feat: add support for u1 in the avm circuit & witgen

avm-transpiler/src/bit_traits.rs

@@ -58,15 +58,15 @@ impl BitsQueryable for usize {
 
 pub fn bits_needed_for<T: BitsQueryable>(val: &T) -> usize {
     let num_bits = val.num_bits();
-    if num_bits < 8 {
+    if num_bits <= 8 {
         8
-    } else if num_bits < 16 {
+    } else if num_bits <= 16 {
         16
-    } else if num_bits < 32 {
+    } else if num_bits <= 32 {
         32
-    } else if num_bits < 64 {
+    } else if num_bits <= 64 {
         64
-    } else if num_bits < 128 {
+    } else if num_bits <= 128 {
         128
     } else {
         254

avm-transpiler/src/instructions.rs

@@ -94,6 +94,7 @@ impl Default for AvmInstruction {
 #[derive(Copy, Clone, Debug)]
 pub enum AvmTypeTag {
     UNINITIALIZED,
+    UINT1,
     UINT8,
     UINT16,
     UINT32,
@@ -107,6 +108,7 @@ pub enum AvmTypeTag {
 /// Constants (as used by the SET instruction) can have size
 /// different from 32 bits
 pub enum AvmOperand {
+    U1 { value: u8 }, // same wire format as U8
     U8 { value: u8 },
     U16 { value: u16 },
     U32 { value: u32 },
@@ -118,6 +120,7 @@ pub enum AvmOperand {
 impl Display for AvmOperand {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match self {
+            AvmOperand::U1 { value } => write!(f, " U1:{}", value),
             AvmOperand::U8 { value } => write!(f, " U8:{}", value),
             AvmOperand::U16 { value } => write!(f, " U16:{}", value),
             AvmOperand::U32 { value } => write!(f, " U32:{}", value),
@@ -131,6 +134,7 @@ impl Display for AvmOperand {
 impl AvmOperand {
     pub fn to_be_bytes(&self) -> Vec<u8> {
         match self {
+            AvmOperand::U1 { value } => value.to_be_bytes().to_vec(),
             AvmOperand::U8 { value } => value.to_be_bytes().to_vec(),
             AvmOperand::U16 { value } => value.to_be_bytes().to_vec(),
             AvmOperand::U32 { value } => value.to_be_bytes().to_vec(),

avm-transpiler/src/transpile.rs

@@ -202,15 +202,6 @@ pub fn brillig_to_avm(
                     ],
                     tag: Some(tag_from_bit_size(BitSize::Integer(*bit_size))),
                 });
-                if let IntegerBitSize::U1 = bit_size {
-                    // We need to cast the result back to u1
-                    handle_cast(
-                        &mut avm_instrs,
-                        destination,
-                        destination,
-                        BitSize::Integer(IntegerBitSize::U1),
-                    );
-                }
             }
             BrilligOpcode::CalldataCopy { destination_address, size_address, offset_address } => {
                 avm_instrs.push(AvmInstruction {
@@ -505,32 +496,8 @@ fn handle_cast(
     let source_offset = source.to_usize() as u32;
     let dest_offset = destination.to_usize() as u32;
 
-    if bit_size == BitSize::Integer(IntegerBitSize::U1) {
-        assert!(
-            matches!(tag_from_bit_size(bit_size), AvmTypeTag::UINT8),
-            "If u1 doesn't map to u8 anymore, change this code!"
-        );
-        avm_instrs.extend([
-            // We cast to Field to be able to use toradix.
-            generate_cast_instruction(source_offset, false, dest_offset, false, AvmTypeTag::FIELD),
-            // Toradix with radix 2 and 1 limb is the same as modulo 2.
-            // We need to insert an instruction explicitly because we want to fine-tune 'indirect'.
-            AvmInstruction {
-                opcode: AvmOpcode::TORADIXLE,
-                indirect: Some(ALL_DIRECT),
-                tag: None,
-                operands: vec![
-                    AvmOperand::U32 { value: dest_offset },
-                    AvmOperand::U32 { value: dest_offset },
-                    AvmOperand::U32 { value: /*radix=*/ 2},
-                    AvmOperand::U32 { value: /*limbs=*/ 1},
-                ],
-            },
-        ]);
-    } else {
-        let tag = tag_from_bit_size(bit_size);
-        avm_instrs.push(generate_cast_instruction(source_offset, false, dest_offset, false, tag));
-    }
+    let tag = tag_from_bit_size(bit_size);
+    avm_instrs.push(generate_cast_instruction(source_offset, false, dest_offset, false, tag));
 }
 
 /// Handle an AVM NOTEHASHEXISTS instruction
@@ -987,12 +954,11 @@ fn handle_black_box_function(avm_instrs: &mut Vec<AvmInstruction>, operation: &B
                 ..Default::default()
             });
         }
-        // We ignore the output bits flag since we represent bits as bytes
-        BlackBoxOp::ToRadix { input, radix, output, output_bits: _ } => {
+        BlackBoxOp::ToRadix { input, radix, output, output_bits } => {
             let num_limbs = output.size as u32;
             let input_offset = input.0 as u32;
             let output_offset = output.pointer.0 as u32;
-            assert!(radix <= &256u32, "Radix must be less than or equal to 256");
+            let radix_offset = radix.0 as u32;
 
             avm_instrs.push(AvmInstruction {
                 opcode: AvmOpcode::TORADIXLE,
@@ -1001,8 +967,9 @@ fn handle_black_box_function(avm_instrs: &mut Vec<AvmInstruction>, operation: &B
                 operands: vec![
                     AvmOperand::U32 { value: input_offset },
                     AvmOperand::U32 { value: output_offset },
-                    AvmOperand::U32 { value: *radix },
+                    AvmOperand::U32 { value: radix_offset },
                     AvmOperand::U32 { value: num_limbs },
+                    AvmOperand::U1 { value: *output_bits as u8 },
                 ],
             });
         }
@@ -1313,8 +1280,6 @@ pub fn map_brillig_pcs_to_avm_pcs(brillig_bytecode: &[BrilligOpcode<FieldElement
     pc_map[0] = 0; // first PC is always 0 as there are no instructions inserted by AVM at start
     for i in 0..brillig_bytecode.len() - 1 {
         let num_avm_instrs_for_this_brillig_instr = match &brillig_bytecode[i] {
-            BrilligOpcode::Cast { bit_size: BitSize::Integer(IntegerBitSize::U1), .. } => 2,
-            BrilligOpcode::Not { bit_size: IntegerBitSize::U1, .. } => 3,
             _ => 1,
         };
         // next Brillig pc will map to an AVM pc offset by the
@@ -1338,7 +1303,7 @@ fn is_integral_bit_size(bit_size: IntegerBitSize) -> bool {
 
 fn tag_from_bit_size(bit_size: BitSize) -> AvmTypeTag {
     match bit_size {
-        BitSize::Integer(IntegerBitSize::U1) => AvmTypeTag::UINT8, // temp workaround
+        BitSize::Integer(IntegerBitSize::U1) => AvmTypeTag::UINT1,
         BitSize::Integer(IntegerBitSize::U8) => AvmTypeTag::UINT8,
         BitSize::Integer(IntegerBitSize::U16) => AvmTypeTag::UINT16,
         BitSize::Integer(IntegerBitSize::U32) => AvmTypeTag::UINT32,

barretenberg/cpp/pil/avm/alu.pil

@@ -1,3 +1,4 @@
+include "constants_gen.pil";
 include "gadgets/range_check.pil";
 include "gadgets/cmp.pil";
 namespace alu(256);
@@ -12,16 +13,17 @@ namespace alu(256);
     pol commit ic;
     pol commit sel_alu; // Predicate to activate the copy of intermediate registers to ALU table.
 
-    // Instruction tag (1: u8, 2: u16, 3: u32, 4: u64, 5: u128, 6: field) copied from Main table
+    // Instruction tag (1: u1, 2: u8, 3: u16, 4: u32, 5: u64, 6: u128, 7: field) copied from Main table
     pol commit in_tag;
 
     // Flattened boolean instruction tags
-    pol commit ff_tag;
+    pol commit u1_tag;
     pol commit u8_tag;
     pol commit u16_tag;
     pol commit u32_tag;
     pol commit u64_tag;
     pol commit u128_tag;
+    pol commit ff_tag;
 
     // Compute predicate telling whether there is a row entry in the ALU table.
     sel_alu = op_add + op_sub + op_mul + op_not + op_eq + op_cast + op_lt + op_lte + op_shr + op_shl + op_div;
@@ -30,18 +32,25 @@ namespace alu(256);
     // Remark: Operation selectors are constrained in the main trace.
 
     // Boolean flattened instructions tags
-    ff_tag * (1 - ff_tag) = 0;
+    u1_tag * (1 - u1_tag) = 0;
     u8_tag * (1 - u8_tag) = 0;
     u16_tag * (1 - u16_tag) = 0;
     u32_tag * (1 - u32_tag) = 0;
     u64_tag * (1 - u64_tag) = 0;
     u128_tag * (1 - u128_tag) = 0;
+    ff_tag * (1 - ff_tag) = 0;
 
     // Mutual exclusion of the flattened instruction tag.
-    sel_alu * (ff_tag + u8_tag + u16_tag + u32_tag + u64_tag + u128_tag - 1) = 0;
+    sel_alu * (u1_tag + u8_tag + u16_tag + u32_tag + u64_tag + u128_tag + ff_tag - 1) = 0;
 
     // Correct flattening of the instruction tag.
-    in_tag = u8_tag + 2 * u16_tag + 3 * u32_tag + 4 * u64_tag + 5 * u128_tag + 6 * ff_tag;
+    in_tag = u1_tag // * 1 (constants.MEM_TAG_U1)
+           + (constants.MEM_TAG_U8 * u8_tag)
+           + (constants.MEM_TAG_U16 * u16_tag)
+           + (constants.MEM_TAG_U32 * u32_tag)
+           + (constants.MEM_TAG_U64 * u64_tag)
+           + (constants.MEM_TAG_U128 * u128_tag)
+           + (constants.MEM_TAG_FF * ff_tag);
 
     // Operation selectors are copied from main table and do not need to be constrained here.
     // Mutual exclusion of op_add and op_sub are derived from their mutual exclusion in the
@@ -59,7 +68,7 @@ namespace alu(256);
     range_check_input_value = (op_add + op_sub + op_mul + op_cast + op_div) * ic + (op_shr * a_hi * NON_TRIVIAL_SHIFT) + (op_shl * a_lo * NON_TRIVIAL_SHIFT);
     // The allowed bit range is defined by the instr tag, unless in shifts where it's different
     range_check_num_bits = 
-        (op_add + op_sub + op_mul + op_cast + op_div) * (u8_tag * 8 + u16_tag * 16 + u32_tag * 32 + u64_tag * 64 + u128_tag * 128) + 
+        (op_add + op_sub + op_mul + op_cast + op_div) * (u1_tag * 1 + u8_tag * 8 + u16_tag * 16 + u32_tag * 32 + u64_tag * 64 + u128_tag * 128) + 
         (op_shl + op_shr) * (MAX_BITS - ib) * NON_TRIVIAL_SHIFT;
 
     // Permutation to the Range Check Gadget
@@ -92,15 +101,16 @@ namespace alu(256);
     // These are useful and commonly used relations / columns used through the file 
 
     // The maximum number of bits as defined by the instr tag
-    pol MAX_BITS = u8_tag * 8 + u16_tag * 16 + u32_tag * 32 + u64_tag * 64 + u128_tag * 128;
+    pol MAX_BITS = u1_tag * 1 + u8_tag * 8 + u16_tag * 16 + u32_tag * 32 + u64_tag * 64 + u128_tag * 128;
     // 2^MAX_BITS
-    pol MAX_BITS_POW = u8_tag * 2**8 + u16_tag * 2**16 + u32_tag * 2**32 + u64_tag * 2**64 + u128_tag * 2**128;
+    pol MAX_BITS_POW = u1_tag * 2 + u8_tag * 2**8 + u16_tag * 2**16 + u32_tag * 2**32 + u64_tag * 2**64 + u128_tag * 2**128;
     pol UINT_MAX = MAX_BITS_POW - 1;
 
     // Value of p - 1
     pol MAX_FIELD_VALUE = 21888242871839275222246405745257275088548364400416034343698204186575808495616;
 
     // Used when we split inputs into lo and hi limbs each of (MAX_BITS / 2)
+    // omitted: u1_tag * 0 (no need for limbs...)
     pol LIMB_BITS_POW = u8_tag * 2**4 + u16_tag * 2**8 + u32_tag * 2**16 + u64_tag * 2**32 + u128_tag * 2**64;
     // Lo and Hi Limbs for ia, ib and ic resp. Useful when performing operations over integers
     pol commit a_lo;
@@ -132,7 +142,8 @@ namespace alu(256);
     a_lo * b_hi + b_lo * a_hi = partial_prod_lo + LIMB_BITS_POW * partial_prod_hi;
 
     // This holds the product over the integers
-    pol PRODUCT = a_lo * b_lo + LIMB_BITS_POW * partial_prod_lo + MAX_BITS_POW * (partial_prod_hi + a_hi * b_hi);
+    // (u1 multiplication only cares about a_lo and b_lo)
+    pol PRODUCT = a_lo * b_lo + (1 - u1_tag) * (LIMB_BITS_POW * partial_prod_lo + MAX_BITS_POW * (partial_prod_hi + a_hi * b_hi));
 
     // =============== ADDITION/SUBTRACTION Operation Constraints ================================================= 
     pol commit op_add;
@@ -243,6 +254,7 @@ namespace alu(256);
 
     // =============== Trivial Shift Operation ================================================= 
     // We use the comparison gadget to test ib > (MAX_BITS - 1)
+    // (always true for u1 - all u1 shifts are trivial)
     (op_shl + op_shr) * (cmp_gadget_input_a - ib) = 0;
     (op_shl + op_shr) * (cmp_gadget_input_b - (MAX_BITS - 1) ) = 0;
 

barretenberg/cpp/pil/avm/binary.pil

@@ -13,7 +13,7 @@ namespace binary(256);
     pol commit acc_ib;
     pol commit acc_ic;
 
-    // This is the instruction tag {1,2,3,4,5} (restricted to not be a field)
+    // This is the instruction tag {1,2,3,4,5,6} (restricted to not be a field)
     // Operations over FF are not supported, it is assumed this exclusion is handled
     // outside of this subtrace.
 
@@ -37,7 +37,7 @@ namespace binary(256);
 
     // To support dynamically sized memory operands we use a counter against a lookup
     // This decrementing counter goes from [MEM_TAG, 0] where MEM_TAG is the number of bytes in the
-    // corresponding integer. i.e. MEM_TAG is between 1 (U8) and 16(U128).
+    // corresponding integer. i.e. MEM_TAG is between 1 (U8) and 16 (U128).
     // Consistency can be achieved with a lookup table between the instr_tag and bytes_length
     pol commit mem_tag_ctr;
     #[MEM_TAG_REL]

barretenberg/cpp/pil/avm/constants_gen.pil

@@ -11,6 +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_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_SELECTOR = 0;
     pol ADDRESS_SELECTOR = 1;
     pol STORAGE_ADDRESS_SELECTOR = 1;

barretenberg/cpp/pil/avm/fixed/byte_lookup.pil

@@ -8,6 +8,6 @@ namespace byte_lookup(256);
     pol constant sel_bin;
 
     // These two columns are a mapping between instruction tags and their byte lengths
-    // {U8: 1, U16: 2, ... , U128: 16}
-    pol constant table_in_tags; // Column of U8,U16,...,U128
-    pol constant table_byte_lengths; // Columns of byte lengths 1,2,...,16;
+    // {U1: 1, U8: 1, U16: 2, ... , U128: 16}
+    pol constant table_in_tags; // Column of U1,U8,U16,...,U128
+    pol constant table_byte_lengths; // Columns of byte lengths 1,1,2,...,16;

barretenberg/cpp/pil/avm/gadgets/conversion.pil

@@ -17,3 +17,4 @@ namespace conversion(256);
     pol commit input;
     pol commit radix;
     pol commit num_limbs;
+    pol commit output_bits;

barretenberg/cpp/pil/avm/main.pil

@@ -146,7 +146,7 @@ namespace main(256);
     // Helper selector to characterize a Binary chiplet selector
     pol commit sel_bin;
 
-    // Instruction memory tags read/write (1: u8, 2: u16, 3: u32, 4: u64, 5: u128, 6: field)
+    // Instruction memory tags read/write (1: u1, 2: u8, 3: u16, 4: u32, 5: u64, 6: u128, 7: field)
     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.
@@ -311,17 +311,17 @@ namespace main(256);
     //      values should be written into these memory indices.
     //    - For indirect memory accesses, the memory trace constraints ensure that
     //      loaded values come from memory addresses with tag u32. This is enforced in the memory trace
-    //      where each memory entry with flag sel_resolve_ind_addr_x (for x = a,b,c,d) constrains r_int_tag == 3 (u32).
+    //      where each memory entry with flag sel_resolve_ind_addr_x (for x = a,b,c,d) constrains r_int_tag is u32.
     //
     // - ind_addr_a, ind_addr_b, ind_addr_c, ind_addr_d to u32 type: Should be guaranteed by bytecode validation and
     // instruction decomposition as only immediate 32-bit values should be written into the indirect registers.
     //
-    // - 0 <= r_in_tag, w_in_tag <= 6 // This should be constrained by the operation decomposition.
+    // - 0 <= r_in_tag, w_in_tag <= constants.MEM_TAG_FF // This should be constrained by the operation decomposition.
 
     //====== COMPARATOR OPCODES CONSTRAINTS =====================================
-    // Enforce that the tag for the ouput of EQ opcode is u8 (i.e. equal to 1).
-    #[OUTPUT_U8]
-    (sel_op_eq + sel_op_lte + sel_op_lt) * (w_in_tag - 1) = 0;
+    // Enforce that the tag for the ouput of EQ opcode is u1 (i.e. equal to 1).
+    #[OUTPUT_U1]
+    (sel_op_eq + sel_op_lte + sel_op_lt) * (w_in_tag - constants.MEM_TAG_U1) = 0;
 
     //====== FDIV OPCODE CONSTRAINTS ============================================
     // Relation for division over the finite field
@@ -340,13 +340,13 @@ namespace main(256);
     #[SUBOP_FDIV_ZERO_ERR2]
     (sel_op_fdiv + sel_op_div) * op_err * (1 - inv) = 0;
 
-    // Enforcement that instruction tags are FF (tag constant 6).
+    // Enforcement that instruction tags are FF
     // TODO: These 2 conditions might be removed and enforced through
     //       the bytecode decomposition instead.
     #[SUBOP_FDIV_R_IN_TAG_FF]
-    sel_op_fdiv * (r_in_tag - 6) = 0;
+    sel_op_fdiv * (r_in_tag - constants.MEM_TAG_FF) = 0;
     #[SUBOP_FDIV_W_IN_TAG_FF]
-    sel_op_fdiv * (w_in_tag - 6) = 0;
+    sel_op_fdiv * (w_in_tag - constants.MEM_TAG_FF) = 0;
 
     // op_err cannot be maliciously activated for a non-relevant
     // operation selector, i.e., op_err == 1 ==> sel_op_fdiv || sel_op_XXX || ...
@@ -542,9 +542,9 @@ namespace main(256);
     binary.start {binary.clk, binary.acc_ia, binary.acc_ib, binary.acc_ic, binary.op_id, binary.in_tag};
 
     #[PERM_MAIN_CONV]
-    sel_op_radix_le {clk, ia, ic, id}
+    sel_op_radix_le {clk, ia, ib, ic, id}
     is
-    conversion.sel_to_radix_le {conversion.clk, conversion.input, conversion.radix, conversion.num_limbs};
+    conversion.sel_to_radix_le {conversion.clk, conversion.input, conversion.radix, conversion.num_limbs, conversion.output_bits};
 
     // This will be enabled when we migrate just to sha256Compression, as getting sha256 to work with it is tricky.
     // #[PERM_MAIN_SHA256]