feat: Reduce memory consumption by storing array length as u32 duri…

…ng SSA (#6606)

Co-authored-by: jfecher <jake@aztecprotocol.com>

compiler/noirc_evaluator/src/acir/acir_variable.rs

@@ -92,7 +92,7 @@ impl<'a> From<&'a SsaType> for AcirType {
             SsaType::Numeric(numeric_type) => AcirType::NumericType(*numeric_type),
             SsaType::Array(elements, size) => {
                 let elements = elements.iter().map(|e| e.into()).collect();
-                AcirType::Array(elements, *size)
+                AcirType::Array(elements, *size as usize)
             }
             _ => unreachable!("The type {value} cannot be represented in ACIR"),
         }

compiler/noirc_evaluator/src/acir/mod.rs

@@ -571,7 +571,7 @@ impl<'a> Context<'a> {
                 AcirValue::Array(_) => {
                     let block_id = self.block_id(param_id);
                     let len = if matches!(typ, Type::Array(_, _)) {
-                        typ.flattened_size()
+                        typ.flattened_size() as usize
                     } else {
                         return Err(InternalError::Unexpected {
                             expected: "Block params should be an array".to_owned(),
@@ -816,7 +816,9 @@ impl<'a> Context<'a> {
                                 let inputs = vecmap(arguments, |arg| self.convert_value(*arg, dfg));
                                 let output_count = result_ids
                                     .iter()
-                                    .map(|result_id| dfg.type_of_value(*result_id).flattened_size())
+                                    .map(|result_id| {
+                                        dfg.type_of_value(*result_id).flattened_size() as usize
+                                    })
                                     .sum();
 
                                 let Some(acir_function_id) =
@@ -948,7 +950,7 @@ impl<'a> Context<'a> {
                 let block_id = self.block_id(&array_id);
                 let array_typ = dfg.type_of_value(array_id);
                 let len = if matches!(array_typ, Type::Array(_, _)) {
-                    array_typ.flattened_size()
+                    array_typ.flattened_size() as usize
                 } else {
                     Self::flattened_value_size(&output)
                 };
@@ -1444,7 +1446,7 @@ impl<'a> Context<'a> {
         // a separate SSA value and restrictions on slice indices should be generated elsewhere in the SSA.
         let array_typ = dfg.type_of_value(array);
         let array_len = if !array_typ.contains_slice_element() {
-            array_typ.flattened_size()
+            array_typ.flattened_size() as usize
         } else {
             self.flattened_slice_size(array, dfg)
         };
@@ -1539,7 +1541,7 @@ impl<'a> Context<'a> {
                     let value = self.convert_value(array, dfg);
                     let array_typ = dfg.type_of_value(array);
                     let len = if !array_typ.contains_slice_element() {
-                        array_typ.flattened_size()
+                        array_typ.flattened_size() as usize
                     } else {
                         self.flattened_slice_size(array, dfg)
                     };
@@ -1810,7 +1812,7 @@ impl<'a> Context<'a> {
 
         return_values
             .iter()
-            .fold(0, |acc, value_id| acc + dfg.type_of_value(*value_id).flattened_size())
+            .fold(0, |acc, value_id| acc + dfg.type_of_value(*value_id).flattened_size() as usize)
     }
 
     /// Converts an SSA terminator's return values into their ACIR representations
@@ -2156,7 +2158,7 @@ impl<'a> Context<'a> {
                 let inputs = vecmap(&arguments_no_slice_len, |arg| self.convert_value(*arg, dfg));
 
                 let output_count = result_ids.iter().fold(0usize, |sum, result_id| {
-                    sum + dfg.try_get_array_length(*result_id).unwrap_or(1)
+                    sum + dfg.try_get_array_length(*result_id).unwrap_or(1) as usize
                 });
 
                 let vars = self.acir_context.black_box_function(black_box, inputs, output_count)?;
@@ -2180,7 +2182,7 @@ impl<'a> Context<'a> {
                         endian,
                         field,
                         radix,
-                        array_length as u32,
+                        array_length,
                         result_type[0].clone().into(),
                     )
                     .map(|array| vec![array])
@@ -2194,12 +2196,7 @@ impl<'a> Context<'a> {
                 };
 
                 self.acir_context
-                    .bit_decompose(
-                        endian,
-                        field,
-                        array_length as u32,
-                        result_type[0].clone().into(),
-                    )
+                    .bit_decompose(endian, field, array_length, result_type[0].clone().into())
                     .map(|array| vec![array])
             }
             Intrinsic::ArrayLen => {
@@ -2220,7 +2217,7 @@ impl<'a> Context<'a> {
                 let acir_value = self.convert_value(slice_contents, dfg);
 
                 let array_len = if !slice_typ.contains_slice_element() {
-                    slice_typ.flattened_size()
+                    slice_typ.flattened_size() as usize
                 } else {
                     self.flattened_slice_size(slice_contents, dfg)
                 };

compiler/noirc_evaluator/src/brillig/brillig_gen/brillig_block.rs

@@ -1823,7 +1823,7 @@ impl<'block> BrilligBlock<'block> {
                     Type::Array(_, nested_size) => {
                         let inner_array = BrilligArray {
                             pointer: self.brillig_context.allocate_register(),
-                            size: *nested_size,
+                            size: *nested_size as usize,
                         };
                         self.allocate_foreign_call_result_array(element_type, inner_array);
 

compiler/noirc_evaluator/src/brillig/brillig_gen/brillig_block_variables.rs

@@ -142,7 +142,7 @@ pub(crate) fn allocate_value<F, Registers: RegisterAllocator>(
         }
         Type::Array(item_typ, elem_count) => BrilligVariable::BrilligArray(BrilligArray {
             pointer: brillig_context.allocate_register(),
-            size: compute_array_length(&item_typ, elem_count),
+            size: compute_array_length(&item_typ, elem_count as usize),
         }),
         Type::Slice(_) => BrilligVariable::BrilligVector(BrilligVector {
             pointer: brillig_context.allocate_register(),

compiler/noirc_evaluator/src/brillig/brillig_gen/brillig_fn.rs

@@ -59,7 +59,7 @@ impl FunctionContext {
                 vecmap(item_type.iter(), |item_typ| {
                     FunctionContext::ssa_type_to_parameter(item_typ)
                 }),
-                *size,
+                *size as usize,
             ),
             Type::Slice(_) => {
                 panic!("ICE: Slice parameters cannot be derived from type information")

compiler/noirc_evaluator/src/brillig/brillig_ir/brillig_variable.rs

@@ -88,7 +88,7 @@ pub(crate) fn type_to_heap_value_type(typ: &Type) -> HeapValueType {
         ),
         Type::Array(elem_type, size) => HeapValueType::Array {
             value_types: elem_type.as_ref().iter().map(type_to_heap_value_type).collect(),
-            size: typ.element_size() * size,
+            size: typ.element_size() * *size as usize,
         },
         Type::Slice(elem_type) => HeapValueType::Vector {
             value_types: elem_type.as_ref().iter().map(type_to_heap_value_type).collect(),

compiler/noirc_evaluator/src/ssa/function_builder/data_bus.rs

@@ -160,7 +160,7 @@ impl FunctionBuilder {
         for value in values {
             self.add_to_data_bus(*value, &mut databus);
         }
-        let len = databus.values.len();
+        let len = databus.values.len() as u32;
 
         let array = (len > 0 && matches!(self.current_function.runtime(), RuntimeType::Acir(_)))
             .then(|| {
@@ -223,9 +223,11 @@ impl FunctionBuilder {
         ssa_params: &[ValueId],
         mut flattened_params_databus_visibility: Vec<DatabusVisibility>,
     ) -> Vec<DatabusVisibility> {
-        let ssa_param_sizes: Vec<_> = ssa_params
+        let ssa_param_sizes: Vec<usize> = ssa_params
             .iter()
-            .map(|ssa_param| self.current_function.dfg[*ssa_param].get_type().flattened_size())
+            .map(|ssa_param| {
+                self.current_function.dfg[*ssa_param].get_type().flattened_size() as usize
+            })
             .collect();
 
         let mut is_ssa_params_databus = Vec::with_capacity(ssa_params.len());

compiler/noirc_evaluator/src/ssa/ir/dfg.rs

@@ -307,13 +307,13 @@ impl DataFlowGraph {
         instruction_id: InstructionId,
         ctrl_typevars: Option<Vec<Type>>,
     ) {
-        self.results.insert(instruction_id, Default::default());
+        let result_types = self.instruction_result_types(instruction_id, ctrl_typevars);
+        let results = vecmap(result_types.into_iter().enumerate(), |(position, typ)| {
+            let instruction = instruction_id;
+            self.values.insert(Value::Instruction { typ, position, instruction })
+        });
 
-        // Get all of the types that this instruction produces
-        // and append them as results.
-        for typ in self.instruction_result_types(instruction_id, ctrl_typevars) {
-            self.append_result(instruction_id, typ);
-        }
+        self.results.insert(instruction_id, results);
     }
 
     /// Return the result types of this instruction.
@@ -370,22 +370,6 @@ impl DataFlowGraph {
         matches!(self.values[value].get_type(), Type::Reference(_))
     }
 
-    /// Appends a result type to the instruction.
-    pub(crate) fn append_result(&mut self, instruction_id: InstructionId, typ: Type) -> ValueId {
-        let results = self.results.get_mut(&instruction_id).unwrap();
-        let expected_res_position = results.len();
-
-        let value_id = self.values.insert(Value::Instruction {
-            typ,
-            position: expected_res_position,
-            instruction: instruction_id,
-        });
-
-        // Add value to the list of results for this instruction
-        results.push(value_id);
-        value_id
-    }
-
     /// Replaces an instruction result with a fresh id.
     pub(crate) fn replace_result(
         &mut self,
@@ -463,7 +447,7 @@ impl DataFlowGraph {
 
     /// If this value is an array, return the length of the array as indicated by its type.
     /// Otherwise, return None.
-    pub(crate) fn try_get_array_length(&self, value: ValueId) -> Option<usize> {
+    pub(crate) fn try_get_array_length(&self, value: ValueId) -> Option<u32> {
         match self.type_of_value(value) {
             Type::Array(_, length) => Some(length),
             _ => None,

compiler/noirc_evaluator/src/ssa/ir/instruction/call.rs

@@ -56,7 +56,7 @@ pub(super) fn simplify_call(
             if let (Some(constant_args), Some(return_type)) = (constant_args, return_type.clone()) {
                 let field = constant_args[0];
                 let limb_count = if let Type::Array(_, array_len) = return_type {
-                    array_len as u32
+                    array_len
                 } else {
                     unreachable!("ICE: Intrinsic::ToRadix return type must be array")
                 };
@@ -73,7 +73,7 @@ pub(super) fn simplify_call(
                 let field = constant_args[0];
                 let radix = constant_args[1].to_u128() as u32;
                 let limb_count = if let Type::Array(_, array_len) = return_type {
-                    array_len as u32
+                    array_len
                 } else {
                     unreachable!("ICE: Intrinsic::ToRadix return type must be array")
                 };
@@ -361,7 +361,7 @@ pub(super) fn simplify_call(
         Intrinsic::IsUnconstrained => SimplifyResult::None,
         Intrinsic::DerivePedersenGenerators => {
             if let Some(Type::Array(_, len)) = return_type.clone() {
-                simplify_derive_generators(dfg, arguments, len as u32, block, call_stack)
+                simplify_derive_generators(dfg, arguments, len, block, call_stack)
             } else {
                 unreachable!("Derive Pedersen Generators must return an array");
             }
@@ -442,8 +442,8 @@ fn simplify_slice_push_back(
     for elem in &arguments[2..] {
         slice.push_back(*elem);
     }
-    let slice_size = slice.len();
-    let element_size = element_type.element_size();
+    let slice_size = slice.len() as u32;
+    let element_size = element_type.element_size() as u32;
     let new_slice = make_array(dfg, slice, element_type, block, &call_stack);
 
     let set_last_slice_value_instr = Instruction::ArraySet {
@@ -632,7 +632,7 @@ fn make_constant_array(
     let result_constants: im::Vector<_> =
         results.map(|element| dfg.make_constant(element, typ.clone())).collect();
 
-    let typ = Type::Array(Arc::new(vec![typ]), result_constants.len());
+    let typ = Type::Array(Arc::new(vec![typ]), result_constants.len() as u32);
     make_array(dfg, result_constants, typ, block, call_stack)
 }
 
@@ -819,7 +819,7 @@ fn simplify_derive_generators(
                 results.push(dfg.make_constant(y, Type::field()));
                 results.push(is_infinite);
             }
-            let len = results.len();
+            let len = results.len() as u32;
             let typ =
                 Type::Array(vec![Type::field(), Type::field(), Type::unsigned(1)].into(), len / 3);
             let result = make_array(dfg, results.into(), typ, block, call_stack);

compiler/noirc_evaluator/src/ssa/ir/types.rs

@@ -75,7 +75,7 @@ pub(crate) enum Type {
     Reference(Arc<Type>),
 
     /// An immutable array value with the given element type and length
-    Array(Arc<CompositeType>, usize),
+    Array(Arc<CompositeType>, u32),
 
     /// An immutable slice value with a given element type
     Slice(Arc<CompositeType>),
@@ -111,7 +111,7 @@ impl Type {
     }
 
     /// Creates the str<N> type, of the given length N
-    pub(crate) fn str(length: usize) -> Type {
+    pub(crate) fn str(length: u32) -> Type {
         Type::Array(Arc::new(vec![Type::char()]), length)
     }
 
@@ -161,7 +161,7 @@ impl Type {
     }
 
     /// Returns the flattened size of a Type
-    pub(crate) fn flattened_size(&self) -> usize {
+    pub(crate) fn flattened_size(&self) -> u32 {
         match self {
             Type::Array(elements, len) => {
                 elements.iter().fold(0, |sum, elem| sum + (elem.flattened_size() * len))

compiler/noirc_evaluator/src/ssa/opt/as_slice_length.rs

@@ -33,7 +33,7 @@ impl Function {
     }
 }
 
-fn known_slice_lengths(func: &Function) -> HashMap<InstructionId, usize> {
+fn known_slice_lengths(func: &Function) -> HashMap<InstructionId, u32> {
     let mut known_slice_lengths = HashMap::default();
     for block_id in func.reachable_blocks() {
         let block = &func.dfg[block_id];
@@ -61,7 +61,7 @@ fn known_slice_lengths(func: &Function) -> HashMap<InstructionId, usize> {
 
 fn replace_known_slice_lengths(
     func: &mut Function,
-    known_slice_lengths: HashMap<InstructionId, usize>,
+    known_slice_lengths: HashMap<InstructionId, u32>,
 ) {
     known_slice_lengths.into_iter().for_each(|(instruction_id, known_length)| {
         let call_returns = func.dfg.instruction_results(instruction_id);

compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs

@@ -726,7 +726,7 @@ pub(crate) fn type_to_brillig_parameter(typ: &Type) -> Option<BrilligParameter>
             for item_typ in item_type.iter() {
                 parameters.push(type_to_brillig_parameter(item_typ)?);
             }
-            Some(BrilligParameter::Array(parameters, *size))
+            Some(BrilligParameter::Array(parameters, *size as usize))
         }
         _ => None,
     }

compiler/noirc_evaluator/src/ssa/opt/flatten_cfg/capacity_tracker.rs

@@ -21,7 +21,7 @@ impl<'a> SliceCapacityTracker<'a> {
     pub(crate) fn collect_slice_information(
         &self,
         instruction: &Instruction,
-        slice_sizes: &mut HashMap<ValueId, usize>,
+        slice_sizes: &mut HashMap<ValueId, u32>,
         results: &[ValueId],
     ) {
         match instruction {
@@ -106,13 +106,12 @@ impl<'a> SliceCapacityTracker<'a> {
                         Intrinsic::ToBits(_) => {
                             // Compiler sanity check
                             assert!(matches!(self.dfg.type_of_value(result_slice), Type::Slice(_)));
-                            slice_sizes.insert(result_slice, FieldElement::max_num_bits() as usize);
+                            slice_sizes.insert(result_slice, FieldElement::max_num_bits());
                         }
                         Intrinsic::ToRadix(_) => {
                             // Compiler sanity check
                             assert!(matches!(self.dfg.type_of_value(result_slice), Type::Slice(_)));
-                            slice_sizes
-                                .insert(result_slice, FieldElement::max_num_bytes() as usize);
+                            slice_sizes.insert(result_slice, FieldElement::max_num_bytes());
                         }
                         Intrinsic::AsSlice => {
                             let array_size = self
@@ -157,15 +156,15 @@ impl<'a> SliceCapacityTracker<'a> {
     pub(crate) fn compute_slice_capacity(
         &self,
         array_id: ValueId,
-        slice_sizes: &mut HashMap<ValueId, usize>,
+        slice_sizes: &mut HashMap<ValueId, u32>,
     ) {
         if let Some((array, typ)) = self.dfg.get_array_constant(array_id) {
             // Compiler sanity check
             assert!(!typ.is_nested_slice(), "ICE: Nested slices are not allowed and should not have reached the flattening pass of SSA");
             if let Type::Slice(_) = typ {
                 let element_size = typ.element_size();
                 let len = array.len() / element_size;
-                slice_sizes.insert(array_id, len);
+                slice_sizes.insert(array_id, len as u32);
             }
         }
     }