diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs index 5ec6cb6c71054..1420e00b47ffa 100644 --- a/src/libcore/intrinsics.rs +++ b/src/libcore/intrinsics.rs @@ -1463,38 +1463,8 @@ extern "rust-intrinsic" { /// source as well as std's catch implementation. pub fn try(f: fn(*mut u8), data: *mut u8, local_ptr: *mut u8) -> i32; - /// Computes the byte offset that needs to be applied to `ptr` in order to - /// make it aligned to `align`. - /// If it is not possible to align `ptr`, the implementation returns - /// `usize::max_value()`. - /// - /// There are no guarantees whatsover that offsetting the pointer will not - /// overflow or go beyond the allocation that `ptr` points into. - /// It is up to the caller to ensure that the returned offset is correct - /// in all terms other than alignment. - /// - /// # Examples - /// - /// Accessing adjacent `u8` as `u16` - /// - /// ``` - /// # #![feature(core_intrinsics)] - /// # fn foo(n: usize) { - /// # use std::intrinsics::align_offset; - /// # use std::mem::align_of; - /// # unsafe { - /// let x = [5u8, 6u8, 7u8, 8u8, 9u8]; - /// let ptr = &x[n] as *const u8; - /// let offset = align_offset(ptr as *const (), align_of::()); - /// if offset < x.len() - n - 1 { - /// let u16_ptr = ptr.offset(offset as isize) as *const u16; - /// assert_ne!(*u16_ptr, 500); - /// } else { - /// // while the pointer can be aligned via `offset`, it would point - /// // outside the allocation - /// } - /// # } } - /// ``` + #[cfg(stage0)] + /// docs my friends, its friday! pub fn align_offset(ptr: *const (), align: usize) -> usize; /// Emits a `!nontemporal` store according to LLVM (see their docs). diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs index 63bcc02402015..e2286d23e3348 100644 --- a/src/libcore/ptr.rs +++ b/src/libcore/ptr.rs @@ -1433,15 +1433,22 @@ impl *const T { copy_nonoverlapping(self, dest, count) } - /// Computes the byte offset that needs to be applied in order to - /// make the pointer aligned to `align`. + /// Computes the offset that needs to be applied to the pointer in order to make it aligned to + /// `align`. + /// /// If it is not possible to align the pointer, the implementation returns /// `usize::max_value()`. /// - /// There are no guarantees whatsover that offsetting the pointer will not - /// overflow or go beyond the allocation that the pointer points into. - /// It is up to the caller to ensure that the returned offset is correct - /// in all terms other than alignment. + /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be + /// used with the `offset` or `offset_to` methods. + /// + /// There are no guarantees whatsover that offsetting the pointer will not overflow or go + /// beyond the allocation that the pointer points into. It is up to the caller to ensure that + /// the returned offset is correct in all terms other than alignment. + /// + /// # Panics + /// + /// The function panics if `align` is not a power-of-two. /// /// # Examples /// @@ -1465,13 +1472,30 @@ impl *const T { /// # } } /// ``` #[unstable(feature = "align_offset", issue = "44488")] - pub fn align_offset(self, align: usize) -> usize { + #[cfg(not(stage0))] + pub fn align_offset(self, align: usize) -> usize where T: Sized { + if !align.is_power_of_two() { + panic!("align_offset: align is not a power-of-two"); + } + unsafe { + align_offset(self, align) + } + } + + /// definitely docs. + #[unstable(feature = "align_offset", issue = "44488")] + #[cfg(stage0)] + pub fn align_offset(self, align: usize) -> usize where T: Sized { + if !align.is_power_of_two() { + panic!("align_offset: align is not a power-of-two"); + } unsafe { - intrinsics::align_offset(self as *const _, align) + intrinsics::align_offset(self as *const (), align) } } } + #[lang = "mut_ptr"] impl *mut T { /// Returns `true` if the pointer is null. @@ -1804,44 +1828,6 @@ impl *mut T { (self as *const T).wrapping_offset_from(origin) } - /// Computes the byte offset that needs to be applied in order to - /// make the pointer aligned to `align`. - /// If it is not possible to align the pointer, the implementation returns - /// `usize::max_value()`. - /// - /// There are no guarantees whatsover that offsetting the pointer will not - /// overflow or go beyond the allocation that the pointer points into. - /// It is up to the caller to ensure that the returned offset is correct - /// in all terms other than alignment. - /// - /// # Examples - /// - /// Accessing adjacent `u8` as `u16` - /// - /// ``` - /// # #![feature(align_offset)] - /// # fn foo(n: usize) { - /// # use std::mem::align_of; - /// # unsafe { - /// let x = [5u8, 6u8, 7u8, 8u8, 9u8]; - /// let ptr = &x[n] as *const u8; - /// let offset = ptr.align_offset(align_of::()); - /// if offset < x.len() - n - 1 { - /// let u16_ptr = ptr.offset(offset as isize) as *const u16; - /// assert_ne!(*u16_ptr, 500); - /// } else { - /// // while the pointer can be aligned via `offset`, it would point - /// // outside the allocation - /// } - /// # } } - /// ``` - #[unstable(feature = "align_offset", issue = "44488")] - pub fn align_offset(self, align: usize) -> usize { - unsafe { - intrinsics::align_offset(self as *const _, align) - } - } - /// Calculates the offset from a pointer (convenience for `.offset(count as isize)`). /// /// `count` is in units of T; e.g. a `count` of 3 represents a pointer @@ -2511,8 +2497,200 @@ impl *mut T { { swap(self, with) } + + /// Computes the offset that needs to be applied to the pointer in order to make it aligned to + /// `align`. + /// + /// If it is not possible to align the pointer, the implementation returns + /// `usize::max_value()`. + /// + /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be + /// used with the `offset` or `offset_to` methods. + /// + /// There are no guarantees whatsover that offsetting the pointer will not overflow or go + /// beyond the allocation that the pointer points into. It is up to the caller to ensure that + /// the returned offset is correct in all terms other than alignment. + /// + /// # Panics + /// + /// The function panics if `align` is not a power-of-two. + /// + /// # Examples + /// + /// Accessing adjacent `u8` as `u16` + /// + /// ``` + /// # #![feature(align_offset)] + /// # fn foo(n: usize) { + /// # use std::mem::align_of; + /// # unsafe { + /// let x = [5u8, 6u8, 7u8, 8u8, 9u8]; + /// let ptr = &x[n] as *const u8; + /// let offset = ptr.align_offset(align_of::()); + /// if offset < x.len() - n - 1 { + /// let u16_ptr = ptr.offset(offset as isize) as *const u16; + /// assert_ne!(*u16_ptr, 500); + /// } else { + /// // while the pointer can be aligned via `offset`, it would point + /// // outside the allocation + /// } + /// # } } + /// ``` + #[unstable(feature = "align_offset", issue = "44488")] + #[cfg(not(stage0))] + pub fn align_offset(self, align: usize) -> usize where T: Sized { + if !align.is_power_of_two() { + panic!("align_offset: align is not a power-of-two"); + } + unsafe { + align_offset(self, align) + } + } + + /// definitely docs. + #[unstable(feature = "align_offset", issue = "44488")] + #[cfg(stage0)] + pub fn align_offset(self, align: usize) -> usize where T: Sized { + if !align.is_power_of_two() { + panic!("align_offset: align is not a power-of-two"); + } + unsafe { + intrinsics::align_offset(self as *const (), align) + } + } +} + +/// Align pointer `p`. +/// +/// Calculate offset (in terms of elements of `stride` stride) that has to be applied +/// to pointer `p` so that pointer `p` would get aligned to `a`. +/// +/// Note: This implementation has been carefully tailored to not panic. It is UB for this to panic. +/// The only real change that can be made here is change of `INV_TABLE_MOD_16` and associated +/// constants. +/// +/// If we ever decide to make it possible to call the intrinsic with `a` that is not a +/// power-of-two, it will probably be more prudent to just change to a naive implementation rather +/// than trying to adapt this to accomodate that change. +/// +/// Any questions go to @nagisa. +#[lang="align_offset"] +#[cfg(not(stage0))] +pub(crate) unsafe fn align_offset(p: *const T, a: usize) -> usize { + /// Calculate multiplicative modular inverse of `x` modulo `m`. + /// + /// This implementation is tailored for align_offset and has following preconditions: + /// + /// * `m` is a power-of-two; + /// * `x < m`; (if `x ≥ m`, pass in `x % m` instead) + /// + /// Implementation of this function shall not panic. Ever. + #[inline] + fn mod_inv(x: usize, m: usize) -> usize { + /// Multiplicative modular inverse table modulo 2⁴ = 16. + /// + /// Note, that this table does not contain values where inverse does not exist (i.e. for + /// `0⁻¹ mod 16`, `2⁻¹ mod 16`, etc.) + const INV_TABLE_MOD_16: [usize; 8] = [1, 11, 13, 7, 9, 3, 5, 15]; + /// Modulo for which the `INV_TABLE_MOD_16` is intended. + const INV_TABLE_MOD: usize = 16; + /// INV_TABLE_MOD² + const INV_TABLE_MOD_SQUARED: usize = INV_TABLE_MOD * INV_TABLE_MOD; + + let table_inverse = INV_TABLE_MOD_16[(x & (INV_TABLE_MOD - 1)) >> 1]; + if m <= INV_TABLE_MOD { + return table_inverse & (m - 1); + } else { + // We iterate "up" using the following formula: + // + // $$ xy ≡ 1 (mod 2ⁿ) → xy (2 - xy) ≡ 1 (mod 2²ⁿ) $$ + // + // until 2²ⁿ ≥ m. Then we can reduce to our desired `m` by taking the result `mod m`. + let mut inverse = table_inverse; + let mut going_mod = INV_TABLE_MOD_SQUARED; + loop { + // y = y * (2 - xy) mod n + // + // Note, that we use wrapping operations here intentionally – the original formula + // uses e.g. subtraction `mod n`. It is entirely fine to do them `mod + // usize::max_value()` instead, because we take the result `mod n` at the end + // anyway. + inverse = inverse.wrapping_mul( + 2usize.wrapping_sub(x.wrapping_mul(inverse)) + ) & (going_mod - 1); + if going_mod > m { + return inverse & (m - 1); + } + going_mod = going_mod.wrapping_mul(going_mod); + } + } + } + + let stride = ::mem::size_of::(); + let a_minus_one = a.wrapping_sub(1); + let pmoda = p as usize & a_minus_one; + + if pmoda == 0 { + // Already aligned. Yay! + return 0; + } + + if stride <= 1 { + return if stride == 0 { + // If the pointer is not aligned, and the element is zero-sized, then no amount of + // elements will ever align the pointer. + !0 + } else { + a.wrapping_sub(pmoda) + }; + } + + let smoda = stride & a_minus_one; + // a is power-of-two so cannot be 0. stride = 0 is handled above. + let gcdpow = intrinsics::cttz_nonzero(stride).min(intrinsics::cttz_nonzero(a)); + let gcd = 1usize << gcdpow; + + if gcd == 1 { + // This branch solves for the variable $o$ in following linear congruence equation: + // + // ⎰ p + o ≡ 0 (mod a) # $p + o$ must be aligned to specified alignment $a$ + // ⎱ o ≡ 0 (mod s) # offset $o$ must be a multiple of stride $s$ + // + // where + // + // * a, s are co-prime + // + // This gives us the formula below: + // + // o = (a - (p mod a)) * (s⁻¹ mod a) * s + // + // The first term is “the relative alignment of p to a”, the second term is “how does + // incrementing p by one s change the relative alignment of p”, the third term is + // translating change in units of s to a byte count. + // + // Furthermore, the result produced by this solution is not “minimal”, so it is necessary + // to take the result $o mod lcm(s, a)$. Since $s$ and $a$ are co-prime (i.e. $gcd(s, a) = + // 1$) and $lcm(s, a) = s * a / gcd(s, a)$, we can replace $lcm(s, a)$ with just a $s * a$. + // + // (Author note: we decided later on to express the offset in "elements" rather than bytes, + // which drops the multiplication by `s` on both sides of the modulo.) + return intrinsics::unchecked_rem(a.wrapping_sub(pmoda).wrapping_mul(mod_inv(smoda, a)), a); + } + + if p as usize & (gcd - 1) == 0 { + // This can be aligned, but `a` and `stride` are not co-prime, so a somewhat adapted + // formula is used. + let j = a.wrapping_sub(pmoda) >> gcdpow; + let k = smoda >> gcdpow; + return intrinsics::unchecked_rem(j.wrapping_mul(mod_inv(k, a)), a >> gcdpow); + } + + // Cannot be aligned at all. + return usize::max_value(); } + + // Equality for pointers #[stable(feature = "rust1", since = "1.0.0")] impl PartialEq for *const T { diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs index 82891b691dc57..fdc9aa473e8b8 100644 --- a/src/libcore/slice/mod.rs +++ b/src/libcore/slice/mod.rs @@ -1696,6 +1696,173 @@ impl [T] { self.as_mut_ptr(), other.as_mut_ptr(), self.len()); } } + + /// Function to calculate lenghts of the middle and trailing slice for `align_to{,_mut}`. + fn align_to_offsets(&self) -> (usize, usize) { + // What we gonna do about `rest` is figure out what multiple of `U`s we can put in a + // lowest number of `T`s. And how many `T`s we need for each such "multiple". + // + // Consider for example T=u8 U=u16. Then we can put 1 U in 2 Ts. Simple. Now, consider + // for example a case where size_of:: = 16, size_of:: = 24. We can put 2 Us in + // place of every 3 Ts in the `rest` slice. A bit more complicated. + // + // Formula to calculate this is: + // + // Us = lcm(size_of::, size_of::) / size_of:: + // Ts = lcm(size_of::, size_of::) / size_of:: + // + // Expanded and simplified: + // + // Us = size_of:: / gcd(size_of::, size_of::) + // Ts = size_of:: / gcd(size_of::, size_of::) + // + // Luckily since all this is constant-evaluated... performance here matters not! + #[inline] + fn gcd(a: usize, b: usize) -> usize { + // iterative stein’s algorithm + // We should still make this `const fn` (and revert to recursive algorithm if we do) + // because relying on llvm to consteval all this is… well, it makes me + let (ctz_a, mut ctz_b) = unsafe { + if a == 0 { return b; } + if b == 0 { return a; } + (::intrinsics::cttz_nonzero(a), ::intrinsics::cttz_nonzero(b)) + }; + let k = ctz_a.min(ctz_b); + let mut a = a >> ctz_a; + let mut b = b; + loop { + // remove all factors of 2 from b + b >>= ctz_b; + if a > b { + ::mem::swap(&mut a, &mut b); + } + b = b - a; + unsafe { + if b == 0 { + break; + } + ctz_b = ::intrinsics::cttz_nonzero(b); + } + } + return a << k; + } + let gcd: usize = gcd(::mem::size_of::(), ::mem::size_of::()); + let ts: usize = ::mem::size_of::() / gcd; + let us: usize = ::mem::size_of::() / gcd; + + // Armed with this knowledge, we can find how many `U`s we can fit! + let us_len = self.len() / ts * us; + // And how many `T`s will be in the trailing slice! + let ts_len = self.len() % ts; + return (us_len, ts_len); + } + + /// Transmute the slice to a slice of another type, ensuring aligment of the types is + /// maintained. + /// + /// This method splits the slice into three distinct slices: prefix, correctly aligned middle + /// slice of a new type, and the suffix slice. The middle slice will have the greatest length + /// possible for a given type and input slice. + /// + /// This method has no purpose when either input element `T` or output element `U` are + /// zero-sized and will return the original slice without splitting anything. + /// + /// # Unsafety + /// + /// This method is essentially a `transmute` with respect to the elements in the returned + /// middle slice, so all the usual caveats pertaining to `transmute::` also apply here. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// # #![feature(slice_align_to)] + /// unsafe { + /// let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7]; + /// let (prefix, shorts, suffix) = bytes.align_to::(); + /// // less_efficient_algorithm_for_bytes(prefix); + /// // more_efficient_algorithm_for_aligned_shorts(shorts); + /// // less_efficient_algorithm_for_bytes(suffix); + /// } + /// ``` + #[unstable(feature = "slice_align_to", issue = "44488")] + #[cfg(not(stage0))] + pub unsafe fn align_to(&self) -> (&[T], &[U], &[T]) { + // Note that most of this function will be constant-evaluated, + if ::mem::size_of::() == 0 || ::mem::size_of::() == 0 { + // handle ZSTs specially, which is – don't handle them at all. + return (self, &[], &[]); + } + + // First, find at what point do we split between the first and 2nd slice. Easy with + // ptr.align_offset. + let ptr = self.as_ptr(); + let offset = ::ptr::align_offset(ptr, ::mem::align_of::()); + if offset > self.len() { + return (self, &[], &[]); + } else { + let (left, rest) = self.split_at(offset); + let (us_len, ts_len) = rest.align_to_offsets::(); + return (left, + from_raw_parts(rest.as_ptr() as *const U, us_len), + from_raw_parts(rest.as_ptr().offset((rest.len() - ts_len) as isize), ts_len)) + } + } + + /// Transmute the slice to a slice of another type, ensuring aligment of the types is + /// maintained. + /// + /// This method splits the slice into three distinct slices: prefix, correctly aligned middle + /// slice of a new type, and the suffix slice. The middle slice will have the greatest length + /// possible for a given type and input slice. + /// + /// This method has no purpose when either input element `T` or output element `U` are + /// zero-sized and will return the original slice without splitting anything. + /// + /// # Unsafety + /// + /// This method is essentially a `transmute` with respect to the elements in the returned + /// middle slice, so all the usual caveats pertaining to `transmute::` also apply here. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// # #![feature(slice_align_to)] + /// unsafe { + /// let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7]; + /// let (prefix, shorts, suffix) = bytes.align_to_mut::(); + /// // less_efficient_algorithm_for_bytes(prefix); + /// // more_efficient_algorithm_for_aligned_shorts(shorts); + /// // less_efficient_algorithm_for_bytes(suffix); + /// } + /// ``` + #[unstable(feature = "slice_align_to", issue = "44488")] + #[cfg(not(stage0))] + pub unsafe fn align_to_mut(&mut self) -> (&mut [T], &mut [U], &mut [T]) { + // Note that most of this function will be constant-evaluated, + if ::mem::size_of::() == 0 || ::mem::size_of::() == 0 { + // handle ZSTs specially, which is – don't handle them at all. + return (self, &mut [], &mut []); + } + + // First, find at what point do we split between the first and 2nd slice. Easy with + // ptr.align_offset. + let ptr = self.as_ptr(); + let offset = ::ptr::align_offset(ptr, ::mem::align_of::()); + if offset > self.len() { + return (self, &mut [], &mut []); + } else { + let (left, rest) = self.split_at_mut(offset); + let (us_len, ts_len) = rest.align_to_offsets::(); + let mut_ptr = rest.as_mut_ptr(); + return (left, + from_raw_parts_mut(mut_ptr as *mut U, us_len), + from_raw_parts_mut(mut_ptr.offset((rest.len() - ts_len) as isize), ts_len)) + } + } } #[lang = "slice_u8"] diff --git a/src/libcore/tests/lib.rs b/src/libcore/tests/lib.rs index 8c481338945ff..dbd26b2c71836 100644 --- a/src/libcore/tests/lib.rs +++ b/src/libcore/tests/lib.rs @@ -41,6 +41,8 @@ #![feature(try_from)] #![feature(try_trait)] #![feature(exact_chunks)] +#![feature(slice_align_to)] +#![feature(align_offset)] #![feature(reverse_bits)] #![feature(inclusive_range_methods)] #![feature(iterator_find_map)] diff --git a/src/libcore/tests/ptr.rs b/src/libcore/tests/ptr.rs index 00f87336f3c80..31bc1d677686a 100644 --- a/src/libcore/tests/ptr.rs +++ b/src/libcore/tests/ptr.rs @@ -296,3 +296,92 @@ fn write_unaligned_drop() { } DROPS.with(|d| assert_eq!(*d.borrow(), [0])); } + +#[test] +fn align_offset_zst() { + // For pointers of stride = 0, the pointer is already aligned or it cannot be aligned at + // all, because no amount of elements will align the pointer. + let mut p = 1; + while p < 1024 { + assert_eq!((p as *const ()).align_offset(p), 0); + if p != 1 { + assert_eq!(((p + 1) as *const ()).align_offset(p), !0); + } + p = (p + 1).next_power_of_two(); + } +} + +#[test] +fn align_offset_stride1() { + // For pointers of stride = 1, the pointer can always be aligned. The offset is equal to + // number of bytes. + let mut align = 1; + while align < 1024 { + for ptr in 1..2*align { + let expected = ptr % align; + let offset = if expected == 0 { 0 } else { align - expected }; + assert_eq!((ptr as *const u8).align_offset(align), offset, + "ptr = {}, align = {}, size = 1", ptr, align); + } + align = (align + 1).next_power_of_two(); + } +} + +#[test] +fn align_offset_weird_strides() { + #[repr(packed)] + struct A3(u16, u8); + struct A4(u32); + #[repr(packed)] + struct A5(u32, u8); + #[repr(packed)] + struct A6(u32, u16); + #[repr(packed)] + struct A7(u32, u16, u8); + #[repr(packed)] + struct A8(u32, u32); + #[repr(packed)] + struct A9(u32, u32, u8); + #[repr(packed)] + struct A10(u32, u32, u16); + + unsafe fn test_weird_stride(ptr: *const T, align: usize) -> bool { + let numptr = ptr as usize; + let mut expected = usize::max_value(); + // Naive but definitely correct way to find the *first* aligned element of stride::. + for el in 0..align { + if (numptr + el * ::std::mem::size_of::()) % align == 0 { + expected = el; + break; + } + } + let got = ptr.align_offset(align); + if got != expected { + eprintln!("aligning {:p} (with stride of {}) to {}, expected {}, got {}", ptr, + ::std::mem::size_of::(), align, expected, got); + return true; + } + return false; + } + + // For pointers of stride != 1, we verify the algorithm against the naivest possible + // implementation + let mut align = 1; + let mut x = false; + while align < 1024 { + for ptr in 1usize..4*align { + unsafe { + x |= test_weird_stride::(ptr as *const A3, align); + x |= test_weird_stride::(ptr as *const A4, align); + x |= test_weird_stride::(ptr as *const A5, align); + x |= test_weird_stride::(ptr as *const A6, align); + x |= test_weird_stride::(ptr as *const A7, align); + x |= test_weird_stride::(ptr as *const A8, align); + x |= test_weird_stride::(ptr as *const A9, align); + x |= test_weird_stride::(ptr as *const A10, align); + } + } + align = (align + 1).next_power_of_two(); + } + assert!(!x); +} diff --git a/src/libcore/tests/slice.rs b/src/libcore/tests/slice.rs index 19b5c86c47406..fcd79222e1699 100644 --- a/src/libcore/tests/slice.rs +++ b/src/libcore/tests/slice.rs @@ -812,3 +812,37 @@ pub mod memchr { } } } + +#[test] +fn test_align_to_simple() { + let bytes = [1u8, 2, 3, 4, 5, 6, 7]; + let (prefix, aligned, suffix) = unsafe { bytes.align_to::() }; + assert_eq!(aligned.len(), 3); + assert!(prefix == [1] || suffix == [7]); + let expect1 = [1 << 8 | 2, 3 << 8 | 4, 5 << 8 | 6]; + let expect2 = [1 | 2 << 8, 3 | 4 << 8, 5 | 6 << 8]; + let expect3 = [2 << 8 | 3, 4 << 8 | 5, 6 << 8 | 7]; + let expect4 = [2 | 3 << 8, 4 | 5 << 8, 6 | 7 << 8]; + assert!(aligned == expect1 || aligned == expect2 || aligned == expect3 || aligned == expect4, + "aligned={:?} expected={:?} || {:?} || {:?} || {:?}", + aligned, expect1, expect2, expect3, expect4); +} + +#[test] +fn test_align_to_zst() { + let bytes = [1, 2, 3, 4, 5, 6, 7]; + let (prefix, aligned, suffix) = unsafe { bytes.align_to::<()>() }; + assert_eq!(aligned.len(), 0); + assert!(prefix == [1, 2, 3, 4, 5, 6, 7] || suffix == [1, 2, 3, 4, 5, 6, 7]); +} + +#[test] +fn test_align_to_non_trivial() { + #[repr(align(8))] struct U64(u64, u64); + #[repr(align(8))] struct U64U64U32(u64, u64, u32); + let data = [U64(1, 2), U64(3, 4), U64(5, 6), U64(7, 8), U64(9, 10), U64(11, 12), U64(13, 14), + U64(15, 16)]; + let (prefix, aligned, suffix) = unsafe { data.align_to::() }; + assert_eq!(aligned.len(), 4); + assert_eq!(prefix.len() + suffix.len(), 2); +} diff --git a/src/librustc/middle/lang_items.rs b/src/librustc/middle/lang_items.rs index 95e92e21b09dc..d70f994e87ba7 100644 --- a/src/librustc/middle/lang_items.rs +++ b/src/librustc/middle/lang_items.rs @@ -348,6 +348,9 @@ language_item_table! { I128ShroFnLangItem, "i128_shro", i128_shro_fn; U128ShroFnLangItem, "u128_shro", u128_shro_fn; + // Align offset for stride != 1, must not panic. + AlignOffsetLangItem, "align_offset", align_offset_fn; + TerminationTraitLangItem, "termination", termination; } diff --git a/src/librustc_codegen_llvm/intrinsic.rs b/src/librustc_codegen_llvm/intrinsic.rs index ba04cc7fad5e9..cffe7f79e970c 100644 --- a/src/librustc_codegen_llvm/intrinsic.rs +++ b/src/librustc_codegen_llvm/intrinsic.rs @@ -389,18 +389,6 @@ pub fn codegen_intrinsic_call<'a, 'tcx>(bx: &Builder<'a, 'tcx>, args[0].deref(bx.cx).codegen_get_discr(bx, ret_ty) } - "align_offset" => { - // `ptr as usize` - let ptr_val = bx.ptrtoint(args[0].immediate(), bx.cx.isize_ty); - // `ptr_val % align` - let align = args[1].immediate(); - let offset = bx.urem(ptr_val, align); - let zero = C_null(bx.cx.isize_ty); - // `offset == 0` - let is_zero = bx.icmp(llvm::IntPredicate::IntEQ, offset, zero); - // `if offset == 0 { 0 } else { align - offset }` - bx.select(is_zero, zero, bx.sub(align, offset)) - } name if name.starts_with("simd_") => { match generic_simd_intrinsic(bx, name, callee_ty, diff --git a/src/librustc_typeck/check/intrinsic.rs b/src/librustc_typeck/check/intrinsic.rs index feb26e7616257..af1f1044edf2f 100644 --- a/src/librustc_typeck/check/intrinsic.rs +++ b/src/librustc_typeck/check/intrinsic.rs @@ -314,11 +314,6 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, (0, vec![tcx.mk_fn_ptr(fn_ty), mut_u8, mut_u8], tcx.types.i32) } - "align_offset" => { - let ptr_ty = tcx.mk_imm_ptr(tcx.mk_nil()); - (0, vec![ptr_ty, tcx.types.usize], tcx.types.usize) - }, - "nontemporal_store" => { (1, vec![ tcx.mk_mut_ptr(param(0)), param(0) ], tcx.mk_nil()) } diff --git a/src/test/run-pass/align-offset-sign.rs b/src/test/run-pass/align-offset-sign.rs deleted file mode 100644 index aaa0419d061cb..0000000000000 --- a/src/test/run-pass/align-offset-sign.rs +++ /dev/null @@ -1,16 +0,0 @@ -// Copyright 2017 The Rust Project Developers. See the COPYRIGHT -// file at the top-level directory of this distribution and at -// http://rust-lang.org/COPYRIGHT. -// -// Licensed under the Apache License, Version 2.0 or the MIT license -// , at your -// option. This file may not be copied, modified, or distributed -// except according to those terms. - -#![feature(align_offset)] - -fn main() { - let x = 1 as *const u8; - assert_eq!(x.align_offset(8), 7); -}