_new_id,
67                        var_ids: vec![],
68                    },
69                    MatchArm {
70                        arm_selector: MatchArmSelector::VariantId(option_none_variant(
71                            db.upcast(),
72                            unit_ty(db.upcast()),
73                        )),
74                        block_id: panic_block_id,
75                        var_ids: vec![],
76                    },
77                ],
78                location,
79            }),
80        },
81    };
82
83    lowered.blocks.reset_block(BlockId(0), new_root_block);
84
85    Ok(())
86}
87
88/// Creates the panic block for the case `withdraw_gas` failure.
89fn create_panic_block(
90    db: &dyn LoweringGroup,
91    function: ConcreteFunctionWithBodyId,
92    lowered: &mut FlatLowered,
93    location: LocationId,
94) -> Maybe<FlatBlock> {
95    let mut variables = VariableAllocator::new(
96        db,
97        function.function_with_body_id(db).base_semantic_function(db),
98        lowered.variables.clone(),
99    )?;
100    let never_ty = never_ty(db.upcast());
101    let never_var = variables.new_var(VarRequest { ty: never_ty, location });
102    lowered.variables = variables.variables;
103
104    let gas_panic_fn = get_function_id(
105        db.upcast(),
106        core_module(db.upcast()),
107        "panic_with_const_felt252".into(),
108        vec![GenericArgumentId::Constant(
109            ConstValue::Int(
110                BigInt::from_bytes_be(Sign::Plus, "Out of gas".as_bytes()),
111                db.core_info().felt252,
112            )
113            .intern(db),
114        )],
115    )
116    .lowered(db);
117
118    let never_enum_id = extract_matches!(
119        extract_matches!(never_ty.lookup_intern(db), TypeLongId::Concrete),
120        ConcreteTypeId::Enum
121    );
122
123    // The block consists of calling  panic_with_const_felt252::<'Out of gas'> and matching on its
124    // `never` result.
125    Ok(FlatBlock {
126        statements: vec![Statement::Call(StatementCall {
127            function: gas_panic_fn,
128            inputs: vec![],
129            with_coupon: false,
130            outputs: vec![never_var],
131            location,
132        })],
133        end: FlatBlockEnd::Match {
134            info: MatchInfo::Enum(MatchEnumInfo {
135                concrete_enum_id: never_enum_id,
136                input: VarUsage { var_id: never_var, location },
137                arms: vec![],
138                location,
139            }),
140        },
141    })
142}
cairo_lang_lowering/add_withdraw_gas/mod.rs

cairo_lang_lowering/add_withdraw_gas/
mod.rs
