Added const-folding 0 index access. (#6818)

crates/cairo-lang-lowering/src/ids.rs

@@ -340,10 +340,18 @@ impl FunctionId {
     pub fn semantic_full_path(&self, db: &dyn LoweringGroup) -> String {
         self.lookup_intern(db).semantic_full_path(db)
     }
-    pub fn get_extern(&self, db: &dyn LoweringGroup) -> Option<ExternFunctionId> {
+    /// Returns the function as an `ExternFunctionId` and its generic arguments, if it is an
+    /// `extern` functions.
+    pub fn get_extern(
+        &self,
+        db: &dyn LoweringGroup,
+    ) -> Option<(ExternFunctionId, Vec<GenericArgumentId>)> {
         let semantic = try_extract_matches!(self.lookup_intern(db), FunctionLongId::Semantic)?;
-        let generic = semantic.get_concrete(db.upcast()).generic_function;
-        try_extract_matches!(generic, GenericFunctionId::Extern)
+        let concrete = semantic.get_concrete(db.upcast());
+        Some((
+            try_extract_matches!(concrete.generic_function, GenericFunctionId::Extern)?,
+            concrete.generic_args,
+        ))
     }
 }
 pub trait SemanticFunctionIdEx {

crates/cairo-lang-lowering/src/optimizations/const_folding.rs

@@ -232,7 +232,7 @@ impl ConstFoldingContext<'_> {
         stmt: &mut StatementCall,
         additional_consts: &mut Vec<StatementConst>,
     ) -> Option<StatementConst> {
-        let id = stmt.function.get_extern(self.db)?;
+        let (id, _generic_args) = stmt.function.get_extern(self.db)?;
         if id == self.felt_sub {
             // (a - 0) can be replaced by a.
             let val = self.as_int(stmt.inputs[1].var_id)?;
@@ -331,7 +331,7 @@ impl ConstFoldingContext<'_> {
         &mut self,
         info: &mut MatchExternInfo,
     ) -> Option<(Option<StatementConst>, FlatBlockEnd)> {
-        let id = info.function.get_extern(self.db)?;
+        let (id, generic_args) = info.function.get_extern(self.db)?;
         if self.nz_fns.contains(&id) {
             let val = self.as_const(info.inputs[0].var_id)?;
             let is_zero = match val {
@@ -461,9 +461,7 @@ impl ConstFoldingContext<'_> {
         } else if id == self.bounded_int_constrain {
             let input_var = info.inputs[0].var_id;
             let (value, nz_ty) = self.as_int_ex(input_var)?;
-            let semantic_id =
-                extract_matches!(info.function.lookup_intern(self.db), FunctionLongId::Semantic);
-            let generic_arg = semantic_id.get_concrete(self.db.upcast()).generic_args[1];
+            let generic_arg = generic_args[1];
             let constrain_value = extract_matches!(generic_arg, GenericArgumentId::Constant)
                 .lookup_intern(self.db)
                 .into_int()
@@ -474,6 +472,20 @@ impl ConstFoldingContext<'_> {
                 Some(self.propagate_const_and_get_statement(value.clone(), output, nz_ty)),
                 FlatBlockEnd::Goto(info.arms[arm_idx].block_id, Default::default()),
             ))
+        } else if id == self.array_get {
+            if self.as_int(info.inputs[1].var_id)?.is_zero() {
+                if let [success, failure] = info.arms.as_mut_slice() {
+                    let arr = info.inputs[0].var_id;
+                    let unused_arr_output0 = self.variables.alloc(self.variables[arr].clone());
+                    let unused_arr_output1 = self.variables.alloc(self.variables[arr].clone());
+                    info.inputs.truncate(1);
+                    info.function = ModuleHelper { db: self.db, id: self.array_module }
+                        .function_id("array_snapshot_pop_front", generic_args);
+                    success.var_ids.insert(0, unused_arr_output0);
+                    failure.var_ids.insert(0, unused_arr_output1);
+                }
+            }
+            None
         } else {
             None
         }
@@ -584,8 +596,6 @@ pub struct ConstFoldingLibfuncInfo {
     upcast: ExternFunctionId,
     /// The `downcast` libfunc.
     downcast: ExternFunctionId,
-    /// The `storage_base_address_from_felt252` libfunc.
-    storage_base_address_from_felt252: ExternFunctionId,
     /// The set of functions that check if a number is zero.
     nz_fns: OrderedHashSet<ExternFunctionId>,
     /// The set of functions that check if numbers are equal.
@@ -610,8 +620,14 @@ pub struct ConstFoldingLibfuncInfo {
     bounded_int_sub: ExternFunctionId,
     /// The `bounded_int_constrain` libfunc.
     bounded_int_constrain: ExternFunctionId,
+    /// The array module.
+    array_module: ModuleId,
+    /// The `array_get` libfunc.
+    array_get: ExternFunctionId,
     /// The storage access module.
     storage_access_module: ModuleId,
+    /// The `storage_base_address_from_felt252` libfunc.
+    storage_base_address_from_felt252: ExternFunctionId,
     /// Type ranges.
     type_value_ranges: OrderedHashMap<TypeId, TypeInfo>,
 }
@@ -625,6 +641,8 @@ impl ConstFoldingLibfuncInfo {
         let bounded_int_module = core.submodule("internal").submodule("bounded_int");
         let upcast = integer_module.extern_function_id("upcast");
         let downcast = integer_module.extern_function_id("downcast");
+        let array_module = core.submodule("array");
+        let array_get = array_module.extern_function_id("array_get");
         let starknet_module = core.submodule("starknet");
         let storage_access_module = starknet_module.submodule("storage_access");
         let storage_base_address_from_felt252 =
@@ -699,7 +717,6 @@ impl ConstFoldingLibfuncInfo {
             into_box,
             upcast,
             downcast,
-            storage_base_address_from_felt252,
             nz_fns,
             eq_fns,
             uadd_fns,
@@ -712,7 +729,10 @@ impl ConstFoldingLibfuncInfo {
             bounded_int_add,
             bounded_int_sub,
             bounded_int_constrain,
+            array_module: array_module.id,
+            array_get,
             storage_access_module: storage_access_module.id,
+            storage_base_address_from_felt252,
             type_value_ranges,
         }
     }

crates/cairo-lang-lowering/src/optimizations/test_data/const_folding

@@ -4449,3 +4449,82 @@ End:
   Return(v10)
 
 //! > lowering_diagnostics
+
+//! > ==========================================================================
+
+//! > Array get at known index 0.
+
+//! > test_runner_name
+test_match_optimizer
+
+//! > function
+fn foo(x: @Array<u8>) -> Option<Box<@u8>> {
+    x.get(0)
+}
+
+//! > function_name
+foo
+
+//! > module_code
+
+//! > semantic_diagnostics
+
+//! > before
+Parameters: v0: @core::array::Array::<core::integer::u8>
+blk0 (root):
+Statements:
+  (v1: core::integer::u32) <- 0
+End:
+  Match(match core::array::array_get::<core::integer::u8>(v0, v1) {
+    Option::Some(v2) => blk1,
+    Option::None => blk2,
+  })
+
+blk1:
+Statements:
+  (v3: core::option::Option::<core::box::Box::<@core::integer::u8>>) <- Option::Some(v2)
+End:
+  Goto(blk3, {v3 -> v4})
+
+blk2:
+Statements:
+  (v5: ()) <- struct_construct()
+  (v6: core::option::Option::<core::box::Box::<@core::integer::u8>>) <- Option::None(v5)
+End:
+  Goto(blk3, {v6 -> v4})
+
+blk3:
+Statements:
+End:
+  Return(v4)
+
+//! > after
+Parameters: v0: @core::array::Array::<core::integer::u8>
+blk0 (root):
+Statements:
+  (v1: core::integer::u32) <- 0
+End:
+  Match(match core::array::array_snapshot_pop_front::<core::integer::u8>(v0) {
+    Option::Some(v7, v2) => blk1,
+    Option::None(v8) => blk2,
+  })
+
+blk1:
+Statements:
+  (v3: core::option::Option::<core::box::Box::<@core::integer::u8>>) <- Option::Some(v2)
+End:
+  Goto(blk3, {v3 -> v4})
+
+blk2:
+Statements:
+  (v5: ()) <- struct_construct()
+  (v6: core::option::Option::<core::box::Box::<@core::integer::u8>>) <- Option::None(v5)
+End:
+  Goto(blk3, {v6 -> v4})
+
+blk3:
+Statements:
+End:
+  Return(v4)
+
+//! > lowering_diagnostics

crates/cairo-lang-lowering/src/test_data/match

@@ -164,7 +164,7 @@ test_function_lowering(expect_diagnostics: false)
 
 //! > function
 fn foo(a: @Array::<felt252>) -> Option<Box<@felt252>> {
-    core::array::array_get(a, 0_u32)
+    core::array::array_get(a, 1_u32)
 }
 
 //! > function_name
@@ -180,7 +180,7 @@ foo
 Parameters: v0: core::RangeCheck, v1: @core::array::Array::<core::felt252>
 blk0 (root):
 Statements:
-  (v2: core::integer::u32) <- 0
+  (v2: core::integer::u32) <- 1
 End:
   Match(match core::array::array_get::<core::felt252>(v0, v1, v2) {
     Option::Some(v3, v4) => blk1,

crates/cairo-lang-starknet-classes/src/casm_contract_class_test.rs

@@ -100,7 +100,7 @@ fn test_contract_libfuncs_coverage(name: &str) {
 
 /// Tests that compiled_class_hash() returns the correct hash, by comparing it to hard-coded
 /// constant that was computed by other implementations.
-#[test_case("account__account", "1663b22c467591b6288c2e063fbad4cda6285ebe4861df9aa3d5bab3f479eb6")]
+#[test_case("account__account", "5191417f7d4b2560c387dd09a4a5aa2dfae8204c4f8a324d684a42fd32e46bc")]
 fn test_compiled_class_hash(name: &str, expected_hash: &str) {
     let compiled_json_path =
         get_example_file_path(format!("{name}.compiled_contract_class.json").as_str());