Compiler Intrinsics
The Sway compiler supports a list of intrinsics that perform various low level operations that are useful for building libraries. Compiler intrinsics should rarely be used but are preferred over asm blocks because they are type-checked and safer overall.
Below is a list of all available compiler intrinsics, grouped by category:
Reflection
__is_reference_type<T>() -> bool
Description: Returns true if T is a reference type and false otherwise.
Constraints: None.
__is_str_array<T>() -> bool
Description: Returns true if T is a string array and false otherwise.
Constraints: None.
__assert_is_str_array<T>()
Description: Throws a compile error if type T is not a string array.
Constraints: None.
__to_str_array(s: str) -> str[N]
Description: Converts a string slice s to a string array at compile time.
Constraints: Parameter s must be a string literal.
__size_of<T>() -> u64
Description: Returns the size of type T in bytes.
Constraints: None.
__size_of_val<T>(val: T) -> u64
Description: Returns the size of type T in bytes.
Constraints: None.
__size_of_str_array<T>() -> u64
Description: Returns the length N of the string array if T is a string array str[N], or zero if T is not a string array.
Binary operations
__eq<T>(lhs: T, rhs: T) -> bool
Description: Returns whether lhs and rhs are equal.
Constraints: T is bool, u8, u16, u32, u64, u256, b256, or raw_ptr.
__gt<T>(lhs: T, rhs: T) -> bool
Description: Returns whether lhs is greater than rhs.
Constraints: T is u8, u16, u32, u64, u256, b256.
__lt<T>(lhs: T, rhs: T) -> bool
Description: Returns whether lhs is less than rhs.
Constraints: T is u8, u16, u32, u64, u256, b256.
__add<T>(lhs: T, rhs: T) -> T
Description: Adds lhs and rhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256.
__sub<T>(lhs: T, rhs: T) -> T
Description: Subtracts rhs from lhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256.
__mul<T>(lhs: T, rhs: T) -> T
Description: Multiplies lhs by rhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256.
__div<T>(lhs: T, rhs: T) -> T
Description: Divides lhs by rhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256.
__mod<T>(lhs: T, rhs: T) -> T
Description: Modulo of lhs by rhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256.
__and<T>(lhs: T, rhs: T) -> T
Description: Bitwise AND lhs and rhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256, or b256.
__or<T>(lhs: T, rhs: T) -> T
Description: Bitwise OR lhs and rhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256, or b256.
__xor<T>(lhs: T, rhs: T) -> T
Description: Bitwise XOR lhs and rhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256, or b256.
__rsh<T>(lhs: T, rhs: u64) -> T
Description: Logical right shift of lhs by rhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256, or b256.
__lsh<T>(lhs: T, rhs: u64) -> T
Description: Logical left shift of lhs by rhs.
Constraints: T is an integer type: u8, u16, u32, u64, u256, or b256.
Unary operations
__not(val: T) -> T
Description: Bitwise NOT of val.
Constraints: T is an integer type: u8, u16, u32, u64, u256, or b256.
Blockchain
__log<T>(val: T) where T: AbiEncode
Description: Logs value val.
Constraints: T must implement std::codec::AbiEncode.
__revert(code: u64) -> !
Description: Reverts with error code code.
Constraints: None.
__gtf<T>(index: u64, tx_field_id: u64) -> T
Description: Returns transaction field with ID tx_field_id at index index, if applicable. This is a wrapper around FuelVM's gtf instruction. The resulting field is cast to T.
Constraints: None.
__smo<T>(recipient: b256, data: T, coins: u64)
Description: Sends a message data of arbitrary type T and coins amount of the base asset to address recipient.
Constraints: None.
Memory handling
__addr_of<T>(val: T) -> raw_ptr
Description: Returns the address in memory where val is stored.
Constraints: None.
__alloc<T>(count: u64) -> raw_ptr
Description: Allocates count contiguous elements of T on the heap and returns a pointer to the newly allocated memory.
Constraints None.
__ptr_add(ptr: raw_ptr, offset: u64) -> raw_ptr
Description: Adds offset to the raw value of pointer ptr.
Constraints: None.
__ptr_sub(ptr: raw_ptr, offset: u64) -> raw_ptr
Description: Subtracts offset from the raw value of pointer ptr.
Constraints: None.
__slice<T>(item: &[T; N], start: u64, end: u64) -> &[T]
__slice<T>(item: &[T], start: u64, end: u64) -> &[T]
__slice<T>(item: &mut [T; N], start: u64, end: u64) -> &mut [T]
__slice<T>(item: &mut [T], start: u64, end: u64) -> &mut [T]
Description: Slices an array or another slice.
This intrinsic returns a reference to a slice containing the range of elements inside item.
The mutability of reference is defined by the first parameter's mutability.
Runtime bound checks are not generated, and must be done manually when and where appropriated. Compile-time bound checks are done when possible.
Constraints:
itemis a reference to an array or a slice;- when
startis a literal, it must be smaller thanitemlength; - when
endis a literal, it must be smaller than or equal toitemlength; endmust be greater than or equal tostart.
__elem_at<T>(item: &[T; N], index: u64) -> &T
__elem_at<T>(item: &[T], index: u64) -> &T
__elem_at<T>(item: &mut [T; N], index: u64) -> &mut T
__elem_at<T>(item: &mut [T], index: u64) -> &mut T
Description: Returns a reference to the indexed element.
The mutability of reference is defined by the first parameter's mutability.
Runtime bound checks are not generated, and must be done manually when and where appropriated. Compile-time bound checks are done when possible.
Constraints:
itemis a reference to an array or a slice;- when
indexis a literal, it must be smaller thanitemlength.
Storage
Without dynamic_storage experimental feature enabled
__state_load_word(key: b256) -> u64
Description: Reads and returns a single word from storage at key key. If the storage slot at key key is not set, zero is returned.
Constraints: None.
With dynamic_storage experimental feature enabled
__state_load_word(key: b256, offset: u64) -> u64
Description: Reads and returns a single word from storage at key key and offset (in words) offset. If the storage slot at key key is not set, zero is returned.
Constraints: offset must be a valid word offset inside of the storage slot boundaries. E.g., if the storage slot contains four words, the lowest offset is zero, and the highest is three.
__state_store_word(key: b256, val: u64) -> bool
Description: Stores a single word val into storage at key key. Returns a Boolean describing whether the store slot was previously set.
Constraints: None.
__state_load_quad(key: b256, ptr: raw_ptr, slots: u64) -> bool
Description: Reads slots number of slots (32 bytes each) from storage starting at key key and stores them in memory starting at address ptr. Returns a boolean describing whether all the storage slots were previously set.
Constraints: None.
__state_store_quad(key: b256, ptr: raw_ptr, slots: u64) -> bool
Description: Stores slots number of slots (32 bytes each) starting at address ptr in memory into storage starting at key key. Returns a boolean describing whether the first storage slot was previously set.
Constraints: None.
__state_load_slot(key: b256, ptr: raw_ptr, offset: u64, len: u64) -> bool
Description: Reads len bytes from the storage slot at key key starting at byte offset into memory at address ptr. Returns true if the slot was previously set, false otherwise. If the slot was not previously set, memory is not modified. Maps to the SRDD or SRDI opcode, depending on whether len is a constant that fits in a twelve bit immediate.
Constraints: None.
__state_store_slot(key: b256, ptr: raw_ptr, len: u64)
Description: Writes len bytes starting at address ptr in memory into the storage slot at key key. Maps to the SWRD or SWRI opcode, depending on whether len is a constant that fits in a twelve bit immediate.
Constraints: None.
__state_update_slot(key: b256, ptr: raw_ptr, offset: u64, len: u64)
Description: Updates len bytes at byte offset in the storage slot at key key with data from memory at address ptr. If offset is u64::max(), appends the data after the existing content. Maps to the SUPD or SUPI opcode, depending on whether len is a constant that fits in a twelve bit immediate.
Constraints: None.
__state_clear(key: b256, slots: u64) -> bool
Description: Clears slots number of non-dynamic storage slots (32 bytes each) starting at key key. Returns true if all the storage slots were previously set. Maps to the SCWQ opcode.
If slots is zero, no slots will be cleared, and the return value will always be true.
If the return value is not needed, use __state_clear_slots instead, for it is less gas consuming.
Constraints: None.
__state_clear_slots(key: b256, slots: u64)
Description: Clears slots number of dynamic storage slots starting at key key. Unlike __state_clear, it does not report whether slots were previously set, making it less gas consuming. Maps to the SCLR opcode.
If slots is zero, no slots will be cleared.
Constraints: None.
__state_preload(key: b256) -> u64
Description: Preloads the storage slot at key key and returns the length of the stored data. If the storage slot at key key is not set, zero is returned. Maps to the SPLD opcode.
Constraints: None.
Miscellaneous
__jmp_mem()
Description: Jumps to MEM[$hp].
Constraints: None.
__dbg<T>(value: T) -> T where T: Debug
Description: Automatically calls the Debug's trait fmt method on the passed value, with file, line and column information. The passed value is returned without any modification, allowing __dbg(...) to be used inside of any expression.
The code generated by this intrinsic function varies with the compilation mode. For example:
forc build <- will print everything as expected
forc build --release <- nothing will be printed
To enable code generation even on --release builds, the flag force-dbg-in-release needs to be enabled inside Forc.toml, in the [project] section:
[project]
force-dbg-in-release = true
It is strongly recommended to always remove this flag before publishing binaries as it will not have any effect when running on real nodes and it only increases gas usage.
Constraints: T must implement std::debug::Debug.
__transmute<A, B>(src: A) -> B
Description: Reinterprets the bits of the value src of type A as another type B.
Constraints: A and B must have the exactly same size.
__runtime_mem_id<T>() -> u64
__encoding_mem_id<T>() -> u64
Description: Returns an opaque number that identifies the memory representation of a type. No information is conveyed by this number and it should only be compared for equality.
This number is not guaranteed to be stable on different compiler versions.
__runtime_mem_id represents how the type is represented inside the VM's memory.
__encoding_mem_id represents how the type is encoded. It returns zero when type does not have encoding representation.
Constraints: None.