Module tags 

Shared NaN-boxing tag constants and helpers.

This module is the single source of truth for the NaN-boxing bit layout used by ValueWord in the VM stack. The JIT, GC, and any other subsystem that needs to inspect or construct NaN-boxed values should import constants from here.

NaN-boxing scheme

All tagged values use sign bit = 1 with a quiet NaN exponent, giving us 51 bits for tag + payload. Normal f64 values (including NaN, which is canonicalized to a positive quiet NaN) are stored directly and never collide with our tagged range.

Tagged: 0xFFF[C-F]_XXXX_XXXX_XXXX
  Bit 63    = 1 (sign, marks as tagged)
  Bits 62-52 = 0x7FF (NaN exponent)
  Bit 51    = 1 (quiet NaN bit)
  Bits 50-48 = tag (3 bits)
  Bits 47-0  = payload (48 bits)

Constants

CANONICAL_NAN

Canonical NaN value used when the original f64 is NaN. Positive quiet NaN: 0x7FF8_0000_0000_0000 (sign=0, exponent all 1s, quiet bit). This has sign=0 so it will NOT be detected as tagged (our tagged values have sign=1).

HEAP_KIND_ARRAY

HEAP_KIND_ATOMIC

HEAP_KIND_BIG_INT

HEAP_KIND_BOOL

HEAP_KIND_BOOL_ARRAY

HEAP_KIND_CHANNEL

HEAP_KIND_CHAR

HEAP_KIND_CLOSURE

HEAP_KIND_COLUMN_REF

HEAP_KIND_CONTENT

HEAP_KIND_DATATABLE

HEAP_KIND_DATA_DATETIME_REF

HEAP_KIND_DATA_REFERENCE

HEAP_KIND_DATETIME_EXPR

HEAP_KIND_DECIMAL

HEAP_KIND_DEQUE

HEAP_KIND_DURATION

HEAP_KIND_ENUM

HEAP_KIND_ERR

HEAP_KIND_EXPR_PROXY

HEAP_KIND_F32_ARRAY

HEAP_KIND_FILTER_EXPR

HEAP_KIND_FLOAT_ARRAY

HEAP_KIND_FLOAT_ARRAY_SLICE

HEAP_KIND_FUNCTION

HEAP_KIND_FUNCTION_REF

HEAP_KIND_FUTURE

HEAP_KIND_GENERATOR

HEAP_KIND_HASHMAP

HEAP_KIND_HOST_CLOSURE

HEAP_KIND_I8_ARRAY

HEAP_KIND_I16_ARRAY

HEAP_KIND_I32_ARRAY

HEAP_KIND_INDEXED_TABLE

HEAP_KIND_INSTANT

HEAP_KIND_INT_ARRAY

HEAP_KIND_IO_HANDLE

HEAP_KIND_ITERATOR

HEAP_KIND_LAZY

HEAP_KIND_MATRIX

HEAP_KIND_MODULE_FUNCTION

HEAP_KIND_MUTEX

HEAP_KIND_NATIVE_SCALAR

HEAP_KIND_NATIVE_VIEW

HEAP_KIND_NONE

HEAP_KIND_NUMBER

HEAP_KIND_OK

HEAP_KIND_PRINT_RESULT

HEAP_KIND_PRIORITY_QUEUE

HEAP_KIND_PROJECTED_REF

HEAP_KIND_RANGE

HEAP_KIND_ROW_VIEW

HEAP_KIND_SET

HEAP_KIND_SHARED_CELL

HEAP_KIND_SIMULATION_CALL

HEAP_KIND_SOME

HEAP_KIND_STRING

HEAP_KIND_TASK_GROUP

HEAP_KIND_TIME

HEAP_KIND_TIMEFRAME

HEAP_KIND_TIMESPAN

HEAP_KIND_TIME_REFERENCE

HEAP_KIND_TRAIT_OBJECT

HEAP_KIND_TYPED_OBJECT

HEAP_KIND_TYPED_TABLE

HEAP_KIND_TYPE_ANNOTATED_VALUE

HEAP_KIND_TYPE_ANNOTATION

HEAP_KIND_U8_ARRAY

HEAP_KIND_U16_ARRAY

HEAP_KIND_U32_ARRAY

HEAP_KIND_U64_ARRAY

HEAP_KIND_UNIT

I48_MAX

Maximum i48 value: 2^47 - 1

I48_MIN

Minimum i48 value: -2^47

PAYLOAD_MASK

Mask for extracting the 48-bit payload (bits 0-47).

TAG_BASE

Tagged value base: sign=1 + exponent all 1s + quiet NaN bit. Binary: 1_11111111111_1000…0 = 0xFFF8_0000_0000_0000 All tagged values have this prefix, with the 3-bit tag in bits 50-48.

TAG_BOOL

Inline bool (payload bit 0: 0=false, 1=true).

TAG_FUNCTION

Function reference (payload = u16 function_id).

TAG_HEAP

Heap pointer to Arc<HeapValue> (48-bit pointer in payload).

TAG_INT

Inline i48 (48-bit signed integer, sign-extended to i64).

TAG_MASK

Mask for extracting the 3-bit tag (bits 48-50).

TAG_MODULE_FN

Module function reference (payload = u32 index).

TAG_NONE

None (Option::None / null).

TAG_REF

Reference to a stack slot (payload = absolute slot index).

TAG_SHIFT

Bit shift for the tag field.

TAG_UNIT

Unit (void return value).

Functions

get_payload

Extract the 48-bit payload from a NaN-boxed u64.

get_tag

Extract the 3-bit tag from a tagged NaN-boxed u64.

is_number

Check whether a u64 is a plain f64 (not tagged).

is_tagged

Check whether a u64 is a tagged NaN-boxed value (as opposed to a plain f64).

make_tagged

Build a tagged NaN-boxed u64 from a tag and payload.

sign_extend_i48

Sign-extend a 48-bit value to i64.