We need to support the extern "rust-intrinsics" GCC seems to have something at least pretty similar to a lot of these not 100% about all of them, things like transmute look more custom to rust.

https://github.com/rust-lang/rust/blob/master/library/core/src/intrinsics.rs
https://github.com/rust-lang/rust/blob/master/compiler/rustc_codegen_llvm/src/intrinsic.rs

• atomic_cxchg_relaxed_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_relaxed_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_relaxed_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_acquire_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_acquire_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_acquire_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_release_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_release_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_release_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_acqrel_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_acqrel_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_acqrel_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_seqcst_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_seqcst_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchg_seqcst_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_relaxed_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_relaxed_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_relaxed_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_acquire_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_acquire_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_acquire_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_release_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_release_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_release_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_acqrel_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_acqrel_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_acqrel_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_seqcst_relaxed<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_seqcst_acquire<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_cxchgweak_seqcst_seqcst<T: Copy>(dst: *mut T, old: T, src: T) -> (T, bool);
• atomic_load_seqcst<T: Copy>(src: *const T) -> T;
• atomic_load_acquire<T: Copy>(src: *const T) -> T;
• atomic_load_relaxed<T: Copy>(src: *const T) -> T;
• atomic_load_unordered<T: Copy>(src: *const T) -> T;
• atomic_store_seqcst<T: Copy>(dst: *mut T, val: T);
• atomic_store_release<T: Copy>(dst: *mut T, val: T);
• atomic_store_relaxed<T: Copy>(dst: *mut T, val: T);
• atomic_store_unordered<T: Copy>(dst: *mut T, val: T);
• atomic_xchg_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xchg_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xchg_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xchg_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xchg_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xadd_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xadd_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xadd_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xadd_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xadd_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xsub_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xsub_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xsub_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xsub_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xsub_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_and_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_and_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_and_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_and_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_and_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_nand_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_nand_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_nand_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_nand_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_nand_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_or_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_or_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_or_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_or_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_or_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xor_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xor_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xor_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xor_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_xor_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_max_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_max_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_max_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_max_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_max_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_min_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_min_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_min_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_min_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_min_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umin_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umin_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umin_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umin_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umin_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umax_seqcst<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umax_acquire<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umax_release<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umax_acqrel<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_umax_relaxed<T: Copy>(dst: *mut T, src: T) -> T;
• atomic_fence_seqcst();
• atomic_fence_acquire();
• atomic_fence_release();
• atomic_fence_acqrel();
• atomic_singlethreadfence_seqcst();
• atomic_singlethreadfence_acquire();
• atomic_singlethreadfence_release();
• atomic_singlethreadfence_acqrel();
• prefetch_read_data<T>(data: *const T, locality: i32);
• prefetch_write_data<T>(data: *const T, locality: i32);
• prefetch_read_instruction<T>(data: *const T, locality: i32);
• prefetch_write_instruction<T>(data: *const T, locality: i32);
• rustc_peek<T>(_: T) -> T;
• abort() -> !;
• unreachable() -> !;
• assume(b: bool); Implement assume(b: bool); intrinsic #1561
• likely(b: bool) -> bool;
• unlikely(b: bool) -> bool;
• breakpoint();
• size_of<T>() -> usize;
• min_align_of<T>() -> usize;
• pref_align_of<T>() -> usize;
• size_of_val<T: ?Sized>(_: *const T) -> usize;
• min_align_of_val<T: ?Sized>(_: *const T) -> usize;
• type_name<T: ?Sized>() -> &'static str;
• type_id<T: ?Sized + 'static>() -> u64;
• assert_inhabited<T>();
• assert_zero_valid<T>();
• assert_uninit_valid<T>();
• caller_location() -> &'static crate::panic::Location<'static>;
• forget<T: ?Sized>(_: T);
• transmute<T, U>(e: T) -> U;
• needs_drop<T: ?Sized>() -> bool;
• offset<T>(dst: *const T, offset: isize) -> *const T;
• arith_offset<T>(dst: *const T, offset: isize) -> *const T;
• volatile_copy_nonoverlapping_memory<T>(dst: *mut T, src: *const T, count: usize);
• volatile_copy_memory<T>(dst: *mut T, src: *const T, count: usize);
• volatile_set_memory<T>(dst: *mut T, val: u8, count: usize);
• volatile_load<T>(src: *const T) -> T;
• volatile_store<T>(dst: *mut T, val: T);
• unaligned_volatile_load<T>(src: *const T) -> T;
• unaligned_volatile_store<T>(dst: *mut T, val: T);
• sqrtf32(x: f32) -> f32;
• sqrtf64(x: f64) -> f64;
• powif32(a: f32, x: i32) -> f32;
• powif64(a: f64, x: i32) -> f64;
• sinf32(x: f32) -> f32;
• sinf64(x: f64) -> f64;
• cosf32(x: f32) -> f32;
• cosf64(x: f64) -> f64;
• powf32(a: f32, x: f32) -> f32;
• powf64(a: f64, x: f64) -> f64;
• expf32(x: f32) -> f32;
• expf64(x: f64) -> f64;
• exp2f32(x: f32) -> f32;
• exp2f64(x: f64) -> f64;
• logf32(x: f32) -> f32;
• logf64(x: f64) -> f64;
• log10f32(x: f32) -> f32;
• log10f64(x: f64) -> f64;
• log2f32(x: f32) -> f32;
• log2f64(x: f64) -> f64;
• fmaf32(a: f32, b: f32, c: f32) -> f32;
• fmaf64(a: f64, b: f64, c: f64) -> f64;
• fabsf32(x: f32) -> f32;
• fabsf64(x: f64) -> f64;
• minnumf32(x: f32, y: f32) -> f32;
• minnumf64(x: f64, y: f64) -> f64;
• maxnumf32(x: f32, y: f32) -> f32;
• maxnumf64(x: f64, y: f64) -> f64;
• copysignf32(x: f32, y: f32) -> f32;
• copysignf64(x: f64, y: f64) -> f64;
• floorf32(x: f32) -> f32;
• floorf64(x: f64) -> f64;
• ceilf32(x: f32) -> f32;
• ceilf64(x: f64) -> f64;
• truncf32(x: f32) -> f32;
• truncf64(x: f64) -> f64;
• rintf32(x: f32) -> f32;
• rintf64(x: f64) -> f64;
• nearbyintf32(x: f32) -> f32;
• nearbyintf64(x: f64) -> f64;
• roundf32(x: f32) -> f32;
• roundf64(x: f64) -> f64;
• fadd_fast<T: Copy>(a: T, b: T) -> T;
• fsub_fast<T: Copy>(a: T, b: T) -> T;
• fmul_fast<T: Copy>(a: T, b: T) -> T;
• fdiv_fast<T: Copy>(a: T, b: T) -> T;
• frem_fast<T: Copy>(a: T, b: T) -> T;
• float_to_int_unchecked<Float: Copy, Int: Copy>(value: Float) -> Int;
• ctpop<T: Copy>(x: T) -> T;
• ctlz<T: Copy>(x: T) -> T;
• ctlz_nonzero<T: Copy>(x: T) -> T;
• cttz<T: Copy>(x: T) -> T;
• cttz_nonzero<T: Copy>(x: T) -> T;
• bswap<T: Copy>(x: T) -> T;
• bitreverse<T: Copy>(x: T) -> T;
• add_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
• sub_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
• mul_with_overflow<T: Copy>(x: T, y: T) -> (T, bool);
• exact_div<T: Copy>(x: T, y: T) -> T;
• unchecked_div<T: Copy>(x: T, y: T) -> T;
• unchecked_rem<T: Copy>(x: T, y: T) -> T;
• unchecked_shl<T: Copy>(x: T, y: T) -> T;
• unchecked_shr<T: Copy>(x: T, y: T) -> T;
• unchecked_add<T: Copy>(x: T, y: T) -> T;
• unchecked_sub<T: Copy>(x: T, y: T) -> T;
• unchecked_mul<T: Copy>(x: T, y: T) -> T;
• rotate_left<T: Copy>(x: T, y: T) -> T;
• rotate_right<T: Copy>(x: T, y: T) -> T;
• wrapping_add<T: Copy>(a: T, b: T) -> T;
• wrapping_sub<T: Copy>(a: T, b: T) -> T;
• wrapping_mul<T: Copy>(a: T, b: T) -> T;
• saturating_add<T: Copy>(a: T, b: T) -> T;
• saturating_sub<T: Copy>(a: T, b: T) -> T;
• discriminant_value<T>(v: &T) -> <T as DiscriminantKind>::Discriminant;
• variant_count<T>() -> usize;
• r#try(try_fn: fn(*mut u8), data: *mut u8, catch_fn: fn(*mut u8, *mut u8)) -> i32;
• nontemporal_store<T>(ptr: *mut T, val: T);
• ptr_offset_from<T>(ptr: *const T, base: *const T) -> isize;
• ptr_offset_from_unsigned<T>(ptr: *const T, base: *const T) -> usize;
• ptr_guaranteed_eq<T>(ptr: *const T, other: *const T) -> bool;
• ptr_guaranteed_ne<T>(ptr: *const T, other: *const T) -> bool;
• const_allocate(size: usize, align: usize) -> *mut u8;
• const_deallocate(ptr: *mut u8, size: usize, align: usize);
• raw_eq<T>(a: &T, b: &T) -> bool;
• black_box<T>(dummy: T) -> T; Add black_box intrinsic #3372
• vtable_size(ptr: *const ()) -> usize;
• vtable_align(ptr: *const ()) -> usize;
• copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);