feat!: Brillig and AVM default all uninitialized memory cells to Field 0

avm-transpiler/src/instructions.rs

@@ -88,14 +88,13 @@ impl Default for AvmInstruction {
 #[allow(clippy::upper_case_acronyms, dead_code)]
 #[derive(Copy, Clone, Debug)]
 pub enum AvmTypeTag {
-    UNINITIALIZED,
+    FIELD,
     UINT1,
     UINT8,
     UINT16,
     UINT32,
     UINT64,
     UINT128,
-    FIELD,
     INVALID,
 }
 

avm-transpiler/src/transpile.rs

@@ -1497,6 +1497,5 @@ fn tag_from_bit_size(bit_size: BitSize) -> AvmTypeTag {
         BitSize::Integer(IntegerBitSize::U64) => AvmTypeTag::UINT64,
         BitSize::Integer(IntegerBitSize::U128) => AvmTypeTag::UINT128,
         BitSize::Field => AvmTypeTag::FIELD,
-        _ => panic!("The AVM doesn't support integer bit size {:?}", bit_size),
     }
 }

barretenberg/cpp/pil/avm/alu.pil

@@ -13,7 +13,7 @@ namespace alu(256);
     pol commit ic;
     pol commit sel_alu; // Predicate to activate the copy of intermediate registers to ALU table.
 
-    // Instruction tag (1: u1, 2: u8, 3: u16, 4: u32, 5: u64, 6: u128, 7: field) copied from Main table
+    // Instruction tag copied from Main table (MEM_TAG enum defined in constants)
     pol commit in_tag;
 
     // Flattened boolean instruction tags

barretenberg/cpp/pil/avm/constants_gen.pil

@@ -11,13 +11,13 @@ namespace constants(256);
     pol MAX_NULLIFIER_NON_EXISTENT_READ_REQUESTS_PER_CALL = 16;
     pol MAX_L1_TO_L2_MSG_READ_REQUESTS_PER_CALL = 16;
     pol MAX_UNENCRYPTED_LOGS_PER_CALL = 4;
+    pol MEM_TAG_FF = 0;
     pol MEM_TAG_U1 = 1;
     pol MEM_TAG_U8 = 2;
     pol MEM_TAG_U16 = 3;
     pol MEM_TAG_U32 = 4;
     pol MEM_TAG_U64 = 5;
     pol MEM_TAG_U128 = 6;
-    pol MEM_TAG_FF = 7;
     pol SENDER_KERNEL_INPUTS_COL_OFFSET = 0;
     pol ADDRESS_KERNEL_INPUTS_COL_OFFSET = 1;
     pol STORAGE_ADDRESS_KERNEL_INPUTS_COL_OFFSET = 1;

barretenberg/cpp/pil/avm/main.pil

@@ -152,7 +152,7 @@ namespace main(256);
     // Helper selector to characterize a Binary chiplet selector
     pol commit sel_bin;
 
-    // Instruction memory tags read/write (1: u1, 2: u8, 3: u16, 4: u32, 5: u64, 6: u128, 7: field)
+    // Instruction memory tags read/write (enum defined in constants)
     pol commit r_in_tag;
     pol commit w_in_tag;
     pol commit alu_in_tag; // Copy of r_in_tag or w_in_tag depending of the operation. It is sent to ALU trace.

barretenberg/cpp/pil/avm/mem.pil

@@ -9,7 +9,7 @@ namespace mem(256);
     pol commit addr;
     pol commit space_id;
     pol commit glob_addr;
-    pol commit tag; // Memory tag (0: uninitialized, 1: u1, 2: u8, 3: u16, 4: u32, 5: u64, 6: u128, 7:field)
+    pol commit tag; // Memory tag (MEM_TAG enum defined in constants)
     pol commit val;
     pol commit rw; // Enum: 0 (read), 1 (write)
     pol commit lastAccess; // Boolean (1 when this row is the last of a given address)
@@ -175,13 +175,16 @@ namespace mem(256);
     #[MEM_READ_WRITE_TAG_CONSISTENCY]
     (1 - lastAccess) * (1 - rw') * (tag' - tag) = 0;
 
+    // If this is the last row that an address is accessed, the next row must be the first access of another address.
     // Constrain that the first load from a given address has value 0. (Consistency of memory initialization.)
-    // We do not constrain that the tag == 0 as the 0 value is compatible with any memory type.
     // As we enforce lastAccess = 1 on the first row, the following condition applies also for the first memory entry:
     #[MEM_ZERO_INIT]
     lastAccess * (1 - rw') * val' = 0;
+    // Constrain that reading an uninitialized cell creates tag error unless it is expected to be of type FF.
+    #[MEM_ZERO_INIT_TAG_FF]
+    lastAccess * (1 - rw') * (tag' - constants.MEM_TAG_FF) = 0;
 
-    // TODO: Verfiy that skip_check_tag cannot be enabled maliciously by the prover.
+    // TODO: Verify that skip_check_tag cannot be enabled maliciously by the prover.
     // Skip check tag enabled for some MOV opcodes and RETURN opcode (sel_op_slice)
     #[SKIP_CHECK_TAG]
     skip_check_tag = sel_op_slice;
@@ -199,14 +202,13 @@ namespace mem(256);
     // instead of (r_in_tag - tag)^(-1) as this allows to store zero by default (i.e., when tag_err == 0).
     // The new column one_min_inv is set to 1 - (r_in_tag - tag)^(-1) when tag_err == 1
     // but must be set to 0 when tags are matching and tag_err = 0
-    // Relaxation: This relation is relaxed when skip_check_tag is enabled or for
-    // uninitialized memory, i.e. tag == 0.
+    // Relaxation: This relation is relaxed when skip_check_tag is enabled
     #[MEM_IN_TAG_CONSISTENCY_1]
-    tag * (1 - skip_check_tag) * (1 - rw) * ((r_in_tag - tag) * (1 - one_min_inv) - tag_err) = 0;
+    (1 - skip_check_tag) * (1 - rw) * ((r_in_tag - tag) * (1 - one_min_inv) - tag_err) = 0;
     // TODO: Try to decrease the degree of the above relation, e.g., skip_check_tag might be consolidated
     // with tag == 0 and rw == 1.
     #[MEM_IN_TAG_CONSISTENCY_2]
-    tag * (1 - tag_err) * one_min_inv = 0;
+    (1 - tag_err) * one_min_inv = 0;
 
     #[NO_TAG_ERR_WRITE_OR_SKIP]
     (skip_check_tag + rw) * tag_err = 0;

barretenberg/cpp/src/barretenberg/dsl/acir_format/serde/acir.hpp

@@ -145,12 +145,6 @@ struct BinaryIntOp {
 
 struct IntegerBitSize {
 
-    struct U0 {
-        friend bool operator==(const U0&, const U0&);
-        std::vector<uint8_t> bincodeSerialize() const;
-        static U0 bincodeDeserialize(std::vector<uint8_t>);
-    };
-
     struct U1 {
         friend bool operator==(const U1&, const U1&);
         std::vector<uint8_t> bincodeSerialize() const;
@@ -187,7 +181,7 @@ struct IntegerBitSize {
         static U128 bincodeDeserialize(std::vector<uint8_t>);
     };
 
-    std::variant<U0, U1, U8, U16, U32, U64, U128> value;
+    std::variant<U1, U8, U16, U32, U64, U128> value;
 
     friend bool operator==(const IntegerBitSize&, const IntegerBitSize&);
     std::vector<uint8_t> bincodeSerialize() const;
@@ -8061,46 +8055,6 @@ Program::IntegerBitSize serde::Deserializable<Program::IntegerBitSize>::deserial
 
 namespace Program {
 
-inline bool operator==(const IntegerBitSize::U0& lhs, const IntegerBitSize::U0& rhs)
-{
-    return true;
-}
-
-inline std::vector<uint8_t> IntegerBitSize::U0::bincodeSerialize() const
-{
-    auto serializer = serde::BincodeSerializer();
-    serde::Serializable<IntegerBitSize::U0>::serialize(*this, serializer);
-    return std::move(serializer).bytes();
-}
-
-inline IntegerBitSize::U0 IntegerBitSize::U0::bincodeDeserialize(std::vector<uint8_t> input)
-{
-    auto deserializer = serde::BincodeDeserializer(input);
-    auto value = serde::Deserializable<IntegerBitSize::U0>::deserialize(deserializer);
-    if (deserializer.get_buffer_offset() < input.size()) {
-        throw_or_abort("Some input bytes were not read");
-    }
-    return value;
-}
-
-} // end of namespace Program
-
-template <>
-template <typename Serializer>
-void serde::Serializable<Program::IntegerBitSize::U0>::serialize(const Program::IntegerBitSize::U0& obj,
-                                                                 Serializer& serializer)
-{}
-
-template <>
-template <typename Deserializer>
-Program::IntegerBitSize::U0 serde::Deserializable<Program::IntegerBitSize::U0>::deserialize(Deserializer& deserializer)
-{
-    Program::IntegerBitSize::U0 obj;
-    return obj;
-}
-
-namespace Program {
-
 inline bool operator==(const IntegerBitSize::U1& lhs, const IntegerBitSize::U1& rhs)
 {
     return true;

barretenberg/cpp/src/barretenberg/vm/avm/generated/relations/alu.hpp

@@ -21,13 +21,13 @@ template <typename FF_> class aluImpl {
                            [[maybe_unused]] const RelationParameters<FF>&,
                            [[maybe_unused]] const FF& scaling_factor)
     {
+        const auto constants_MEM_TAG_FF = FF(0);
         const auto constants_MEM_TAG_U1 = FF(1);
         const auto constants_MEM_TAG_U8 = FF(2);
         const auto constants_MEM_TAG_U16 = FF(3);
         const auto constants_MEM_TAG_U32 = FF(4);
         const auto constants_MEM_TAG_U64 = FF(5);
         const auto constants_MEM_TAG_U128 = FF(6);
-        const auto constants_MEM_TAG_FF = FF(7);
         const auto alu_MAX_BITS =
             ((((((new_term.alu_u1_tag * FF(1)) + (new_term.alu_u8_tag * FF(8))) + (new_term.alu_u16_tag * FF(16))) +
                (new_term.alu_u32_tag * FF(32))) +

barretenberg/cpp/src/barretenberg/vm/avm/generated/relations/main.hpp

@@ -23,8 +23,8 @@ template <typename FF_> class mainImpl {
                            [[maybe_unused]] const RelationParameters<FF>&,
                            [[maybe_unused]] const FF& scaling_factor)
     {
+        const auto constants_MEM_TAG_FF = FF(0);
         const auto constants_MEM_TAG_U1 = FF(1);
-        const auto constants_MEM_TAG_FF = FF(7);
         const auto constants_misc_INTERNAL_CALL_SPACE_ID = FF(255);
         const auto main_KERNEL_INPUT_SELECTORS =
             (((((((((((new_term.main_sel_op_address + new_term.main_sel_op_storage_address) +