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Merged
copybara-service merged 7 commits into from
May 21, 2026
Merged

2/2: Add enumerate() to DSLX stdlib #4022

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f059773
Remove builtin enumerate
joannabrozek Mar 30, 2026
c067314
type_system_v2: Use std::enumerate()
joannabrozek Apr 29, 2026
e10637c
type_system_v2: Allow empty range
joannabrozek Apr 29, 2026
35110ca
std: Add test for struct enumeration
joannabrozek Apr 29, 2026
43afe3f
std: Add support for empty array enumeration
joannabrozek Apr 29, 2026
381b325
deduce_utils: Allow indexing into zero-sized arrays for constexpr
joannabrozek Apr 30, 2026
b3ba97c
type_system_v2: Add empty range tests
joannabrozek May 7, 2026
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18 changes: 0 additions & 18 deletions xls/dslx/bytecode/builtins.cc
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Expand Up @@ -518,24 +518,6 @@ absl::Status RunBuiltinCtz(const Bytecode& bytecode, InterpreterStack& stack) {
return absl::OkStatus();
}

absl::Status RunBuiltinEnumerate(const Bytecode& bytecode,
InterpreterStack& stack) {
XLS_RET_CHECK(!stack.empty());
XLS_ASSIGN_OR_RETURN(InterpValue input, stack.Pop());
XLS_ASSIGN_OR_RETURN(const std::vector<InterpValue>* values,
input.GetValues());

std::vector<InterpValue> elements;
elements.reserve(values->size());
for (int32_t i = 0; i < values->size(); i++) {
elements.push_back(
InterpValue::MakeTuple({InterpValue::MakeU32(i), values->at(i)}));
}
XLS_ASSIGN_OR_RETURN(InterpValue result, InterpValue::MakeArray(elements));
stack.Push(result);
return absl::OkStatus();
}

absl::Status RunBuiltinOrReduce(const Bytecode& bytecode,
InterpreterStack& stack) {
VLOG(3) << "Executing builtin OrReduce.";
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2 changes: 0 additions & 2 deletions xls/dslx/bytecode/builtins.h
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Expand Up @@ -72,8 +72,6 @@ absl::Status RunBuiltinCeilLog2(const Bytecode& bytecode,
absl::Status RunBuiltinClz(const Bytecode& bytecode, InterpreterStack& stack);
absl::Status RunBuiltinCover(const Bytecode& bytecode, InterpreterStack& stack);
absl::Status RunBuiltinCtz(const Bytecode& bytecode, InterpreterStack& stack);
absl::Status RunBuiltinEnumerate(const Bytecode& bytecode,
InterpreterStack& stack);
absl::Status RunBuiltinOrReduce(const Bytecode& bytecode,
InterpreterStack& stack);
absl::Status RunBuiltinRange(const Bytecode& bytecode, InterpreterStack& stack);
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2 changes: 0 additions & 2 deletions xls/dslx/bytecode/bytecode_interpreter.cc
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Expand Up @@ -1673,8 +1673,6 @@ absl::Status BytecodeInterpreter::RunBuiltinFn(const Bytecode& bytecode,
return RunBuiltinCover(bytecode, stack_);
case Builtin::kCtz:
return RunBuiltinCtz(bytecode, stack_);
case Builtin::kEnumerate:
return RunBuiltinEnumerate(bytecode, stack_);
case Builtin::kFail: {
XLS_ASSIGN_OR_RETURN(InterpValue value, Pop());
std::string message{value.ToString()};
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23 changes: 0 additions & 23 deletions xls/dslx/bytecode/bytecode_interpreter_test.cc
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Expand Up @@ -1940,29 +1940,6 @@ fn main(x: s10, y: s10) -> s10 {
EXPECT_THAT(bits.ToInt64(), IsOkAndHolds(-507));
}

TEST_F(BytecodeInterpreterTest, BuiltinEnumerate) {
constexpr std::string_view kProgram = R"(
fn main() -> (u32, u8)[4] {
let x = u8[4]:[5, 6, 7, 8];
enumerate(x)
})";

XLS_ASSERT_OK_AND_ASSIGN(InterpValue actual, Interpret(kProgram, "main"));
XLS_ASSERT_OK_AND_ASSIGN(
InterpValue expected,
InterpValue::MakeArray({
InterpValue::MakeTuple(
{InterpValue::MakeUBits(32, 0), InterpValue::MakeUBits(8, 5)}),
InterpValue::MakeTuple(
{InterpValue::MakeUBits(32, 1), InterpValue::MakeUBits(8, 6)}),
InterpValue::MakeTuple(
{InterpValue::MakeUBits(32, 2), InterpValue::MakeUBits(8, 7)}),
InterpValue::MakeTuple(
{InterpValue::MakeUBits(32, 3), InterpValue::MakeUBits(8, 8)}),
}));
EXPECT_TRUE(expected.Eq(actual));
}

TEST_F(BytecodeInterpreterTest, BuiltinUMulp) {
constexpr std::string_view kProgram = R"(
fn main(x: u10, y: u10) -> u10 {
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1 change: 0 additions & 1 deletion xls/dslx/dslx_builtins.h
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Expand Up @@ -46,7 +46,6 @@ namespace xls::dslx {
X("decode", kDecode) \
X("element_count", kElementCount) \
X("encode", kEncode) \
X("enumerate", kEnumerate) \
X("fail!", kFail) \
X("gate!", kGate) \
X("map", kMap) \
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2 changes: 0 additions & 2 deletions xls/dslx/frontend/builtin_stubs.x
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Expand Up @@ -56,8 +56,6 @@ fn decode<T: type, N: u32>(x: uN[N]) -> T;

fn element_count<T: type>() -> u32;

fn enumerate<T: type, N: u32>(x: T[N]) -> (u32, T)[N];

fn fail!<N: u32, T: type> (label: u8[N], fallback_value: T) -> T;

fn gate!<T: type>(x: u1, y: T) -> T;
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1 change: 0 additions & 1 deletion xls/dslx/frontend/builtins_metadata.cc
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Expand Up @@ -98,7 +98,6 @@ const absl::flat_hash_map<std::string, BuiltinsData>& GetParametricBuiltins() {
{"signex", {}},
{"array_slice", {}},
{"update", {}},
{"enumerate", {}},
{"widening_cast", {}},
{"checked_cast", {}},

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23 changes: 10 additions & 13 deletions xls/dslx/ir_convert/testdata/ir_converter_test_ArrayEnumerate.ir
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Expand Up @@ -3,23 +3,20 @@ package test_module
file_number 0 "xls/dslx/stdlib/std.x"
file_number 1 "test_module.x"

fn ____std__enumerate__4_u8_counted_for_0_body(i: bits[32] id=7, result: (bits[32], bits[8])[4] id=10, x: bits[8][4] id=11) -> (bits[32], bits[8])[4] {
literal.8: bits[32] = literal(value=0, id=8)
add.9: bits[32] = add(i, literal.8, id=9)
array_index.12: bits[8] = array_index(x, indices=[add.9], id=12)
tuple.13: (bits[32], bits[8]) = tuple(add.9, array_index.12, id=13)
ret array_update.14: (bits[32], bits[8])[4] = array_update(result, tuple.13, indices=[add.9], id=14)
fn ____std__enumerate__4_u8_counted_for_0_body(i: bits[32] id=4, result: (bits[32], bits[8])[4] id=7, x: bits[8][4] id=8) -> (bits[32], bits[8])[4] {
literal.5: bits[32] = literal(value=0, id=5)
add.6: bits[32] = add(i, literal.5, id=6)
array_index.9: bits[8] = array_index(x, indices=[add.6], id=9)
tuple.10: (bits[32], bits[8]) = tuple(add.6, array_index.9, id=10)
ret array_update.11: (bits[32], bits[8])[4] = array_update(result, tuple.10, indices=[add.6], id=11)
}

fn __std__enumerate__4_u8(x: bits[8][4] id=1) -> (bits[32], bits[8])[4] {
literal.3: bits[32] = literal(value=0, id=3)
literal.4: bits[8] = literal(value=0, id=4)
tuple.5: (bits[32], bits[8]) = tuple(literal.3, literal.4, id=5)
array.6: (bits[32], bits[8])[4] = array(tuple.5, tuple.5, tuple.5, tuple.5, id=6)
literal.3: (bits[32], bits[8])[4] = literal(value=[(0, 0), (0, 0), (0, 0), (0, 0)], id=3)
N: bits[32] = literal(value=4, id=2)
ret counted_for.15: (bits[32], bits[8])[4] = counted_for(array.6, trip_count=4, stride=1, body=____std__enumerate__4_u8_counted_for_0_body, invariant_args=[x], id=15)
ret counted_for.12: (bits[32], bits[8])[4] = counted_for(literal.3, trip_count=4, stride=1, body=____std__enumerate__4_u8_counted_for_0_body, invariant_args=[x], id=12)
}

top fn __test_module__main(array: bits[8][4] id=16) -> (bits[32], bits[8])[4] {
ret invoke.17: (bits[32], bits[8])[4] = invoke(array, to_apply=__std__enumerate__4_u8, id=17)
top fn __test_module__main(array: bits[8][4] id=13) -> (bits[32], bits[8])[4] {
ret invoke.14: (bits[32], bits[8])[4] = invoke(array, to_apply=__std__enumerate__4_u8, id=14)
}
44 changes: 43 additions & 1 deletion xls/dslx/stdlib/std.x
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Expand Up @@ -19,7 +19,7 @@
pub fn enumerate<T: type, N: u32>(x: T[N]) -> (u32, T)[N] {
for (i, result) in 0..N {
update(result, i, (i, x[i]))
}([(u32:0, zero!<T>()), ...])
}(zero!<(u32, T)[N]>())
}

#[test]
Expand All @@ -32,6 +32,13 @@ fn emumerate_test() {
assert_eq(enumerated[3], (3, 8));
}

#[test]
fn emumerate_empty_array_test() {
let empty_array: u32[0] = [];
let enumerated_empty = enumerate(empty_array);
assert_eq(enumerated_empty, []);
}

#[test]
fn enumerate_type_test() {
type RamData = uN[8];
Expand All @@ -51,6 +58,41 @@ fn enumerate_tuple_test() {
assert_eq(enumerated[1], (1, (false, 2)));
}

type TestIdx = uN[2];
type TestValue = uN[32];

struct TestData { idx: TestIdx, value: TestValue }

const TEST_DATA = TestData[20]:[
TestData { idx: TestIdx:0, value: TestValue:0xca32_9f4a },
TestData { idx: TestIdx:1, value: TestValue:0x0fb3_fa42 },
TestData { idx: TestIdx:2, value: TestValue:0xe7ee_da41 },
TestData { idx: TestIdx:3, value: TestValue:0xef51_f98c },
TestData { idx: TestIdx:0, value: TestValue:0x97a3_a2d2 },
TestData { idx: TestIdx:0, value: TestValue:0xea06_e94b },
TestData { idx: TestIdx:1, value: TestValue:0x5fac_17ce },
TestData { idx: TestIdx:3, value: TestValue:0xf9d8_9938 },
TestData { idx: TestIdx:2, value: TestValue:0xc262_2d2e },
TestData { idx: TestIdx:2, value: TestValue:0xb4dd_424e },
TestData { idx: TestIdx:1, value: TestValue:0x01f9_b9e4 },
TestData { idx: TestIdx:1, value: TestValue:0x3020_6eec },
TestData { idx: TestIdx:3, value: TestValue:0x3124_87b5 },
TestData { idx: TestIdx:0, value: TestValue:0x0a49_f5e3 },
TestData { idx: TestIdx:2, value: TestValue:0xde3b_5d0f },
TestData { idx: TestIdx:3, value: TestValue:0x5948_c1b3 },
TestData { idx: TestIdx:0, value: TestValue:0xa26d_851f },
TestData { idx: TestIdx:3, value: TestValue:0x3fa9_59c0 },
TestData { idx: TestIdx:1, value: TestValue:0x4efd_dd09 },
TestData { idx: TestIdx:1, value: TestValue:0x6d75_058a },
];

#[test]
fn enumerate_struct_test() {
let enumerated = enumerate(TEST_DATA);
assert_eq(enumerated[0], (0, TEST_DATA[0]));
assert_eq(enumerated[19], (19, TEST_DATA[19]));
}

pub fn sizeof<S: bool, N: u32>(x: xN[S][N]) -> u32 { N }

#[test]
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6 changes: 0 additions & 6 deletions xls/dslx/tests/BUILD
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Expand Up @@ -338,12 +338,6 @@ dslx_lang_test(

dslx_lang_test(name = "for_over_range")

dslx_lang_test(
name = "enumerate",
compare = "interpreter",
convert_to_ir = True,
)

dslx_lang_test(
name = "character_conversion",
# TODO: https://github.com/google/xls/issues/1526 - fails opportunistic_postcondition in autofmt
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25 changes: 0 additions & 25 deletions xls/dslx/tests/enumerate.x
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This file was deleted.

9 changes: 0 additions & 9 deletions xls/dslx/tests/errors/error_modules_test.py
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Expand Up @@ -1097,15 +1097,6 @@ def test_user_defined_parametric_type(self):
stderr,
)

def test_match_empty_range(self):
stderr = self._run(
'xls/dslx/tests/errors/match_empty_range.x',
)
self.assertIn(
'`u32:0..u32:0` from `u32:0` to `u32:0` is an empty range',
stderr,
)

def test_parametric_test_fn(self):
stderr = self._run(
'xls/dslx/tests/errors/parametric_test_fn.x',
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21 changes: 0 additions & 21 deletions xls/dslx/tests/errors/match_empty_range.x
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This file was deleted.

22 changes: 10 additions & 12 deletions xls/dslx/type_system/deduce_utils.cc
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Expand Up @@ -239,18 +239,6 @@ absl::Status ValidateArrayIndex(const Index& node, const Type& array_type,
// producing a `Type`.
const auto& casted_array_type = dynamic_cast<const ArrayType&>(array_type);

// Reject indexing into zero-sized arrays regardless of whether the index is
// constexpr, since out-of-bounds semantics (return last element) are
// undefined for empty arrays.

XLS_ASSIGN_OR_RETURN(int64_t concrete_size,
casted_array_type.size().GetAsInt64());
if (concrete_size == 0) {
return TypeInferenceErrorStatus(node.span(), &array_type,
"Zero-sized arrays cannot be indexed",
file_table);
}

if (!ti.IsKnownConstExpr(rhs)) {
return absl::OkStatus();
}
Expand All @@ -270,6 +258,16 @@ absl::Status ValidateArrayIndex(const Index& node, const Type& array_type,
constexpr_index),
file_table);
}

// Reject indexing into zero-sized arrays, since out-of-bounds semantics
// (return last element) are undefined for empty arrays.
XLS_ASSIGN_OR_RETURN(int64_t concrete_size,
casted_array_type.size().GetAsInt64());
if (concrete_size == 0) {
return TypeInferenceErrorStatus(node.span(), &array_type,
"Zero-sized arrays cannot be indexed",
file_table);
}
return absl::OkStatus();
}

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4 changes: 1 addition & 3 deletions xls/dslx/type_system/typecheck_module_test.cc
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Expand Up @@ -118,9 +118,7 @@ fn main() -> u2 { p<u32:1>(u2:0) }

TEST_F(TypecheckV2Test, IndexZeroSizedArray) {
std::string_view text = R"(fn f(a: u8[0], b: u3) -> u8 { a[b] })";
EXPECT_THAT(Typecheck(text),
StatusIs(absl::StatusCode::kInvalidArgument,
HasSubstr("Zero-sized arrays cannot be indexed")));
XLS_EXPECT_OK(Typecheck(text));
}

TEST_F(TypecheckV2Test, ZeroMacroFunctionRefIsNotValue) {
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27 changes: 22 additions & 5 deletions xls/dslx/type_system_v2/typecheck_module_v2_array_tuple_test.cc
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Expand Up @@ -1727,13 +1727,30 @@ const X = foo()..(A * 2);
}

TEST(TypecheckV2Test, RangeExprEmptyRange) {
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@richmckeever richmckeever May 5, 2026

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It seems like here and in other test files, we should keep empty range/array tests but change the assertions to expect success, and add a const_assert! in the DSLX that expects it to be empty.

We should also add tests for an empty range with the start being the max of the type, for both signed and unsigned, because there is some logic which normalizes exclusive ranges by converting them into inclusive with end + 1.

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@joannabrozek joannabrozek May 7, 2026

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I restored RangeExprEmptyRange test and added two more to the same file.

XLS_ASSERT_OK_AND_ASSIGN(TypecheckResult result, TypecheckV2(R"(
EXPECT_THAT(R"(
const A = s8:4;
const X = A..s8:4;
)"));
ASSERT_THAT(result.tm.warnings.warnings().size(), 1);
EXPECT_EQ(result.tm.warnings.warnings()[0].message,
"`A..s8:4` from `s8:4` to `s8:4` is an empty range");
const_assert!(X == []);
)",
TypecheckSucceeds(HasNodeWithType("X", "sN[8]")));
}

TEST(TypecheckV2Test, RangeExprEmptyRangeSignedMax) {
EXPECT_THAT(R"(
const A = s32::MAX;
const X = A..A;
const_assert!(X == []);
)",
TypecheckSucceeds(HasNodeWithType("X", "sN[32]")));
}

TEST(TypecheckV2Test, RangeExprEmptyRangeUnsignedMax) {
EXPECT_THAT(R"(
const A = u32::MAX;
const X = A..A;
const_assert!(X == []);
)",
TypecheckSucceeds(HasNodeWithType("X", "uN[32]")));
}

TEST(TypecheckV2Test, RangeExprSignednessMismatch) {
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15 changes: 0 additions & 15 deletions xls/dslx/type_system_v2/typecheck_module_v2_builtin_test.cc
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Expand Up @@ -659,21 +659,6 @@ const_assert!(element_count<imported::T>() == 10);
XLS_EXPECT_OK(TypecheckV2(kProgram, "main", &import_data));
}

TEST(TypecheckV2BuiltinTest, Enumerate) {
EXPECT_THAT(R"(const Y = enumerate<u16, u32:3>([u16:1, u16:2, u16:3]);)",
TypecheckSucceeds(HasNodeWithType("Y", "(uN[32], uN[16])[3]")));
}

TEST(TypecheckV2BuiltinTest, EnumerateImplicitSize) {
EXPECT_THAT(R"(const Y = enumerate<u16>([u16:1, u16:2, u16:3]);)",
TypecheckSucceeds(HasNodeWithType("Y", "(uN[32], uN[16])[3]")));
}

TEST(TypecheckV2BuiltinTest, EnumerateImplicitType) {
EXPECT_THAT(R"(const Y = enumerate([u16:1, u16:2, u16:3]);)",
TypecheckSucceeds(HasNodeWithType("Y", "(uN[32], uN[16])[3]")));
}

TEST(TypecheckV2BuiltinTest, Fail) {
EXPECT_THAT(
R"(
Expand Down
5 changes: 3 additions & 2 deletions xls/dslx/type_system_v2/typecheck_module_v2_lambda_test.cc
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Expand Up @@ -208,12 +208,13 @@ const_assert!(ARR[1] == u16:2);
TEST(TypecheckV2Test, NestedLambdas) {
EXPECT_THAT(
R"(
import std;
fn main() -> u32[4][5] {
let z = zero!<u32[4][5]>();
map(enumerate(z), | tup | {
map(std::enumerate(z), | tup | {
let i = tup.0;
let arr = tup.1;
map(enumerate(arr), | tup2 | {
map(std::enumerate(arr), | tup2 | {
let j = tup2.0;
i + j
})
Expand Down
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