1 pub use Integer::*; 2 pub use Primitive::*; 3 4 use crate::spec::Target; 5 6 use std::convert::{TryFrom, TryInto}; 7 use std::fmt; 8 use std::iter::Step; 9 use std::num::NonZeroUsize; 10 use std::ops::{Add, AddAssign, Deref, Mul, RangeInclusive, Sub}; 11 use std::str::FromStr; 12 13 use rustc_index::vec::{Idx, IndexVec}; 14 use rustc_macros::HashStable_Generic; 15 use rustc_serialize::json::{Json, ToJson}; 16 17 pub mod call; 18 19 /// Parsed [Data layout](https://llvm.org/docs/LangRef.html#data-layout) 20 /// for a target, which contains everything needed to compute layouts. 21 pub struct TargetDataLayout { 22 pub endian: Endian, 23 pub i1_align: AbiAndPrefAlign, 24 pub i8_align: AbiAndPrefAlign, 25 pub i16_align: AbiAndPrefAlign, 26 pub i32_align: AbiAndPrefAlign, 27 pub i64_align: AbiAndPrefAlign, 28 pub i128_align: AbiAndPrefAlign, 29 pub f32_align: AbiAndPrefAlign, 30 pub f64_align: AbiAndPrefAlign, 31 pub pointer_size: Size, 32 pub pointer_align: AbiAndPrefAlign, 33 pub aggregate_align: AbiAndPrefAlign, 34 35 /// Alignments for vector types. 36 pub vector_align: Vec<(Size, AbiAndPrefAlign)>, 37 38 pub instruction_address_space: AddressSpace, 39 40 /// Minimum size of #[repr(C)] enums (default I32 bits) 41 pub c_enum_min_size: Integer, 42 } 43 44 impl Default for TargetDataLayout { 45 /// Creates an instance of `TargetDataLayout`. default() -> TargetDataLayout46 fn default() -> TargetDataLayout { 47 let align = |bits| Align::from_bits(bits).unwrap(); 48 TargetDataLayout { 49 endian: Endian::Big, 50 i1_align: AbiAndPrefAlign::new(align(8)), 51 i8_align: AbiAndPrefAlign::new(align(8)), 52 i16_align: AbiAndPrefAlign::new(align(16)), 53 i32_align: AbiAndPrefAlign::new(align(32)), 54 i64_align: AbiAndPrefAlign { abi: align(32), pref: align(64) }, 55 i128_align: AbiAndPrefAlign { abi: align(32), pref: align(64) }, 56 f32_align: AbiAndPrefAlign::new(align(32)), 57 f64_align: AbiAndPrefAlign::new(align(64)), 58 pointer_size: Size::from_bits(64), 59 pointer_align: AbiAndPrefAlign::new(align(64)), 60 aggregate_align: AbiAndPrefAlign { abi: align(0), pref: align(64) }, 61 vector_align: vec![ 62 (Size::from_bits(64), AbiAndPrefAlign::new(align(64))), 63 (Size::from_bits(128), AbiAndPrefAlign::new(align(128))), 64 ], 65 instruction_address_space: AddressSpace::DATA, 66 c_enum_min_size: Integer::I32, 67 } 68 } 69 } 70 71 impl TargetDataLayout { parse(target: &Target) -> Result<TargetDataLayout, String>72 pub fn parse(target: &Target) -> Result<TargetDataLayout, String> { 73 // Parse an address space index from a string. 74 let parse_address_space = |s: &str, cause: &str| { 75 s.parse::<u32>().map(AddressSpace).map_err(|err| { 76 format!("invalid address space `{}` for `{}` in \"data-layout\": {}", s, cause, err) 77 }) 78 }; 79 80 // Parse a bit count from a string. 81 let parse_bits = |s: &str, kind: &str, cause: &str| { 82 s.parse::<u64>().map_err(|err| { 83 format!("invalid {} `{}` for `{}` in \"data-layout\": {}", kind, s, cause, err) 84 }) 85 }; 86 87 // Parse a size string. 88 let size = |s: &str, cause: &str| parse_bits(s, "size", cause).map(Size::from_bits); 89 90 // Parse an alignment string. 91 let align = |s: &[&str], cause: &str| { 92 if s.is_empty() { 93 return Err(format!("missing alignment for `{}` in \"data-layout\"", cause)); 94 } 95 let align_from_bits = |bits| { 96 Align::from_bits(bits).map_err(|err| { 97 format!("invalid alignment for `{}` in \"data-layout\": {}", cause, err) 98 }) 99 }; 100 let abi = parse_bits(s[0], "alignment", cause)?; 101 let pref = s.get(1).map_or(Ok(abi), |pref| parse_bits(pref, "alignment", cause))?; 102 Ok(AbiAndPrefAlign { abi: align_from_bits(abi)?, pref: align_from_bits(pref)? }) 103 }; 104 105 let mut dl = TargetDataLayout::default(); 106 let mut i128_align_src = 64; 107 for spec in target.data_layout.split('-') { 108 let spec_parts = spec.split(':').collect::<Vec<_>>(); 109 110 match &*spec_parts { 111 ["e"] => dl.endian = Endian::Little, 112 ["E"] => dl.endian = Endian::Big, 113 [p] if p.starts_with('P') => { 114 dl.instruction_address_space = parse_address_space(&p[1..], "P")? 115 } 116 ["a", ref a @ ..] => dl.aggregate_align = align(a, "a")?, 117 ["f32", ref a @ ..] => dl.f32_align = align(a, "f32")?, 118 ["f64", ref a @ ..] => dl.f64_align = align(a, "f64")?, 119 [p @ "p", s, ref a @ ..] | [p @ "p0", s, ref a @ ..] => { 120 dl.pointer_size = size(s, p)?; 121 dl.pointer_align = align(a, p)?; 122 } 123 [s, ref a @ ..] if s.starts_with('i') => { 124 let bits = match s[1..].parse::<u64>() { 125 Ok(bits) => bits, 126 Err(_) => { 127 size(&s[1..], "i")?; // For the user error. 128 continue; 129 } 130 }; 131 let a = align(a, s)?; 132 match bits { 133 1 => dl.i1_align = a, 134 8 => dl.i8_align = a, 135 16 => dl.i16_align = a, 136 32 => dl.i32_align = a, 137 64 => dl.i64_align = a, 138 _ => {} 139 } 140 if bits >= i128_align_src && bits <= 128 { 141 // Default alignment for i128 is decided by taking the alignment of 142 // largest-sized i{64..=128}. 143 i128_align_src = bits; 144 dl.i128_align = a; 145 } 146 } 147 [s, ref a @ ..] if s.starts_with('v') => { 148 let v_size = size(&s[1..], "v")?; 149 let a = align(a, s)?; 150 if let Some(v) = dl.vector_align.iter_mut().find(|v| v.0 == v_size) { 151 v.1 = a; 152 continue; 153 } 154 // No existing entry, add a new one. 155 dl.vector_align.push((v_size, a)); 156 } 157 _ => {} // Ignore everything else. 158 } 159 } 160 161 // Perform consistency checks against the Target information. 162 if dl.endian != target.endian { 163 return Err(format!( 164 "inconsistent target specification: \"data-layout\" claims \ 165 architecture is {}-endian, while \"target-endian\" is `{}`", 166 dl.endian.as_str(), 167 target.endian.as_str(), 168 )); 169 } 170 171 if dl.pointer_size.bits() != target.pointer_width.into() { 172 return Err(format!( 173 "inconsistent target specification: \"data-layout\" claims \ 174 pointers are {}-bit, while \"target-pointer-width\" is `{}`", 175 dl.pointer_size.bits(), 176 target.pointer_width 177 )); 178 } 179 180 dl.c_enum_min_size = Integer::from_size(Size::from_bits(target.c_enum_min_bits))?; 181 182 Ok(dl) 183 } 184 185 /// Returns exclusive upper bound on object size. 186 /// 187 /// The theoretical maximum object size is defined as the maximum positive `isize` value. 188 /// This ensures that the `offset` semantics remain well-defined by allowing it to correctly 189 /// index every address within an object along with one byte past the end, along with allowing 190 /// `isize` to store the difference between any two pointers into an object. 191 /// 192 /// The upper bound on 64-bit currently needs to be lower because LLVM uses a 64-bit integer 193 /// to represent object size in bits. It would need to be 1 << 61 to account for this, but is 194 /// currently conservatively bounded to 1 << 47 as that is enough to cover the current usable 195 /// address space on 64-bit ARMv8 and x86_64. 196 #[inline] obj_size_bound(&self) -> u64197 pub fn obj_size_bound(&self) -> u64 { 198 match self.pointer_size.bits() { 199 16 => 1 << 15, 200 32 => 1 << 31, 201 64 => 1 << 47, 202 bits => panic!("obj_size_bound: unknown pointer bit size {}", bits), 203 } 204 } 205 206 #[inline] ptr_sized_integer(&self) -> Integer207 pub fn ptr_sized_integer(&self) -> Integer { 208 match self.pointer_size.bits() { 209 16 => I16, 210 32 => I32, 211 64 => I64, 212 bits => panic!("ptr_sized_integer: unknown pointer bit size {}", bits), 213 } 214 } 215 216 #[inline] vector_align(&self, vec_size: Size) -> AbiAndPrefAlign217 pub fn vector_align(&self, vec_size: Size) -> AbiAndPrefAlign { 218 for &(size, align) in &self.vector_align { 219 if size == vec_size { 220 return align; 221 } 222 } 223 // Default to natural alignment, which is what LLVM does. 224 // That is, use the size, rounded up to a power of 2. 225 AbiAndPrefAlign::new(Align::from_bytes(vec_size.bytes().next_power_of_two()).unwrap()) 226 } 227 } 228 229 pub trait HasDataLayout { data_layout(&self) -> &TargetDataLayout230 fn data_layout(&self) -> &TargetDataLayout; 231 } 232 233 impl HasDataLayout for TargetDataLayout { 234 #[inline] data_layout(&self) -> &TargetDataLayout235 fn data_layout(&self) -> &TargetDataLayout { 236 self 237 } 238 } 239 240 /// Endianness of the target, which must match cfg(target-endian). 241 #[derive(Copy, Clone, PartialEq)] 242 pub enum Endian { 243 Little, 244 Big, 245 } 246 247 impl Endian { as_str(&self) -> &'static str248 pub fn as_str(&self) -> &'static str { 249 match self { 250 Self::Little => "little", 251 Self::Big => "big", 252 } 253 } 254 } 255 256 impl fmt::Debug for Endian { fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result257 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { 258 f.write_str(self.as_str()) 259 } 260 } 261 262 impl FromStr for Endian { 263 type Err = String; 264 from_str(s: &str) -> Result<Self, Self::Err>265 fn from_str(s: &str) -> Result<Self, Self::Err> { 266 match s { 267 "little" => Ok(Self::Little), 268 "big" => Ok(Self::Big), 269 _ => Err(format!(r#"unknown endian: "{}""#, s)), 270 } 271 } 272 } 273 274 impl ToJson for Endian { to_json(&self) -> Json275 fn to_json(&self) -> Json { 276 self.as_str().to_json() 277 } 278 } 279 280 /// Size of a type in bytes. 281 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)] 282 #[derive(HashStable_Generic)] 283 pub struct Size { 284 // The top 3 bits are ALWAYS zero. 285 raw: u64, 286 } 287 288 impl Size { 289 pub const ZERO: Size = Size { raw: 0 }; 290 291 /// Rounds `bits` up to the next-higher byte boundary, if `bits` is 292 /// is not aligned. from_bits(bits: impl TryInto<u64>) -> Size293 pub fn from_bits(bits: impl TryInto<u64>) -> Size { 294 let bits = bits.try_into().ok().unwrap(); 295 296 #[cold] 297 fn overflow(bits: u64) -> ! { 298 panic!("Size::from_bits({}) has overflowed", bits); 299 } 300 301 // This is the largest value of `bits` that does not cause overflow 302 // during rounding, and guarantees that the resulting number of bytes 303 // cannot cause overflow when multiplied by 8. 304 if bits > 0xffff_ffff_ffff_fff8 { 305 overflow(bits); 306 } 307 308 // Avoid potential overflow from `bits + 7`. 309 Size { raw: bits / 8 + ((bits % 8) + 7) / 8 } 310 } 311 312 #[inline] from_bytes(bytes: impl TryInto<u64>) -> Size313 pub fn from_bytes(bytes: impl TryInto<u64>) -> Size { 314 let bytes: u64 = bytes.try_into().ok().unwrap(); 315 Size { raw: bytes } 316 } 317 318 #[inline] bytes(self) -> u64319 pub fn bytes(self) -> u64 { 320 self.raw 321 } 322 323 #[inline] bytes_usize(self) -> usize324 pub fn bytes_usize(self) -> usize { 325 self.bytes().try_into().unwrap() 326 } 327 328 #[inline] bits(self) -> u64329 pub fn bits(self) -> u64 { 330 self.raw << 3 331 } 332 333 #[inline] bits_usize(self) -> usize334 pub fn bits_usize(self) -> usize { 335 self.bits().try_into().unwrap() 336 } 337 338 #[inline] align_to(self, align: Align) -> Size339 pub fn align_to(self, align: Align) -> Size { 340 let mask = align.bytes() - 1; 341 Size::from_bytes((self.bytes() + mask) & !mask) 342 } 343 344 #[inline] is_aligned(self, align: Align) -> bool345 pub fn is_aligned(self, align: Align) -> bool { 346 let mask = align.bytes() - 1; 347 self.bytes() & mask == 0 348 } 349 350 #[inline] checked_add<C: HasDataLayout>(self, offset: Size, cx: &C) -> Option<Size>351 pub fn checked_add<C: HasDataLayout>(self, offset: Size, cx: &C) -> Option<Size> { 352 let dl = cx.data_layout(); 353 354 let bytes = self.bytes().checked_add(offset.bytes())?; 355 356 if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None } 357 } 358 359 #[inline] checked_mul<C: HasDataLayout>(self, count: u64, cx: &C) -> Option<Size>360 pub fn checked_mul<C: HasDataLayout>(self, count: u64, cx: &C) -> Option<Size> { 361 let dl = cx.data_layout(); 362 363 let bytes = self.bytes().checked_mul(count)?; 364 if bytes < dl.obj_size_bound() { Some(Size::from_bytes(bytes)) } else { None } 365 } 366 367 /// Truncates `value` to `self` bits and then sign-extends it to 128 bits 368 /// (i.e., if it is negative, fill with 1's on the left). 369 #[inline] sign_extend(self, value: u128) -> u128370 pub fn sign_extend(self, value: u128) -> u128 { 371 let size = self.bits(); 372 if size == 0 { 373 // Truncated until nothing is left. 374 return 0; 375 } 376 // Sign-extend it. 377 let shift = 128 - size; 378 // Shift the unsigned value to the left, then shift back to the right as signed 379 // (essentially fills with sign bit on the left). 380 (((value << shift) as i128) >> shift) as u128 381 } 382 383 /// Truncates `value` to `self` bits. 384 #[inline] truncate(self, value: u128) -> u128385 pub fn truncate(self, value: u128) -> u128 { 386 let size = self.bits(); 387 if size == 0 { 388 // Truncated until nothing is left. 389 return 0; 390 } 391 let shift = 128 - size; 392 // Truncate (shift left to drop out leftover values, shift right to fill with zeroes). 393 (value << shift) >> shift 394 } 395 396 #[inline] signed_int_min(&self) -> i128397 pub fn signed_int_min(&self) -> i128 { 398 self.sign_extend(1_u128 << (self.bits() - 1)) as i128 399 } 400 401 #[inline] signed_int_max(&self) -> i128402 pub fn signed_int_max(&self) -> i128 { 403 i128::MAX >> (128 - self.bits()) 404 } 405 406 #[inline] unsigned_int_max(&self) -> u128407 pub fn unsigned_int_max(&self) -> u128 { 408 u128::MAX >> (128 - self.bits()) 409 } 410 } 411 412 // Panicking addition, subtraction and multiplication for convenience. 413 // Avoid during layout computation, return `LayoutError` instead. 414 415 impl Add for Size { 416 type Output = Size; 417 #[inline] add(self, other: Size) -> Size418 fn add(self, other: Size) -> Size { 419 Size::from_bytes(self.bytes().checked_add(other.bytes()).unwrap_or_else(|| { 420 panic!("Size::add: {} + {} doesn't fit in u64", self.bytes(), other.bytes()) 421 })) 422 } 423 } 424 425 impl Sub for Size { 426 type Output = Size; 427 #[inline] sub(self, other: Size) -> Size428 fn sub(self, other: Size) -> Size { 429 Size::from_bytes(self.bytes().checked_sub(other.bytes()).unwrap_or_else(|| { 430 panic!("Size::sub: {} - {} would result in negative size", self.bytes(), other.bytes()) 431 })) 432 } 433 } 434 435 impl Mul<Size> for u64 { 436 type Output = Size; 437 #[inline] mul(self, size: Size) -> Size438 fn mul(self, size: Size) -> Size { 439 size * self 440 } 441 } 442 443 impl Mul<u64> for Size { 444 type Output = Size; 445 #[inline] mul(self, count: u64) -> Size446 fn mul(self, count: u64) -> Size { 447 match self.bytes().checked_mul(count) { 448 Some(bytes) => Size::from_bytes(bytes), 449 None => panic!("Size::mul: {} * {} doesn't fit in u64", self.bytes(), count), 450 } 451 } 452 } 453 454 impl AddAssign for Size { 455 #[inline] add_assign(&mut self, other: Size)456 fn add_assign(&mut self, other: Size) { 457 *self = *self + other; 458 } 459 } 460 461 impl Step for Size { 462 #[inline] steps_between(start: &Self, end: &Self) -> Option<usize>463 fn steps_between(start: &Self, end: &Self) -> Option<usize> { 464 u64::steps_between(&start.bytes(), &end.bytes()) 465 } 466 467 #[inline] forward_checked(start: Self, count: usize) -> Option<Self>468 fn forward_checked(start: Self, count: usize) -> Option<Self> { 469 u64::forward_checked(start.bytes(), count).map(Self::from_bytes) 470 } 471 472 #[inline] forward(start: Self, count: usize) -> Self473 fn forward(start: Self, count: usize) -> Self { 474 Self::from_bytes(u64::forward(start.bytes(), count)) 475 } 476 477 #[inline] forward_unchecked(start: Self, count: usize) -> Self478 unsafe fn forward_unchecked(start: Self, count: usize) -> Self { 479 Self::from_bytes(u64::forward_unchecked(start.bytes(), count)) 480 } 481 482 #[inline] backward_checked(start: Self, count: usize) -> Option<Self>483 fn backward_checked(start: Self, count: usize) -> Option<Self> { 484 u64::backward_checked(start.bytes(), count).map(Self::from_bytes) 485 } 486 487 #[inline] backward(start: Self, count: usize) -> Self488 fn backward(start: Self, count: usize) -> Self { 489 Self::from_bytes(u64::backward(start.bytes(), count)) 490 } 491 492 #[inline] backward_unchecked(start: Self, count: usize) -> Self493 unsafe fn backward_unchecked(start: Self, count: usize) -> Self { 494 Self::from_bytes(u64::backward_unchecked(start.bytes(), count)) 495 } 496 } 497 498 /// Alignment of a type in bytes (always a power of two). 499 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, Encodable, Decodable)] 500 #[derive(HashStable_Generic)] 501 pub struct Align { 502 pow2: u8, 503 } 504 505 impl Align { 506 pub const ONE: Align = Align { pow2: 0 }; 507 508 #[inline] from_bits(bits: u64) -> Result<Align, String>509 pub fn from_bits(bits: u64) -> Result<Align, String> { 510 Align::from_bytes(Size::from_bits(bits).bytes()) 511 } 512 513 #[inline] from_bytes(align: u64) -> Result<Align, String>514 pub fn from_bytes(align: u64) -> Result<Align, String> { 515 // Treat an alignment of 0 bytes like 1-byte alignment. 516 if align == 0 { 517 return Ok(Align::ONE); 518 } 519 520 #[cold] 521 fn not_power_of_2(align: u64) -> String { 522 format!("`{}` is not a power of 2", align) 523 } 524 525 #[cold] 526 fn too_large(align: u64) -> String { 527 format!("`{}` is too large", align) 528 } 529 530 let mut bytes = align; 531 let mut pow2: u8 = 0; 532 while (bytes & 1) == 0 { 533 pow2 += 1; 534 bytes >>= 1; 535 } 536 if bytes != 1 { 537 return Err(not_power_of_2(align)); 538 } 539 if pow2 > 29 { 540 return Err(too_large(align)); 541 } 542 543 Ok(Align { pow2 }) 544 } 545 546 #[inline] bytes(self) -> u64547 pub fn bytes(self) -> u64 { 548 1 << self.pow2 549 } 550 551 #[inline] bits(self) -> u64552 pub fn bits(self) -> u64 { 553 self.bytes() * 8 554 } 555 556 /// Computes the best alignment possible for the given offset 557 /// (the largest power of two that the offset is a multiple of). 558 /// 559 /// N.B., for an offset of `0`, this happens to return `2^64`. 560 #[inline] max_for_offset(offset: Size) -> Align561 pub fn max_for_offset(offset: Size) -> Align { 562 Align { pow2: offset.bytes().trailing_zeros() as u8 } 563 } 564 565 /// Lower the alignment, if necessary, such that the given offset 566 /// is aligned to it (the offset is a multiple of the alignment). 567 #[inline] restrict_for_offset(self, offset: Size) -> Align568 pub fn restrict_for_offset(self, offset: Size) -> Align { 569 self.min(Align::max_for_offset(offset)) 570 } 571 } 572 573 /// A pair of alignments, ABI-mandated and preferred. 574 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, Encodable, Decodable)] 575 #[derive(HashStable_Generic)] 576 pub struct AbiAndPrefAlign { 577 pub abi: Align, 578 pub pref: Align, 579 } 580 581 impl AbiAndPrefAlign { 582 #[inline] new(align: Align) -> AbiAndPrefAlign583 pub fn new(align: Align) -> AbiAndPrefAlign { 584 AbiAndPrefAlign { abi: align, pref: align } 585 } 586 587 #[inline] min(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign588 pub fn min(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign { 589 AbiAndPrefAlign { abi: self.abi.min(other.abi), pref: self.pref.min(other.pref) } 590 } 591 592 #[inline] max(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign593 pub fn max(self, other: AbiAndPrefAlign) -> AbiAndPrefAlign { 594 AbiAndPrefAlign { abi: self.abi.max(other.abi), pref: self.pref.max(other.pref) } 595 } 596 } 597 598 /// Integers, also used for enum discriminants. 599 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, HashStable_Generic)] 600 pub enum Integer { 601 I8, 602 I16, 603 I32, 604 I64, 605 I128, 606 } 607 608 impl Integer { 609 #[inline] size(self) -> Size610 pub fn size(self) -> Size { 611 match self { 612 I8 => Size::from_bytes(1), 613 I16 => Size::from_bytes(2), 614 I32 => Size::from_bytes(4), 615 I64 => Size::from_bytes(8), 616 I128 => Size::from_bytes(16), 617 } 618 } 619 align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign620 pub fn align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign { 621 let dl = cx.data_layout(); 622 623 match self { 624 I8 => dl.i8_align, 625 I16 => dl.i16_align, 626 I32 => dl.i32_align, 627 I64 => dl.i64_align, 628 I128 => dl.i128_align, 629 } 630 } 631 632 /// Finds the smallest Integer type which can represent the signed value. 633 #[inline] fit_signed(x: i128) -> Integer634 pub fn fit_signed(x: i128) -> Integer { 635 match x { 636 -0x0000_0000_0000_0080..=0x0000_0000_0000_007f => I8, 637 -0x0000_0000_0000_8000..=0x0000_0000_0000_7fff => I16, 638 -0x0000_0000_8000_0000..=0x0000_0000_7fff_ffff => I32, 639 -0x8000_0000_0000_0000..=0x7fff_ffff_ffff_ffff => I64, 640 _ => I128, 641 } 642 } 643 644 /// Finds the smallest Integer type which can represent the unsigned value. 645 #[inline] fit_unsigned(x: u128) -> Integer646 pub fn fit_unsigned(x: u128) -> Integer { 647 match x { 648 0..=0x0000_0000_0000_00ff => I8, 649 0..=0x0000_0000_0000_ffff => I16, 650 0..=0x0000_0000_ffff_ffff => I32, 651 0..=0xffff_ffff_ffff_ffff => I64, 652 _ => I128, 653 } 654 } 655 656 /// Finds the smallest integer with the given alignment. for_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Option<Integer>657 pub fn for_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Option<Integer> { 658 let dl = cx.data_layout(); 659 660 for candidate in [I8, I16, I32, I64, I128] { 661 if wanted == candidate.align(dl).abi && wanted.bytes() == candidate.size().bytes() { 662 return Some(candidate); 663 } 664 } 665 None 666 } 667 668 /// Find the largest integer with the given alignment or less. approximate_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Integer669 pub fn approximate_align<C: HasDataLayout>(cx: &C, wanted: Align) -> Integer { 670 let dl = cx.data_layout(); 671 672 // FIXME(eddyb) maybe include I128 in the future, when it works everywhere. 673 for candidate in [I64, I32, I16] { 674 if wanted >= candidate.align(dl).abi && wanted.bytes() >= candidate.size().bytes() { 675 return candidate; 676 } 677 } 678 I8 679 } 680 681 // FIXME(eddyb) consolidate this and other methods that find the appropriate 682 // `Integer` given some requirements. 683 #[inline] from_size(size: Size) -> Result<Self, String>684 fn from_size(size: Size) -> Result<Self, String> { 685 match size.bits() { 686 8 => Ok(Integer::I8), 687 16 => Ok(Integer::I16), 688 32 => Ok(Integer::I32), 689 64 => Ok(Integer::I64), 690 128 => Ok(Integer::I128), 691 _ => Err(format!("rust does not support integers with {} bits", size.bits())), 692 } 693 } 694 } 695 696 /// Fundamental unit of memory access and layout. 697 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, HashStable_Generic)] 698 pub enum Primitive { 699 /// The `bool` is the signedness of the `Integer` type. 700 /// 701 /// One would think we would not care about such details this low down, 702 /// but some ABIs are described in terms of C types and ISAs where the 703 /// integer arithmetic is done on {sign,zero}-extended registers, e.g. 704 /// a negative integer passed by zero-extension will appear positive in 705 /// the callee, and most operations on it will produce the wrong values. 706 Int(Integer, bool), 707 F32, 708 F64, 709 Pointer, 710 } 711 712 impl Primitive { size<C: HasDataLayout>(self, cx: &C) -> Size713 pub fn size<C: HasDataLayout>(self, cx: &C) -> Size { 714 let dl = cx.data_layout(); 715 716 match self { 717 Int(i, _) => i.size(), 718 F32 => Size::from_bits(32), 719 F64 => Size::from_bits(64), 720 Pointer => dl.pointer_size, 721 } 722 } 723 align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign724 pub fn align<C: HasDataLayout>(self, cx: &C) -> AbiAndPrefAlign { 725 let dl = cx.data_layout(); 726 727 match self { 728 Int(i, _) => i.align(dl), 729 F32 => dl.f32_align, 730 F64 => dl.f64_align, 731 Pointer => dl.pointer_align, 732 } 733 } 734 735 // FIXME(eddyb) remove, it's trivial thanks to `matches!`. 736 #[inline] is_float(self) -> bool737 pub fn is_float(self) -> bool { 738 matches!(self, F32 | F64) 739 } 740 741 // FIXME(eddyb) remove, it's completely unused. 742 #[inline] is_int(self) -> bool743 pub fn is_int(self) -> bool { 744 matches!(self, Int(..)) 745 } 746 } 747 748 /// Inclusive wrap-around range of valid values, that is, if 749 /// start > end, it represents `start..=MAX`, 750 /// followed by `0..=end`. 751 /// 752 /// That is, for an i8 primitive, a range of `254..=2` means following 753 /// sequence: 754 /// 755 /// 254 (-2), 255 (-1), 0, 1, 2 756 /// 757 /// This is intended specifically to mirror LLVM’s `!range` metadata semantics. 758 #[derive(Clone, Copy, PartialEq, Eq, Hash)] 759 #[derive(HashStable_Generic)] 760 pub struct WrappingRange { 761 pub start: u128, 762 pub end: u128, 763 } 764 765 impl WrappingRange { 766 /// Returns `true` if `v` is contained in the range. 767 #[inline(always)] contains(&self, v: u128) -> bool768 pub fn contains(&self, v: u128) -> bool { 769 if self.start <= self.end { 770 self.start <= v && v <= self.end 771 } else { 772 self.start <= v || v <= self.end 773 } 774 } 775 776 /// Returns `self` with replaced `start` 777 #[inline(always)] with_start(mut self, start: u128) -> Self778 pub fn with_start(mut self, start: u128) -> Self { 779 self.start = start; 780 self 781 } 782 783 /// Returns `self` with replaced `end` 784 #[inline(always)] with_end(mut self, end: u128) -> Self785 pub fn with_end(mut self, end: u128) -> Self { 786 self.end = end; 787 self 788 } 789 790 /// Returns `true` if `size` completely fills the range. 791 #[inline] is_full_for(&self, size: Size) -> bool792 pub fn is_full_for(&self, size: Size) -> bool { 793 let max_value = size.unsigned_int_max(); 794 debug_assert!(self.start <= max_value && self.end <= max_value); 795 self.start == (self.end.wrapping_add(1) & max_value) 796 } 797 } 798 799 impl fmt::Debug for WrappingRange { fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result800 fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result { 801 if self.start > self.end { 802 write!(fmt, "(..={}) | ({}..)", self.end, self.start)?; 803 } else { 804 write!(fmt, "{}..={}", self.start, self.end)?; 805 } 806 Ok(()) 807 } 808 } 809 810 /// Information about one scalar component of a Rust type. 811 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)] 812 #[derive(HashStable_Generic)] 813 pub struct Scalar { 814 pub value: Primitive, 815 816 // FIXME(eddyb) always use the shortest range, e.g., by finding 817 // the largest space between two consecutive valid values and 818 // taking everything else as the (shortest) valid range. 819 pub valid_range: WrappingRange, 820 } 821 822 impl Scalar { 823 #[inline] is_bool(&self) -> bool824 pub fn is_bool(&self) -> bool { 825 matches!( 826 self, 827 Scalar { value: Int(I8, false), valid_range: WrappingRange { start: 0, end: 1 } } 828 ) 829 } 830 831 /// Returns `true` if all possible numbers are valid, i.e `valid_range` covers the whole layout 832 #[inline] is_always_valid<C: HasDataLayout>(&self, cx: &C) -> bool833 pub fn is_always_valid<C: HasDataLayout>(&self, cx: &C) -> bool { 834 self.valid_range.is_full_for(self.value.size(cx)) 835 } 836 } 837 838 /// Describes how the fields of a type are located in memory. 839 #[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)] 840 pub enum FieldsShape { 841 /// Scalar primitives and `!`, which never have fields. 842 Primitive, 843 844 /// All fields start at no offset. The `usize` is the field count. 845 Union(NonZeroUsize), 846 847 /// Array/vector-like placement, with all fields of identical types. 848 Array { stride: Size, count: u64 }, 849 850 /// Struct-like placement, with precomputed offsets. 851 /// 852 /// Fields are guaranteed to not overlap, but note that gaps 853 /// before, between and after all the fields are NOT always 854 /// padding, and as such their contents may not be discarded. 855 /// For example, enum variants leave a gap at the start, 856 /// where the discriminant field in the enum layout goes. 857 Arbitrary { 858 /// Offsets for the first byte of each field, 859 /// ordered to match the source definition order. 860 /// This vector does not go in increasing order. 861 // FIXME(eddyb) use small vector optimization for the common case. 862 offsets: Vec<Size>, 863 864 /// Maps source order field indices to memory order indices, 865 /// depending on how the fields were reordered (if at all). 866 /// This is a permutation, with both the source order and the 867 /// memory order using the same (0..n) index ranges. 868 /// 869 /// Note that during computation of `memory_index`, sometimes 870 /// it is easier to operate on the inverse mapping (that is, 871 /// from memory order to source order), and that is usually 872 /// named `inverse_memory_index`. 873 /// 874 // FIXME(eddyb) build a better abstraction for permutations, if possible. 875 // FIXME(camlorn) also consider small vector optimization here. 876 memory_index: Vec<u32>, 877 }, 878 } 879 880 impl FieldsShape { 881 #[inline] count(&self) -> usize882 pub fn count(&self) -> usize { 883 match *self { 884 FieldsShape::Primitive => 0, 885 FieldsShape::Union(count) => count.get(), 886 FieldsShape::Array { count, .. } => count.try_into().unwrap(), 887 FieldsShape::Arbitrary { ref offsets, .. } => offsets.len(), 888 } 889 } 890 891 #[inline] offset(&self, i: usize) -> Size892 pub fn offset(&self, i: usize) -> Size { 893 match *self { 894 FieldsShape::Primitive => { 895 unreachable!("FieldsShape::offset: `Primitive`s have no fields") 896 } 897 FieldsShape::Union(count) => { 898 assert!( 899 i < count.get(), 900 "tried to access field {} of union with {} fields", 901 i, 902 count 903 ); 904 Size::ZERO 905 } 906 FieldsShape::Array { stride, count } => { 907 let i = u64::try_from(i).unwrap(); 908 assert!(i < count); 909 stride * i 910 } 911 FieldsShape::Arbitrary { ref offsets, .. } => offsets[i], 912 } 913 } 914 915 #[inline] memory_index(&self, i: usize) -> usize916 pub fn memory_index(&self, i: usize) -> usize { 917 match *self { 918 FieldsShape::Primitive => { 919 unreachable!("FieldsShape::memory_index: `Primitive`s have no fields") 920 } 921 FieldsShape::Union(_) | FieldsShape::Array { .. } => i, 922 FieldsShape::Arbitrary { ref memory_index, .. } => memory_index[i].try_into().unwrap(), 923 } 924 } 925 926 /// Gets source indices of the fields by increasing offsets. 927 #[inline] index_by_increasing_offset<'a>(&'a self) -> impl Iterator<Item = usize> + 'a928 pub fn index_by_increasing_offset<'a>(&'a self) -> impl Iterator<Item = usize> + 'a { 929 let mut inverse_small = [0u8; 64]; 930 let mut inverse_big = vec![]; 931 let use_small = self.count() <= inverse_small.len(); 932 933 // We have to write this logic twice in order to keep the array small. 934 if let FieldsShape::Arbitrary { ref memory_index, .. } = *self { 935 if use_small { 936 for i in 0..self.count() { 937 inverse_small[memory_index[i] as usize] = i as u8; 938 } 939 } else { 940 inverse_big = vec![0; self.count()]; 941 for i in 0..self.count() { 942 inverse_big[memory_index[i] as usize] = i as u32; 943 } 944 } 945 } 946 947 (0..self.count()).map(move |i| match *self { 948 FieldsShape::Primitive | FieldsShape::Union(_) | FieldsShape::Array { .. } => i, 949 FieldsShape::Arbitrary { .. } => { 950 if use_small { 951 inverse_small[i] as usize 952 } else { 953 inverse_big[i] as usize 954 } 955 } 956 }) 957 } 958 } 959 960 /// An identifier that specifies the address space that some operation 961 /// should operate on. Special address spaces have an effect on code generation, 962 /// depending on the target and the address spaces it implements. 963 #[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord)] 964 pub struct AddressSpace(pub u32); 965 966 impl AddressSpace { 967 /// The default address space, corresponding to data space. 968 pub const DATA: Self = AddressSpace(0); 969 } 970 971 /// Describes how values of the type are passed by target ABIs, 972 /// in terms of categories of C types there are ABI rules for. 973 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable_Generic)] 974 pub enum Abi { 975 Uninhabited, 976 Scalar(Scalar), 977 ScalarPair(Scalar, Scalar), 978 Vector { 979 element: Scalar, 980 count: u64, 981 }, 982 Aggregate { 983 /// If true, the size is exact, otherwise it's only a lower bound. 984 sized: bool, 985 }, 986 } 987 988 impl Abi { 989 /// Returns `true` if the layout corresponds to an unsized type. 990 #[inline] is_unsized(&self) -> bool991 pub fn is_unsized(&self) -> bool { 992 match *self { 993 Abi::Uninhabited | Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false, 994 Abi::Aggregate { sized } => !sized, 995 } 996 } 997 998 /// Returns `true` if this is a single signed integer scalar 999 #[inline] is_signed(&self) -> bool1000 pub fn is_signed(&self) -> bool { 1001 match self { 1002 Abi::Scalar(scal) => match scal.value { 1003 Primitive::Int(_, signed) => signed, 1004 _ => false, 1005 }, 1006 _ => panic!("`is_signed` on non-scalar ABI {:?}", self), 1007 } 1008 } 1009 1010 /// Returns `true` if this is an uninhabited type 1011 #[inline] is_uninhabited(&self) -> bool1012 pub fn is_uninhabited(&self) -> bool { 1013 matches!(*self, Abi::Uninhabited) 1014 } 1015 1016 /// Returns `true` is this is a scalar type 1017 #[inline] is_scalar(&self) -> bool1018 pub fn is_scalar(&self) -> bool { 1019 matches!(*self, Abi::Scalar(_)) 1020 } 1021 } 1022 1023 rustc_index::newtype_index! { 1024 pub struct VariantIdx { 1025 derive [HashStable_Generic] 1026 } 1027 } 1028 1029 #[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)] 1030 pub enum Variants { 1031 /// Single enum variants, structs/tuples, unions, and all non-ADTs. 1032 Single { index: VariantIdx }, 1033 1034 /// Enum-likes with more than one inhabited variant: each variant comes with 1035 /// a *discriminant* (usually the same as the variant index but the user can 1036 /// assign explicit discriminant values). That discriminant is encoded 1037 /// as a *tag* on the machine. The layout of each variant is 1038 /// a struct, and they all have space reserved for the tag. 1039 /// For enums, the tag is the sole field of the layout. 1040 Multiple { 1041 tag: Scalar, 1042 tag_encoding: TagEncoding, 1043 tag_field: usize, 1044 variants: IndexVec<VariantIdx, Layout>, 1045 }, 1046 } 1047 1048 #[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)] 1049 pub enum TagEncoding { 1050 /// The tag directly stores the discriminant, but possibly with a smaller layout 1051 /// (so converting the tag to the discriminant can require sign extension). 1052 Direct, 1053 1054 /// Niche (values invalid for a type) encoding the discriminant: 1055 /// Discriminant and variant index coincide. 1056 /// The variant `dataful_variant` contains a niche at an arbitrary 1057 /// offset (field `tag_field` of the enum), which for a variant with 1058 /// discriminant `d` is set to 1059 /// `(d - niche_variants.start).wrapping_add(niche_start)`. 1060 /// 1061 /// For example, `Option<(usize, &T)>` is represented such that 1062 /// `None` has a null pointer for the second tuple field, and 1063 /// `Some` is the identity function (with a non-null reference). 1064 Niche { 1065 dataful_variant: VariantIdx, 1066 niche_variants: RangeInclusive<VariantIdx>, 1067 niche_start: u128, 1068 }, 1069 } 1070 1071 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, HashStable_Generic)] 1072 pub struct Niche { 1073 pub offset: Size, 1074 pub scalar: Scalar, 1075 } 1076 1077 impl Niche { from_scalar<C: HasDataLayout>(cx: &C, offset: Size, scalar: Scalar) -> Option<Self>1078 pub fn from_scalar<C: HasDataLayout>(cx: &C, offset: Size, scalar: Scalar) -> Option<Self> { 1079 let niche = Niche { offset, scalar }; 1080 if niche.available(cx) > 0 { Some(niche) } else { None } 1081 } 1082 available<C: HasDataLayout>(&self, cx: &C) -> u1281083 pub fn available<C: HasDataLayout>(&self, cx: &C) -> u128 { 1084 let Scalar { value, valid_range: v } = self.scalar; 1085 let size = value.size(cx); 1086 assert!(size.bits() <= 128); 1087 let max_value = size.unsigned_int_max(); 1088 1089 // Find out how many values are outside the valid range. 1090 let niche = v.end.wrapping_add(1)..v.start; 1091 niche.end.wrapping_sub(niche.start) & max_value 1092 } 1093 reserve<C: HasDataLayout>(&self, cx: &C, count: u128) -> Option<(u128, Scalar)>1094 pub fn reserve<C: HasDataLayout>(&self, cx: &C, count: u128) -> Option<(u128, Scalar)> { 1095 assert!(count > 0); 1096 1097 let Scalar { value, valid_range: v } = self.scalar; 1098 let size = value.size(cx); 1099 assert!(size.bits() <= 128); 1100 let max_value = size.unsigned_int_max(); 1101 1102 let niche = v.end.wrapping_add(1)..v.start; 1103 let available = niche.end.wrapping_sub(niche.start) & max_value; 1104 if count > available { 1105 return None; 1106 } 1107 1108 // Extend the range of valid values being reserved by moving either `v.start` or `v.end` bound. 1109 // Given an eventual `Option<T>`, we try to maximize the chance for `None` to occupy the niche of zero. 1110 // This is accomplished by prefering enums with 2 variants(`count==1`) and always taking the shortest path to niche zero. 1111 // Having `None` in niche zero can enable some special optimizations. 1112 // 1113 // Bound selection criteria: 1114 // 1. Select closest to zero given wrapping semantics. 1115 // 2. Avoid moving past zero if possible. 1116 // 1117 // In practice this means that enums with `count > 1` are unlikely to claim niche zero, since they have to fit perfectly. 1118 // If niche zero is already reserved, the selection of bounds are of little interest. 1119 let move_start = |v: WrappingRange| { 1120 let start = v.start.wrapping_sub(count) & max_value; 1121 Some((start, Scalar { value, valid_range: v.with_start(start) })) 1122 }; 1123 let move_end = |v: WrappingRange| { 1124 let start = v.end.wrapping_add(1) & max_value; 1125 let end = v.end.wrapping_add(count) & max_value; 1126 Some((start, Scalar { value, valid_range: v.with_end(end) })) 1127 }; 1128 let distance_end_zero = max_value - v.end; 1129 if v.start > v.end { 1130 // zero is unavailable because wrapping occurs 1131 move_end(v) 1132 } else if v.start <= distance_end_zero { 1133 if count <= v.start { 1134 move_start(v) 1135 } else { 1136 // moved past zero, use other bound 1137 move_end(v) 1138 } 1139 } else { 1140 let end = v.end.wrapping_add(count) & max_value; 1141 let overshot_zero = (1..=v.end).contains(&end); 1142 if overshot_zero { 1143 // moved past zero, use other bound 1144 move_start(v) 1145 } else { 1146 move_end(v) 1147 } 1148 } 1149 } 1150 } 1151 1152 #[derive(PartialEq, Eq, Hash, Debug, HashStable_Generic)] 1153 pub struct Layout { 1154 /// Says where the fields are located within the layout. 1155 pub fields: FieldsShape, 1156 1157 /// Encodes information about multi-variant layouts. 1158 /// Even with `Multiple` variants, a layout still has its own fields! Those are then 1159 /// shared between all variants. One of them will be the discriminant, 1160 /// but e.g. generators can have more. 1161 /// 1162 /// To access all fields of this layout, both `fields` and the fields of the active variant 1163 /// must be taken into account. 1164 pub variants: Variants, 1165 1166 /// The `abi` defines how this data is passed between functions, and it defines 1167 /// value restrictions via `valid_range`. 1168 /// 1169 /// Note that this is entirely orthogonal to the recursive structure defined by 1170 /// `variants` and `fields`; for example, `ManuallyDrop<Result<isize, isize>>` has 1171 /// `Abi::ScalarPair`! So, even with non-`Aggregate` `abi`, `fields` and `variants` 1172 /// have to be taken into account to find all fields of this layout. 1173 pub abi: Abi, 1174 1175 /// The leaf scalar with the largest number of invalid values 1176 /// (i.e. outside of its `valid_range`), if it exists. 1177 pub largest_niche: Option<Niche>, 1178 1179 pub align: AbiAndPrefAlign, 1180 pub size: Size, 1181 } 1182 1183 impl Layout { scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self1184 pub fn scalar<C: HasDataLayout>(cx: &C, scalar: Scalar) -> Self { 1185 let largest_niche = Niche::from_scalar(cx, Size::ZERO, scalar); 1186 let size = scalar.value.size(cx); 1187 let align = scalar.value.align(cx); 1188 Layout { 1189 variants: Variants::Single { index: VariantIdx::new(0) }, 1190 fields: FieldsShape::Primitive, 1191 abi: Abi::Scalar(scalar), 1192 largest_niche, 1193 size, 1194 align, 1195 } 1196 } 1197 } 1198 1199 /// The layout of a type, alongside the type itself. 1200 /// Provides various type traversal APIs (e.g., recursing into fields). 1201 /// 1202 /// Note that the layout is NOT guaranteed to always be identical 1203 /// to that obtained from `layout_of(ty)`, as we need to produce 1204 /// layouts for which Rust types do not exist, such as enum variants 1205 /// or synthetic fields of enums (i.e., discriminants) and fat pointers. 1206 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable_Generic)] 1207 pub struct TyAndLayout<'a, Ty> { 1208 pub ty: Ty, 1209 pub layout: &'a Layout, 1210 } 1211 1212 impl<'a, Ty> Deref for TyAndLayout<'a, Ty> { 1213 type Target = &'a Layout; deref(&self) -> &&'a Layout1214 fn deref(&self) -> &&'a Layout { 1215 &self.layout 1216 } 1217 } 1218 1219 #[derive(Copy, Clone, PartialEq, Eq, Debug)] 1220 pub enum PointerKind { 1221 /// Most general case, we know no restrictions to tell LLVM. 1222 Shared, 1223 1224 /// `&T` where `T` contains no `UnsafeCell`, is `noalias` and `readonly`. 1225 Frozen, 1226 1227 /// `&mut T` which is `noalias` but not `readonly`. 1228 UniqueBorrowed, 1229 1230 /// `Box<T>`, unlike `UniqueBorrowed`, it also has `noalias` on returns. 1231 UniqueOwned, 1232 } 1233 1234 #[derive(Copy, Clone, Debug)] 1235 pub struct PointeeInfo { 1236 pub size: Size, 1237 pub align: Align, 1238 pub safe: Option<PointerKind>, 1239 pub address_space: AddressSpace, 1240 } 1241 1242 /// Trait that needs to be implemented by the higher-level type representation 1243 /// (e.g. `rustc_middle::ty::Ty`), to provide `rustc_target::abi` functionality. 1244 pub trait TyAbiInterface<'a, C>: Sized { ty_and_layout_for_variant( this: TyAndLayout<'a, Self>, cx: &C, variant_index: VariantIdx, ) -> TyAndLayout<'a, Self>1245 fn ty_and_layout_for_variant( 1246 this: TyAndLayout<'a, Self>, 1247 cx: &C, 1248 variant_index: VariantIdx, 1249 ) -> TyAndLayout<'a, Self>; ty_and_layout_field(this: TyAndLayout<'a, Self>, cx: &C, i: usize) -> TyAndLayout<'a, Self>1250 fn ty_and_layout_field(this: TyAndLayout<'a, Self>, cx: &C, i: usize) -> TyAndLayout<'a, Self>; ty_and_layout_pointee_info_at( this: TyAndLayout<'a, Self>, cx: &C, offset: Size, ) -> Option<PointeeInfo>1251 fn ty_and_layout_pointee_info_at( 1252 this: TyAndLayout<'a, Self>, 1253 cx: &C, 1254 offset: Size, 1255 ) -> Option<PointeeInfo>; 1256 } 1257 1258 impl<'a, Ty> TyAndLayout<'a, Ty> { for_variant<C>(self, cx: &C, variant_index: VariantIdx) -> Self where Ty: TyAbiInterface<'a, C>,1259 pub fn for_variant<C>(self, cx: &C, variant_index: VariantIdx) -> Self 1260 where 1261 Ty: TyAbiInterface<'a, C>, 1262 { 1263 Ty::ty_and_layout_for_variant(self, cx, variant_index) 1264 } 1265 field<C>(self, cx: &C, i: usize) -> Self where Ty: TyAbiInterface<'a, C>,1266 pub fn field<C>(self, cx: &C, i: usize) -> Self 1267 where 1268 Ty: TyAbiInterface<'a, C>, 1269 { 1270 Ty::ty_and_layout_field(self, cx, i) 1271 } 1272 pointee_info_at<C>(self, cx: &C, offset: Size) -> Option<PointeeInfo> where Ty: TyAbiInterface<'a, C>,1273 pub fn pointee_info_at<C>(self, cx: &C, offset: Size) -> Option<PointeeInfo> 1274 where 1275 Ty: TyAbiInterface<'a, C>, 1276 { 1277 Ty::ty_and_layout_pointee_info_at(self, cx, offset) 1278 } 1279 } 1280 1281 impl<'a, Ty> TyAndLayout<'a, Ty> { 1282 /// Returns `true` if the layout corresponds to an unsized type. is_unsized(&self) -> bool1283 pub fn is_unsized(&self) -> bool { 1284 self.abi.is_unsized() 1285 } 1286 1287 /// Returns `true` if the type is a ZST and not unsized. is_zst(&self) -> bool1288 pub fn is_zst(&self) -> bool { 1289 match self.abi { 1290 Abi::Scalar(_) | Abi::ScalarPair(..) | Abi::Vector { .. } => false, 1291 Abi::Uninhabited => self.size.bytes() == 0, 1292 Abi::Aggregate { sized } => sized && self.size.bytes() == 0, 1293 } 1294 } 1295 1296 /// Determines if this type permits "raw" initialization by just transmuting some 1297 /// memory into an instance of `T`. 1298 /// `zero` indicates if the memory is zero-initialized, or alternatively 1299 /// left entirely uninitialized. 1300 /// This is conservative: in doubt, it will answer `true`. 1301 /// 1302 /// FIXME: Once we removed all the conservatism, we could alternatively 1303 /// create an all-0/all-undef constant and run the const value validator to see if 1304 /// this is a valid value for the given type. might_permit_raw_init<C>(self, cx: &C, zero: bool) -> bool where Self: Copy, Ty: TyAbiInterface<'a, C>, C: HasDataLayout,1305 pub fn might_permit_raw_init<C>(self, cx: &C, zero: bool) -> bool 1306 where 1307 Self: Copy, 1308 Ty: TyAbiInterface<'a, C>, 1309 C: HasDataLayout, 1310 { 1311 let scalar_allows_raw_init = move |s: Scalar| -> bool { 1312 if zero { 1313 // The range must contain 0. 1314 s.valid_range.contains(0) 1315 } else { 1316 // The range must include all values. 1317 s.is_always_valid(cx) 1318 } 1319 }; 1320 1321 // Check the ABI. 1322 let valid = match self.abi { 1323 Abi::Uninhabited => false, // definitely UB 1324 Abi::Scalar(s) => scalar_allows_raw_init(s), 1325 Abi::ScalarPair(s1, s2) => scalar_allows_raw_init(s1) && scalar_allows_raw_init(s2), 1326 Abi::Vector { element: s, count } => count == 0 || scalar_allows_raw_init(s), 1327 Abi::Aggregate { .. } => true, // Fields are checked below. 1328 }; 1329 if !valid { 1330 // This is definitely not okay. 1331 return false; 1332 } 1333 1334 // If we have not found an error yet, we need to recursively descend into fields. 1335 match &self.fields { 1336 FieldsShape::Primitive | FieldsShape::Union { .. } => {} 1337 FieldsShape::Array { .. } => { 1338 // FIXME(#66151): For now, we are conservative and do not check arrays. 1339 } 1340 FieldsShape::Arbitrary { offsets, .. } => { 1341 for idx in 0..offsets.len() { 1342 if !self.field(cx, idx).might_permit_raw_init(cx, zero) { 1343 // We found a field that is unhappy with this kind of initialization. 1344 return false; 1345 } 1346 } 1347 } 1348 } 1349 1350 // FIXME(#66151): For now, we are conservative and do not check `self.variants`. 1351 true 1352 } 1353 } 1354