Remove bounds checks from array_get.

corelib/src/array.cairo

@@ -27,10 +27,9 @@ extern fn array_snapshot_multi_pop_front<PoppedT, impl Info: FixedSizedArrayInfo
 extern fn array_snapshot_multi_pop_back<PoppedT, impl Info: FixedSizedArrayInfo<PoppedT>>(
     ref arr: @Array<Info::Element>
 ) -> Option<@Box<PoppedT>> implicits(RangeCheck) nopanic;
-#[panic_with('Index out of bounds', array_at)]
 extern fn array_get<T>(
     arr: @Array<T>, index: usize
-) -> Option<Box<@T>> implicits(RangeCheck) nopanic;
+) -> Box<@T> nopanic;
 extern fn array_slice<T>(
     arr: @Array<T>, start: usize, length: usize
 ) -> Option<@Array<T>> implicits(RangeCheck) nopanic;
@@ -121,7 +120,7 @@ pub impl ArrayImpl<T> of ArrayTrait<T> {
     /// ```
     #[inline(always)]
     fn get(self: @Array<T>, index: usize) -> Option<Box<@T>> {
-        array_get(self, index)
+        Option::Some(array_get(self, index))
     }
     /// Returns a snapshot of the value at the given 'index'.
     ///
@@ -132,7 +131,7 @@ pub impl ArrayImpl<T> of ArrayTrait<T> {
     /// assert!(arr.at(1) == @4);
     /// ```
     fn at(self: @Array<T>, index: usize) -> @T {
-        array_at(self, index).unbox()
+        array_get(self, index).unbox()
     }
     /// Returns the length of the array.
     ///
@@ -183,7 +182,7 @@ impl ArrayDefault<T> of Default<Array<T>> {
 
 impl ArrayIndex<T> of IndexView<Array<T>, usize, @T> {
     fn index(self: @Array<T>, index: usize) -> @T {
-        array_at(self, index).unbox()
+        array_get(self, index).unbox()
     }
 }
 
@@ -347,7 +346,7 @@ pub impl SpanImpl<T> of SpanTrait<T> {
     /// ```
     #[inline(always)]
     fn get(self: Span<T>, index: usize) -> Option<Box<@T>> {
-        array_get(self.snapshot, index)
+        Option::Some(array_get(self.snapshot, index))
     }
     /// Returns a snapshot of the value at the given 'index'.
     ///
@@ -358,7 +357,7 @@ pub impl SpanImpl<T> of SpanTrait<T> {
     /// ```
     #[inline(always)]
     fn at(self: Span<T>, index: usize) -> @T {
-        array_at(self.snapshot, index).unbox()
+        array_get(self.snapshot, index).unbox()
     }
     /// Returns a span containing values from the 'start' index, with
     /// amount equal to 'length'.
@@ -406,7 +405,7 @@ pub impl SpanImpl<T> of SpanTrait<T> {
 pub impl SpanIndex<T> of IndexView<Span<T>, usize, @T> {
     #[inline(always)]
     fn index(self: @Span<T>, index: usize) -> @T {
-        array_at(*self.snapshot, index).unbox()
+        array_get(*self.snapshot, index).unbox()
     }
 }
 

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

@@ -164,7 +164,7 @@ test_function_lowering
 
 //! > function
 fn foo(a: @Array::<felt252>) -> Option<Box<@felt252>> {
-    core::array::array_get(a, 0_u32)
+    Option::Some(core::array::array_get(a, 0_u32))
 }
 
 //! > function_name
@@ -177,28 +177,14 @@ foo
 //! > lowering_diagnostics
 
 //! > lowering_flat
-Parameters: v0: core::RangeCheck, v1: @core::array::Array::<core::felt252>
+Parameters: v0: @core::array::Array::<core::felt252>
 blk0 (root):
 Statements:
-  (v2: core::integer::u32) <- 0
+  (v1: core::integer::u32) <- 0
+  (v2: core::box::Box::<@core::felt252>) <- core::array::array_get::<core::felt252>(v0, v1)
+  (v3: core::option::Option::<core::box::Box::<@core::felt252>>) <- Option::Some(v2)
 End:
-  Match(match core::array::array_get::<core::felt252>(v0, v1, v2) {
-    Option::Some(v3, v4) => blk1,
-    Option::None(v5) => blk2,
-  })
-
-blk1:
-Statements:
-  (v6: core::option::Option::<core::box::Box::<@core::felt252>>) <- Option::Some(v4)
-End:
-  Return(v3, v6)
-
-blk2:
-Statements:
-  (v7: ()) <- struct_construct()
-  (v8: core::option::Option::<core::box::Box::<@core::felt252>>) <- Option::None(v7)
-End:
-  Return(v5, v8)
+  Return(v3)
 
 //! > ==========================================================================
 

crates/cairo-lang-sierra-ap-change/src/core_libfunc_ap_change.rs

@@ -84,7 +84,7 @@ pub fn core_libfunc_ap_change<InfoProvider: InvocationApChangeInfoProvider>(
                 vec![ApChange::Known(3), ApChange::Known(3)]
             }
             ArrayConcreteLibfunc::Get(libfunc) => {
-                if info_provider.type_size(&libfunc.ty) == 1 { [4, 3] } else { [5, 4] }
+                if info_provider.type_size(&libfunc.ty) == 1 { [0] } else { [1] }
                     .map(ApChange::Known)
                     .to_vec()
             }

crates/cairo-lang-sierra-gas/src/core_libfunc_cost_base.rs

@@ -280,15 +280,9 @@ pub fn core_libfunc_cost(
             }
             ArrayConcreteLibfunc::Get(libfunc) => {
                 if info_provider.type_size(&libfunc.ty) == 1 {
-                    vec![
-                        (ConstCost::steps(5) + ConstCost::range_checks(1)).into(),
-                        (ConstCost::steps(5) + ConstCost::range_checks(1)).into(),
-                    ]
+                    vec![(ConstCost::steps(0)).into()]
                 } else {
-                    vec![
-                        (ConstCost::steps(6) + ConstCost::range_checks(1)).into(),
-                        (ConstCost::steps(6) + ConstCost::range_checks(1)).into(),
-                    ]
+                    vec![(ConstCost::steps(1)).into()]
                 }
             }
             ArrayConcreteLibfunc::Slice(libfunc) => {

crates/cairo-lang-sierra-to-casm/src/invocations/array.rs

@@ -213,9 +213,8 @@ fn build_array_get(
     elem_ty: &ConcreteTypeId,
     builder: CompiledInvocationBuilder<'_>,
 ) -> Result<CompiledInvocation, InvocationError> {
-    let [expr_range_check, expr_arr, expr_index] = builder.try_get_refs()?;
-    let range_check = expr_range_check.try_unpack_single()?;
-    let [arr_start, arr_end] = expr_arr.try_unpack()?;
+    let [expr_arr, expr_index] = builder.try_get_refs()?;
+    let [arr_start, _arr_end] = expr_arr.try_unpack()?;
     let index = expr_index.try_unpack_single()?;
 
     let element_size = builder.program_info.type_sizes[elem_ty];
@@ -224,54 +223,16 @@ fn build_array_get(
     add_input_variables! {casm_builder,
         deref_or_immediate index;
         deref arr_start;
-        deref arr_end;
-        buffer(1) range_check;
     };
     casm_build_extend! {casm_builder,
         const element_size = element_size;
-        let orig_range_check = range_check;
-        // Compute the length of the array (in cells).
-        tempvar array_length_in_cells = arr_end - arr_start;
-        // Compute the offset of the element (in cells).
         maybe_tempvar element_offset_in_cells = index * element_size;
-        // Check that offset is in range.
-        // Note that the offset may be as large as `(2^15 - 1) * (2^32 - 1)`.
-        tempvar is_in_range;
-        hint TestLessThan {lhs: element_offset_in_cells, rhs: array_length_in_cells} into {dst: is_in_range};
-        jump InRange if is_in_range != 0;
-        // Index out of bounds. Compute offset - length.
-        tempvar offset_length_diff = element_offset_in_cells - array_length_in_cells;
-        // Assert offset - length >= 0. Note that offset_length_diff is smaller than 2^128 as the index type is u32.
-        assert offset_length_diff  = *(range_check++);
-        jump FailureHandle;
-
-        InRange:
-        // Assert offset < length, or that length - (offset + 1) is in [0, 2^128).
-        // Compute offset + 1.
-        const one = 1;
-        tempvar element_offset_in_cells_plus_1 = element_offset_in_cells + one;
-        // Compute length - (offset + 1).
-        tempvar offset_length_diff = array_length_in_cells - element_offset_in_cells_plus_1;
-        // Assert length - (offset + 1) is in [0, 2^128).
-        assert offset_length_diff = *(range_check++);
-         // The start address of target cells.
         let target_cell = arr_start + element_offset_in_cells;
     };
-    let failure_handle = get_non_fallthrough_statement_id(&builder);
     Ok(builder.build_from_casm_builder(
         casm_builder,
-        [
-            ("Fallthrough", &[&[range_check], &[target_cell]], None),
-            ("FailureHandle", &[&[range_check]], Some(failure_handle)),
-        ],
-        CostValidationInfo {
-            builtin_infos: vec![BuiltinInfo {
-                cost_token_ty: CostTokenType::RangeCheck,
-                start: orig_range_check,
-                end: range_check,
-            }],
-            extra_costs: None,
-        },
+        [("Fallthrough", &[&[target_cell]], None)],
+        CostValidationInfo { builtin_infos: vec![], extra_costs: None },
     ))
 }
 

crates/cairo-lang-sierra/src/extensions/modules/array.rs

@@ -334,29 +334,19 @@ impl SignatureAndTypeGenericLibfunc for ArrayGetLibfuncWrapped {
         ty: ConcreteTypeId,
     ) -> Result<LibfuncSignature, SpecializationError> {
         let arr_type = context.get_wrapped_concrete_type(ArrayType::id(), ty.clone())?;
-        let range_check_type = context.get_concrete_type(RangeCheckType::id(), &[])?;
         let index_type = context.get_concrete_type(ArrayIndexType::id(), &[])?;
         let param_signatures = vec![
-            ParamSignature::new(range_check_type.clone()).with_allow_add_const(),
             ParamSignature::new(snapshot_ty(context, arr_type)?),
             ParamSignature::new(index_type),
         ];
-        let rc_output_info = OutputVarInfo::new_builtin(range_check_type, 0);
         let branch_signatures = vec![
             // First (success) branch returns rc, array and element; failure branch does not return
             // an element.
             BranchSignature {
-                vars: vec![
-                    rc_output_info.clone(),
-                    OutputVarInfo {
-                        ty: box_ty(context, snapshot_ty(context, ty)?)?,
-                        ref_info: OutputVarReferenceInfo::Deferred(DeferredOutputKind::Generic),
-                    },
-                ],
-                ap_change: SierraApChange::Known { new_vars_only: false },
-            },
-            BranchSignature {
-                vars: vec![rc_output_info],
+                vars: vec![OutputVarInfo {
+                    ty: box_ty(context, snapshot_ty(context, ty)?)?,
+                    ref_info: OutputVarReferenceInfo::Deferred(DeferredOutputKind::Generic),
+                }],
                 ap_change: SierraApChange::Known { new_vars_only: false },
             },
         ];