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feat(avm): add isolated test cases for DIV/FDIV divide by zero #16394

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AztecBot merged 1 commit into from
Aug 16, 2025
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feat(avm): add isolated test cases for DIV/FDIV divide by zero #16394

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61 changes: 32 additions & 29 deletions barretenberg/cpp/src/barretenberg/vm2/constraining/relations/alu.test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -924,39 +924,42 @@ TEST_F(AluDivConstrainingTest, NegativeAluDivByZero)
auto a = MemoryValue::from_tag(MemoryTag::U32, 2);
auto b = MemoryValue::from_tag(MemoryTag::U32, 5);
auto c = a / b;
auto trace = process_div_trace({ a, b, c });
check_all_interactions<AluTraceBuilder>(trace);
check_interaction<ExecutionTraceBuilder, lookup_alu_register_tag_value_settings>(trace);
check_relation<alu>(trace);

// Set b, b_inv to 0...
trace.set(Column::alu_ib, 0, 0);
trace.set(Column::alu_b_inv, 0, 0);
// ...and since we haven't set the error correctly, we expect the below to fail:
EXPECT_THROW_WITH_MESSAGE(check_relation<alu>(trace), "DIV_0_ERR");
// We need to set the div_0_err and...
trace.set(Column::alu_sel_div_0_err, 0, 1);
trace.set(Column::alu_sel_div_no_0_err, 0, 0);
EXPECT_THROW_WITH_MESSAGE(check_relation<alu>(trace), "ERR_CHECK");
// ...the overall sel_err:
trace.set(Column::alu_sel_err, 0, 1);
check_relation<alu>(trace);
for (const bool with_tracegen : { false, true }) {
auto trace = with_tracegen ? process_div_with_tracegen({ a, b, c }) : process_div_trace({ a, b, c });
check_all_interactions<AluTraceBuilder>(trace);
check_interaction<ExecutionTraceBuilder, lookup_alu_register_tag_value_settings>(trace);
check_relation<alu>(trace);

// If we try and have div_0_err on without doing a div, the below should fail:
trace.set(Column::alu_sel_op_div, 0, 0);
trace.set(Column::alu_sel_op_mul, 0, 1);
trace.set(Column::alu_op_id, 0, AVM_EXEC_OP_ID_ALU_MUL);
EXPECT_THROW_WITH_MESSAGE(check_relation<alu>(trace), "DIV_0_ERR");
// Set b, b_inv to 0...
trace.set(Column::alu_ib, 0, 0);
trace.set(Column::alu_b_inv, 0, 0);
// ...and since we haven't set the error correctly, we expect the below to fail:
EXPECT_THROW_WITH_MESSAGE(check_relation<alu>(trace), "DIV_0_ERR");
// We need to set the div_0_err and...
trace.set(Column::alu_sel_div_0_err, 0, 1);
trace.set(Column::alu_sel_div_no_0_err, 0, 0);
EXPECT_THROW_WITH_MESSAGE(check_relation<alu>(trace), "ERR_CHECK");
// ...the overall sel_err:
trace.set(Column::alu_sel_err, 0, 1);
check_relation<alu>(trace);

trace.set(Column::alu_sel_op_div, 0, 1);
trace.set(Column::alu_sel_op_mul, 0, 0);
trace.set(Column::alu_op_id, 0, AVM_EXEC_OP_ID_ALU_DIV);
check_relation<alu>(trace);
// If we try and have div_0_err on without doing a div, the below should fail:
trace.set(Column::alu_sel_op_div, 0, 0);
trace.set(Column::alu_sel_op_mul, 0, 1);
trace.set(Column::alu_op_id, 0, AVM_EXEC_OP_ID_ALU_MUL);
EXPECT_THROW_WITH_MESSAGE(check_relation<alu>(trace), "DIV_0_ERR");

// If we try and set b != 0 with div_0_err on, the below should fail:
trace.set(Column::alu_ib, 0, b);
trace.set(Column::alu_b_inv, 0, b.as_ff().invert());
EXPECT_THROW_WITH_MESSAGE(check_relation<alu>(trace), "DIV_0_ERR");
trace.set(Column::alu_sel_op_div, 0, 1);
trace.set(Column::alu_sel_op_mul, 0, 0);
trace.set(Column::alu_op_id, 0, AVM_EXEC_OP_ID_ALU_DIV);
check_relation<alu>(trace);

// If we try and set b != 0 with div_0_err on, the below should fail:
trace.set(Column::alu_ib, 0, b);
trace.set(Column::alu_b_inv, 0, b.as_ff().invert());
EXPECT_THROW_WITH_MESSAGE(check_relation<alu>(trace), "DIV_0_ERR");
}
}

TEST_F(AluDivConstrainingTest, NegativeAluDivFF)
Expand Down
73 changes: 73 additions & 0 deletions barretenberg/cpp/src/barretenberg/vm2/tracegen/alu_trace.test.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -632,6 +632,47 @@ TEST_F(AluTraceGenerationTest, TraceGenerationDivTagError)
FF(static_cast<uint8_t>(MemoryTag::FF) - static_cast<uint8_t>(MemoryTag::U128)).invert()))));
}

TEST_F(AluTraceGenerationTest, TraceGenerationDivByZeroError)
{
builder.process(
{
{ .operation = AluOperation::DIV,
.a = MemoryValue::from<uint64_t>(6),
.b = MemoryValue::from<uint64_t>(0), // c is optional
.error = AluError::DIV_0_ERROR },
},
trace);

auto tag = static_cast<uint8_t>(MemoryTag::U64);

EXPECT_THAT(
trace.as_rows(),
ElementsAre(AllOf(
ROW_FIELD_EQ(alu_sel_op_div, 1),
ROW_FIELD_EQ(alu_sel, 1),
ROW_FIELD_EQ(alu_op_id, AVM_EXEC_OP_ID_ALU_DIV),
ROW_FIELD_EQ(alu_ia, 6),
ROW_FIELD_EQ(alu_ib, 0),
ROW_FIELD_EQ(alu_helper1, 0),
ROW_FIELD_EQ(alu_ia_tag, tag),
ROW_FIELD_EQ(alu_ib_tag, tag),
ROW_FIELD_EQ(alu_max_bits, get_tag_bits(MemoryTag::U64)),
ROW_FIELD_EQ(alu_max_value, get_tag_max_value(MemoryTag::U64)),
ROW_FIELD_EQ(alu_constant_64, 64),
ROW_FIELD_EQ(alu_sel_is_u128, 0),
ROW_FIELD_EQ(alu_tag_u128_diff_inv,
FF(static_cast<uint8_t>(MemoryTag::U64) - static_cast<uint8_t>(MemoryTag::U128)).invert()),
ROW_FIELD_EQ(alu_sel_is_ff, 0),
ROW_FIELD_EQ(alu_tag_ff_diff_inv,
FF(static_cast<uint8_t>(MemoryTag::U64) - static_cast<uint8_t>(MemoryTag::FF)).invert()),
ROW_FIELD_EQ(alu_sel_mul_div_u128, 0),
ROW_FIELD_EQ(alu_sel_div_no_0_err, 0),
ROW_FIELD_EQ(alu_sel_div_0_err, 1),
ROW_FIELD_EQ(alu_sel_tag_err, 0),
ROW_FIELD_EQ(alu_sel_err, 1),
ROW_FIELD_EQ(alu_ab_tags_diff_inv, 0))));
}

// FDIV TESTS

// Note: The test framework below converts all inputs to FF values to allow for many happy path tests without adding
Expand Down Expand Up @@ -766,6 +807,38 @@ TEST_F(AluTraceGenerationTest, TraceGenerationFDivTagError)
FF(FF(u64_tag) - FF(static_cast<uint8_t>(MemoryTag::FF))).invert()))));
}

TEST_F(AluTraceGenerationTest, TraceGenerationFDivByZeroError)
{
builder.process(
{
{ .operation = AluOperation::FDIV,
.a = MemoryValue::from<FF>(6),
.b = MemoryValue::from<FF>(0), // c is optional
.error = AluError::DIV_0_ERROR },
},
trace);

auto tag = static_cast<uint8_t>(MemoryTag::FF);

EXPECT_THAT(trace.as_rows(),
ElementsAre(AllOf(ROW_FIELD_EQ(alu_sel_op_fdiv, 1),
ROW_FIELD_EQ(alu_sel, 1),
ROW_FIELD_EQ(alu_op_id, AVM_EXEC_OP_ID_ALU_FDIV),
ROW_FIELD_EQ(alu_ia, 6),
ROW_FIELD_EQ(alu_ib, 0),
ROW_FIELD_EQ(alu_ia_tag, tag),
ROW_FIELD_EQ(alu_ib_tag, tag),
ROW_FIELD_EQ(alu_max_bits, get_tag_bits(MemoryTag::FF)),
ROW_FIELD_EQ(alu_max_value, get_tag_max_value(MemoryTag::FF)),
ROW_FIELD_EQ(alu_sel_is_u128, 0),
ROW_FIELD_EQ(alu_sel_is_ff, 1),
ROW_FIELD_EQ(alu_tag_ff_diff_inv, 0),
ROW_FIELD_EQ(alu_sel_div_0_err, 1),
ROW_FIELD_EQ(alu_sel_tag_err, 0),
ROW_FIELD_EQ(alu_sel_err, 1),
ROW_FIELD_EQ(alu_ab_tags_diff_inv, 0))));
}

// EQ TESTS

const std::vector<MemoryValue> TEST_VALUES_EQ_OUT = {
Expand Down
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