std::intrinsics - Rust (original) (raw)

🔬This is a nightly-only experimental API. (core_intrinsics)

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Compiler intrinsics.

The functions in this module are implementation details of core and should not be used outside of the standard library. We generally provide access to intrinsics via stable wrapper functions. Use these instead.

These are the imports making intrinsics available to Rust code. The actual implementations live in the compiler. Some of these intrinsics are lowered to MIR in https://github.com/rust-lang/rust/blob/master/compiler/rustc_mir_transform/src/lower_intrinsics.rs. The remaining intrinsics are implemented for the LLVM backend in https://github.com/rust-lang/rust/blob/master/compiler/rustc_codegen_ssa/src/mir/intrinsic.rsand https://github.com/rust-lang/rust/blob/master/compiler/rustc_codegen_llvm/src/intrinsic.rs, and for const evaluation in https://github.com/rust-lang/rust/blob/master/compiler/rustc_const_eval/src/interpret/intrinsics.rs.

§Const intrinsics

In order to make an intrinsic unstable usable at compile-time, copy the implementation fromhttps://github.com/rust-lang/miri/blob/master/src/intrinsics tohttps://github.com/rust-lang/rust/blob/master/compiler/rustc_const_eval/src/interpret/intrinsics.rsand make the intrinsic declaration below a const fn. This should be done in coordination with wg-const-eval.

If an intrinsic is supposed to be used from a const fn with a rustc_const_stable attribute,#[rustc_intrinsic_const_stable_indirect] needs to be added to the intrinsic. Such a change requires T-lang approval, because it may bake a feature into the language that cannot be replicated in user code without compiler support.

§Volatiles

The volatile intrinsics provide operations intended to act on I/O memory, which are guaranteed to not be reordered by the compiler across other volatile intrinsics. See read_volatileand write_volatile.

§Atomics

The atomic intrinsics provide common atomic operations on machine words, with multiple possible memory orderings. See theatomic types docs for details.

§Unwinding

Rust intrinsics may, in general, unwind. If an intrinsic can never unwind, add the#[rustc_nounwind] attribute so that the compiler can make use of this fact.

However, even for intrinsics that may unwind, rustc assumes that a Rust intrinsics will never initiate a foreign (non-Rust) unwind, and thus for panic=abort we can always assume that these intrinsics cannot unwind.

fallbackExperimental

mirExperimental

Rustc internal tooling for hand-writing MIR.

simdExperimental

SIMD compiler intrinsics.

AtomicOrderingExperimental

A type for atomic ordering parameters for intrinsics. This is a separate type fromatomic::Ordering so that we can make it ConstParamTy and fix the values used here without a risk of leaking that to stable code.

copy⚠Deprecated

This is an accidentally-stable alias to ptr::copy; use that instead.

copy_nonoverlapping⚠Deprecated

This is an accidentally-stable alias to ptr::copy_nonoverlapping; use that instead.

transmute⚠Deprecated

Reinterprets the bits of a value of one type as another type.

write_bytes⚠Deprecated

This is an accidentally-stable alias to ptr::write_bytes; use that instead.

abortExperimental

Aborts the execution of the process.

add_with_overflowExperimental

Performs checked integer addition.

aggregate_raw_ptrExperimental

Lowers in MIR to Rvalue::Aggregate with AggregateKind::RawPtr.

align_ofExperimental

The minimum alignment of a type.

align_of_val⚠Experimental

The required alignment of the referenced value.

arith_offset⚠Experimental

Calculates the offset from a pointer, potentially wrapping.

assert_inhabitedExperimental

A guard for unsafe functions that cannot ever be executed if T is uninhabited: This will statically either panic, or do nothing. It does not guarantee to ever panic, and should only be called if an assertion failure will imply language UB in the following code.

assert_mem_uninitialized_validExperimental

A guard for std::mem::uninitialized. This will statically either panic, or do nothing. It does not guarantee to ever panic, and should only be called if an assertion failure will imply language UB in the following code.

assert_zero_validExperimental

A guard for unsafe functions that cannot ever be executed if T does not permit zero-initialization: This will statically either panic, or do nothing. It does not _guarantee_to ever panic, and should only be called if an assertion failure will imply language UB in the following code.

assume⚠Experimental

Informs the optimizer that a condition is always true. If the condition is false, the behavior is undefined.

atomic_and⚠Experimental

Bitwise and with the current value, returning the previous value.T must be an integer or pointer type.U must be the same as T if that is an integer type, or usize if T is a pointer type.

atomic_cxchg⚠Experimental

Stores a value if the current value is the same as the old value.T must be an integer or pointer type.

atomic_cxchgweak⚠Experimental

Stores a value if the current value is the same as the old value.T must be an integer or pointer type. The comparison may spuriously fail.

atomic_fence⚠Experimental

An atomic fence.

atomic_load⚠Experimental

Loads the current value of the pointer.T must be an integer or pointer type.

atomic_max⚠Experimental

Maximum with the current value using a signed comparison.T must be a signed integer type.

atomic_min⚠Experimental

Minimum with the current value using a signed comparison.T must be a signed integer type.

atomic_nand⚠Experimental

Bitwise nand with the current value, returning the previous value.T must be an integer or pointer type.U must be the same as T if that is an integer type, or usize if T is a pointer type.

atomic_or⚠Experimental

Bitwise or with the current value, returning the previous value.T must be an integer or pointer type.U must be the same as T if that is an integer type, or usize if T is a pointer type.

atomic_singlethreadfence⚠Experimental

An atomic fence for synchronization within a single thread.

atomic_store⚠Experimental

Stores the value at the specified memory location.T must be an integer or pointer type.

atomic_umax⚠Experimental

Maximum with the current value using an unsigned comparison.T must be an unsigned integer type.

atomic_umin⚠Experimental

Minimum with the current value using an unsigned comparison.T must be an unsigned integer type.

atomic_xadd⚠Experimental

Adds to the current value, returning the previous value.T must be an integer or pointer type.U must be the same as T if that is an integer type, or usize if T is a pointer type.

atomic_xchg⚠Experimental

Stores the value at the specified memory location, returning the old value.T must be an integer or pointer type.

atomic_xor⚠Experimental

Bitwise xor with the current value, returning the previous value.T must be an integer or pointer type.U must be the same as T if that is an integer type, or usize if T is a pointer type.

atomic_xsub⚠Experimental

Subtract from the current value, returning the previous value.T must be an integer or pointer type.U must be the same as T if that is an integer type, or usize if T is a pointer type.

autodiffExperimental

Generates the LLVM body for the automatic differentiation of f using Enzyme, with df as the derivative function and args as its arguments.

bitreverseExperimental

Reverses the bits in an integer type T.

black_boxExperimental

See documentation of std::hint::black_box for details.

breakpointExperimental

Executes a breakpoint trap, for inspection by a debugger.

bswapExperimental

Reverses the bytes in an integer type T.

caller_locationExperimental

Gets a reference to a static Location indicating where it was called.

carrying_mul_addExperimental

Performs full-width multiplication and addition with a carry:multiplier * multiplicand + addend + carry.

catch_unwind⚠Experimental

Rust’s “try catch” construct for unwinding. Invokes the function pointer try_fn with the data pointer data, and calls catch_fn if unwinding occurs while try_fn runs. Returns 1 if unwinding occurred and catch_fn was called; returns 0 otherwise.

ceilf16Experimental

Returns the smallest integer greater than or equal to an f16.

ceilf32Experimental

Returns the smallest integer greater than or equal to an f32.

ceilf64Experimental

Returns the smallest integer greater than or equal to an f64.

ceilf128Experimental

Returns the smallest integer greater than or equal to an f128.

cold_pathExperimental

Hints to the compiler that current code path is cold.

compare_bytes⚠Experimental

Lexicographically compare [left, left + bytes) and [right, right + bytes)as unsigned bytes, returning negative if left is less, zero if all the bytes match, or positive if left is greater.

const_allocate⚠Experimental

Allocates a block of memory at compile time. At runtime, just returns a null pointer.

const_deallocate⚠Experimental

Deallocates a memory which allocated by intrinsics::const_allocate at compile time. At runtime, does nothing.

const_eval_selectExperimental

Selects which function to call depending on the context.

const_make_global⚠Experimental

contract_check_ensuresExperimental

Check if the post-condition cond has been met.

contract_check_requiresExperimental

Check if the pre-condition cond has been met.

copysignf16Experimental

Copies the sign from y to x for f16 values.

copysignf32Experimental

Copies the sign from y to x for f32 values.

copysignf64Experimental

Copies the sign from y to x for f64 values.

copysignf128Experimental

Copies the sign from y to x for f128 values.

cosf16Experimental

Returns the cosine of an f16.

cosf32Experimental

Returns the cosine of an f32.

cosf64Experimental

Returns the cosine of an f64.

cosf128Experimental

Returns the cosine of an f128.

ctlzExperimental

Returns the number of leading unset bits (zeroes) in an integer type T.

ctlz_nonzero⚠Experimental

Like ctlz, but extra-unsafe as it returns undef when given an x with value 0.

ctpopExperimental

Returns the number of bits set in an integer type T

cttzExperimental

Returns the number of trailing unset bits (zeroes) in an integer type T.

cttz_nonzero⚠Experimental

Like cttz, but extra-unsafe as it returns undef when given an x with value 0.

discriminant_valueExperimental

Returns the value of the discriminant for the variant in ‘v’; if T has no discriminant, returns 0.

disjoint_bitor⚠Experimental

Combine two values which have no bits in common.

exact_div⚠Experimental

Performs an exact division, resulting in undefined behavior wherex % y != 0 or y == 0 or x == T::MIN && y == -1

exp2f16Experimental

Returns 2 raised to the power of an f16.

exp2f32Experimental

Returns 2 raised to the power of an f32.

exp2f64Experimental

Returns 2 raised to the power of an f64.

exp2f128Experimental

Returns 2 raised to the power of an f128.

expf16Experimental

Returns the exponential of an f16.

expf32Experimental

Returns the exponential of an f32.

expf64Experimental

Returns the exponential of an f64.

expf128Experimental

Returns the exponential of an f128.

fabsf16Experimental

Returns the absolute value of an f16.

fabsf32Experimental

Returns the absolute value of an f32.

fabsf64Experimental

Returns the absolute value of an f64.

fabsf128Experimental

Returns the absolute value of an f128.

fadd_algebraicExperimental

Float addition that allows optimizations based on algebraic rules.

fadd_fast⚠Experimental

Float addition that allows optimizations based on algebraic rules. Requires that inputs and output of the operation are finite, causing UB otherwise.

fdiv_algebraicExperimental

Float division that allows optimizations based on algebraic rules.

fdiv_fast⚠Experimental

Float division that allows optimizations based on algebraic rules. Requires that inputs and output of the operation are finite, causing UB otherwise.

float_to_int_unchecked⚠Experimental

Converts with LLVM’s fptoui/fptosi, which may return undef for values out of range (https://github.com/rust-lang/rust/issues/10184)

floorf16Experimental

Returns the largest integer less than or equal to an f16.

floorf32Experimental

Returns the largest integer less than or equal to an f32.

floorf64Experimental

Returns the largest integer less than or equal to an f64.

floorf128Experimental

Returns the largest integer less than or equal to an f128.

fmaf16Experimental

Returns a * b + c for f16 values.

fmaf32Experimental

Returns a * b + c for f32 values.

fmaf64Experimental

Returns a * b + c for f64 values.

fmaf128Experimental

Returns a * b + c for f128 values.

fmul_algebraicExperimental

Float multiplication that allows optimizations based on algebraic rules.

fmul_fast⚠Experimental

Float multiplication that allows optimizations based on algebraic rules. Requires that inputs and output of the operation are finite, causing UB otherwise.

fmuladdf16Experimental

Returns a * b + c for f16 values, non-deterministically executing either a fused multiply-add or two operations with rounding of the intermediate result.

fmuladdf32Experimental

Returns a * b + c for f32 values, non-deterministically executing either a fused multiply-add or two operations with rounding of the intermediate result.

fmuladdf64Experimental

Returns a * b + c for f64 values, non-deterministically executing either a fused multiply-add or two operations with rounding of the intermediate result.

fmuladdf128Experimental

Returns a * b + c for f128 values, non-deterministically executing either a fused multiply-add or two operations with rounding of the intermediate result.

forgetExperimental

Moves a value out of scope without running drop glue.

frem_algebraicExperimental

Float remainder that allows optimizations based on algebraic rules.

frem_fast⚠Experimental

Float remainder that allows optimizations based on algebraic rules. Requires that inputs and output of the operation are finite, causing UB otherwise.

fsub_algebraicExperimental

Float subtraction that allows optimizations based on algebraic rules.

fsub_fast⚠Experimental

Float subtraction that allows optimizations based on algebraic rules. Requires that inputs and output of the operation are finite, causing UB otherwise.

is_val_statically_knownExperimental

Returns whether the argument’s value is statically known at compile-time.

likelyExperimental

Hints to the compiler that branch condition is likely to be true. Returns the value passed to it.

log2f16Experimental

Returns the base 2 logarithm of an f16.

log2f32Experimental

Returns the base 2 logarithm of an f32.

log2f64Experimental

Returns the base 2 logarithm of an f64.

log2f128Experimental

Returns the base 2 logarithm of an f128.

log10f16Experimental

Returns the base 10 logarithm of an f16.

log10f32Experimental

Returns the base 10 logarithm of an f32.

log10f64Experimental

Returns the base 10 logarithm of an f64.

log10f128Experimental

Returns the base 10 logarithm of an f128.

logf16Experimental

Returns the natural logarithm of an f16.

logf32Experimental

Returns the natural logarithm of an f32.

logf64Experimental

Returns the natural logarithm of an f64.

logf128Experimental

Returns the natural logarithm of an f128.

maximumf16Experimental

Returns the maximum (IEEE 754-2019 maximum) of two f16 values.

maximumf32Experimental

Returns the maximum (IEEE 754-2019 maximum) of two f32 values.

maximumf64Experimental

Returns the maximum (IEEE 754-2019 maximum) of two f64 values.

maximumf128Experimental

Returns the maximum (IEEE 754-2019 maximum) of two f128 values.

maxnumf16Experimental

Returns the maximum (IEEE 754-2008 maxNum) of two f16 values.

maxnumf32Experimental

Returns the maximum (IEEE 754-2008 maxNum) of two f32 values.

maxnumf64Experimental

Returns the maximum (IEEE 754-2008 maxNum) of two f64 values.

maxnumf128Experimental

Returns the maximum (IEEE 754-2008 maxNum) of two f128 values.

minimumf16Experimental

Returns the minimum (IEEE 754-2019 minimum) of two f16 values.

minimumf32Experimental

Returns the minimum (IEEE 754-2019 minimum) of two f32 values.

minimumf64Experimental

Returns the minimum (IEEE 754-2019 minimum) of two f64 values.

minimumf128Experimental

Returns the minimum (IEEE 754-2019 minimum) of two f128 values.

minnumf16Experimental

Returns the minimum (IEEE 754-2008 minNum) of two f16 values.

minnumf32Experimental

Returns the minimum (IEEE 754-2008 minNum) of two f32 values.

minnumf64Experimental

Returns the minimum (IEEE 754-2008 minNum) of two f64 values.

minnumf128Experimental

Returns the minimum (IEEE 754-2008 minNum) of two f128 values.

mul_with_overflowExperimental

Performs checked integer multiplication

needs_dropExperimental

Returns true if the actual type given as T requires drop glue; returns false if the actual type provided for Timplements Copy.

nontemporal_store⚠Experimental

Emits a nontemporal store, which gives a hint to the CPU that the data should not be held in cache. Except for performance, this is fully equivalent to ptr.write(val).

offset⚠Experimental

Calculates the offset from a pointer.

powf16Experimental

Raises an f16 to an f16 power.

powf32Experimental

Raises an f32 to an f32 power.

powf64Experimental

Raises an f64 to an f64 power.

powf128Experimental

Raises an f128 to an f128 power.

powif16Experimental

Raises an f16 to an integer power.

powif32Experimental

Raises an f32 to an integer power.

powif64Experimental

Raises an f64 to an integer power.

powif128Experimental

Raises an f128 to an integer power.

prefetch_read_dataExperimental

The prefetch intrinsic is a hint to the code generator to insert a prefetch instruction for the given address if supported; otherwise, it is a no-op. Prefetches have no effect on the behavior of the program but can change its performance characteristics.

prefetch_read_instructionExperimental

prefetch_write_dataExperimental

prefetch_write_instructionExperimental

ptr_guaranteed_cmpExperimental

See documentation of <*const T>::guaranteed_eq for details. Returns 2 if the result is unknown. Returns 1 if the pointers are guaranteed equal. Returns 0 if the pointers are guaranteed inequal.

ptr_maskExperimental

Masks out bits of the pointer according to a mask.

ptr_metadataExperimental

Lowers in MIR to Rvalue::UnaryOp with UnOp::PtrMetadata.

ptr_offset_from⚠Experimental

See documentation of <*const T>::offset_from for details.

ptr_offset_from_unsigned⚠Experimental

See documentation of <*const T>::offset_from_unsigned for details.

raw_eq⚠Experimental

Determines whether the raw bytes of the two values are equal.

read_via_copy⚠Experimental

This is an implementation detail of crate::ptr::read and should not be used anywhere else. See its comments for why this exists.

rotate_leftExperimental

Performs rotate left.

rotate_rightExperimental

Performs rotate right.

round_ties_even_f16Experimental

Returns the nearest integer to an f16. Rounds half-way cases to the number with an even least significant digit.

round_ties_even_f32Experimental

Returns the nearest integer to an f32. Rounds half-way cases to the number with an even least significant digit.

round_ties_even_f64Experimental

Returns the nearest integer to an f64. Rounds half-way cases to the number with an even least significant digit.

round_ties_even_f128Experimental

Returns the nearest integer to an f128. Rounds half-way cases to the number with an even least significant digit.

roundf16Experimental

Returns the nearest integer to an f16. Rounds half-way cases away from zero.

roundf32Experimental

Returns the nearest integer to an f32. Rounds half-way cases away from zero.

roundf64Experimental

Returns the nearest integer to an f64. Rounds half-way cases away from zero.

roundf128Experimental

Returns the nearest integer to an f128. Rounds half-way cases away from zero.

rustc_peekExperimental

Magic intrinsic that derives its meaning from attributes attached to the function.

saturating_addExperimental

Computes a + b, saturating at numeric bounds.

saturating_subExperimental

Computes a - b, saturating at numeric bounds.

select_unpredictableExperimental

Returns either true_val or false_val depending on condition b with a hint to the compiler that this condition is unlikely to be correctly predicted by a CPU’s branch predictor (e.g. a binary search).

sinf16Experimental

Returns the sine of an f16.

sinf32Experimental

Returns the sine of an f32.

sinf64Experimental

Returns the sine of an f64.

sinf128Experimental

Returns the sine of an f128.

size_ofExperimental

The size of a type in bytes.

size_of_val⚠Experimental

The size of the referenced value in bytes.

slice_get_unchecked⚠Experimental

Projects to the index-th element of slice_ptr, as the same kind of pointer as the slice was provided – so &mut [T] → &mut T, &[T] → &T,*mut [T] → *mut T, or *const [T] → *const T – without a bounds check.

sqrtf16Experimental

Returns the square root of an f16

sqrtf32Experimental

Returns the square root of an f32

sqrtf64Experimental

Returns the square root of an f64

sqrtf128Experimental

Returns the square root of an f128

sub_with_overflowExperimental

Performs checked integer subtraction

three_way_compareExperimental

Does a three-way comparison between the two arguments, which must be of character or integer (signed or unsigned) type.

transmute_unchecked⚠Experimental

Like transmute, but even less checked at compile-time: rather than giving an error for size_of::<Src>() != size_of::<Dst>(), it’sUndefined Behavior at runtime.

truncf16Experimental

Returns the integer part of an f16.

truncf32Experimental

Returns the integer part of an f32.

truncf64Experimental

Returns the integer part of an f64.

truncf128Experimental

Returns the integer part of an f128.

type_idExperimental

Gets an identifier which is globally unique to the specified type. This function will return the same value for a type regardless of whichever crate it is invoked in.

type_id_eqExperimental

Tests (at compile-time) if two crate::any::TypeId instances identify the same type. This is necessary because at const-eval time the actual discriminating data is opaque and cannot be inspected directly.

type_nameExperimental

Gets a static string slice containing the name of a type.

typed_swap_nonoverlapping⚠Experimental

Non-overlapping typed swap of a single value.

ub_checksExperimental

Returns whether we should perform some UB-checking at runtime. This eventually evaluates tocfg!(ub_checks), but behaves different from cfg! when mixing crates built with different flags: if the crate has UB checks enabled or carries the #[rustc_preserve_ub_checks]attribute, evaluation is delayed until monomorphization (or until the call gets inlined into a crate that does not delay evaluation further); otherwise it can happen any time.

unaligned_volatile_load⚠Experimental

Performs a volatile load from the src pointer The pointer is not required to be aligned.

unaligned_volatile_store⚠Experimental

Performs a volatile store to the dst pointer. The pointer is not required to be aligned.

unchecked_add⚠Experimental

Returns the result of an unchecked addition, resulting in undefined behavior when x + y > T::MAX or x + y < T::MIN.

unchecked_div⚠Experimental

Performs an unchecked division, resulting in undefined behavior where y == 0 or x == T::MIN && y == -1

unchecked_funnel_shl⚠Experimental

Funnel Shift left.

unchecked_funnel_shr⚠Experimental

Funnel Shift right.

unchecked_mul⚠Experimental

Returns the result of an unchecked multiplication, resulting in undefined behavior when x * y > T::MAX or x * y < T::MIN.

unchecked_rem⚠Experimental

Returns the remainder of an unchecked division, resulting in undefined behavior when y == 0 or x == T::MIN && y == -1

unchecked_shl⚠Experimental

Performs an unchecked left shift, resulting in undefined behavior wheny < 0 or y >= N, where N is the width of T in bits.

unchecked_shr⚠Experimental

Performs an unchecked right shift, resulting in undefined behavior wheny < 0 or y >= N, where N is the width of T in bits.

unchecked_sub⚠Experimental

Returns the result of an unchecked subtraction, resulting in undefined behavior when x - y > T::MAX or x - y < T::MIN.

unlikelyExperimental

Hints to the compiler that branch condition is likely to be false. Returns the value passed to it.

unreachable⚠Experimental

Informs the optimizer that this point in the code is not reachable, enabling further optimizations.

va_arg⚠Experimental

Loads an argument of type T from the va_list ap and increment the argument ap points to.

va_copy⚠Experimental

Copies the current location of arglist src to the arglist dst.

va_end⚠Experimental

Destroy the arglist ap after initialization with va_start or va_copy.

variant_countExperimental

Returns the number of variants of the type T cast to a usize; if T has no variants, returns 0. Uninhabited variants will be counted.

volatile_copy_memory⚠Experimental

Equivalent to the appropriate llvm.memmove.p0i8.0i8.* intrinsic, with a size of count * size_of::<T>() and an alignment of align_of::<T>().

volatile_copy_nonoverlapping_memory⚠Experimental

Equivalent to the appropriate llvm.memcpy.p0i8.0i8.* intrinsic, with a size of count * size_of::<T>() and an alignment of align_of::<T>().

volatile_load⚠Experimental

Performs a volatile load from the src pointer.

volatile_set_memory⚠Experimental

Equivalent to the appropriate llvm.memset.p0i8.* intrinsic, with a size of count * size_of::<T>() and an alignment of align_of::<T>().

volatile_store⚠Experimental

Performs a volatile store to the dst pointer.

vtable_align⚠Experimental

The intrinsic will return the alignment stored in that vtable.

vtable_size⚠Experimental

The intrinsic will return the size stored in that vtable.

wrapping_addExperimental

Returns (a + b) mod 2N, where N is the width of T in bits.

wrapping_mulExperimental

Returns (a * b) mod 2N, where N is the width of T in bits.

wrapping_subExperimental

Returns (a - b) mod 2N, where N is the width of T in bits.

write_via_move⚠Experimental

This is an implementation detail of crate::ptr::write and should not be used anywhere else. See its comments for why this exists.