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Miri: rename "undef" to "uninit"
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renamed Allocation::check_defined_and_ptr to Allocation::check_init_and_ptr

renamed Allocation::check_defined_and_ptr to Allocation::check_init_and_ptr

in src/librustc_middle/mir/interpret/allocation.rs

renamed Allocation::is_defined and Allocation::check_defined, fixed documentation

renamed Allocation::is_defined and Allocation::check_defined to is_init and check_init respectively.

Fixed documentation so it correctly refers to "initialization" instead of "defined"-ness

renamed Allocation::mark_definedness

renamed Allocation::mark_definedness to Allocation::mark_init

Renamed new_state parameter in Allocation::mark_init

Renamed new_state to is_init, as the latter is more descriptive.

renamed functions in AllocationDefinedness

renamed AllocationDefinedness::all_bytes_undef and AllocationDefinedness::mark_compressed_undef_range to no_bytes_init and mark_compressed_init_range respectively.

renamed AllocationDefinedness to InitMaskCompressed

renamed Immediate::to_scalar_or_undef

renamed to to_scalar_or_uninit

fixed comment references to "undef"

Changed comments referring to "undef" and "definedness" to "initialization" and "initialization state" in src/librustc_mir/interpret/memory.rs and src/librustc_middle/mir/interpret/allocation.rs

changed references to "undef" in comments and a variable

Changed some comments referring to "undef" to use "uninitialized" instead. Also changed a variable from "undef_end" to "uninit_end".
All changes were made within src/librustc_middle/mir/interpret/allocation.rs.

Changed more comments referring to undef

Changed comments to use "uninitialized" instead of "undef" in src/librustc_middle/mir/interpret/allocation.rs.
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@pnadon
pnadon committed Jul 25, 2020
1 parent 55984b6 commit ef9c4f5
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94 changes: 47 additions & 47 deletions src/librustc_middle/mir/interpret/allocation.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -105,7 +105,7 @@ impl<Tag> Allocation<Tag> {
Allocation::from_bytes(slice, Align::from_bytes(1).unwrap())
}

pub fn undef(size: Size, align: Align) -> Self {
pub fn uninit(size: Size, align: Align) -> Self {
Allocation {
bytes: vec![0; size.bytes_usize()],
relocations: Relocations::new(),
Expand Down Expand Up @@ -153,7 +153,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
self.size.bytes_usize()
}

/// Looks at a slice which may describe undefined bytes or describe a relocation. This differs
/// Looks at a slice which may describe uninitialized bytes or describe a relocation. This differs
/// from `get_bytes_with_undef_and_ptr` in that it does no relocation checks (even on the
/// edges) at all. It further ignores `AllocationExtra` callbacks.
/// This must not be used for reads affecting the interpreter execution.
Expand Down Expand Up @@ -192,7 +192,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
offset.bytes_usize()..end
}

/// The last argument controls whether we error out when there are undefined
/// The last argument controls whether we error out when there are uninitialized
/// or pointer bytes. You should never call this, call `get_bytes` or
/// `get_bytes_with_undef_and_ptr` instead,
///
Expand All @@ -206,12 +206,12 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
cx: &impl HasDataLayout,
ptr: Pointer<Tag>,
size: Size,
check_defined_and_ptr: bool,
check_init_and_ptr: bool,
) -> InterpResult<'tcx, &[u8]> {
let range = self.check_bounds(ptr.offset, size);

if check_defined_and_ptr {
self.check_defined(ptr, size)?;
if check_init_and_ptr {
self.check_init(ptr, size)?;
self.check_relocations(cx, ptr, size)?;
} else {
// We still don't want relocations on the *edges*.
Expand Down Expand Up @@ -239,7 +239,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
self.get_bytes_internal(cx, ptr, size, true)
}

/// It is the caller's responsibility to handle undefined and pointer bytes.
/// It is the caller's responsibility to handle uninitialized and pointer bytes.
/// However, this still checks that there are no relocations on the *edges*.
///
/// It is the caller's responsibility to check bounds and alignment beforehand.
Expand Down Expand Up @@ -267,7 +267,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
) -> InterpResult<'tcx, &mut [u8]> {
let range = self.check_bounds(ptr.offset, size);

self.mark_definedness(ptr, size, true);
self.mark_init(ptr, size, true);
self.clear_relocations(cx, ptr, size)?;

AllocationExtra::memory_written(self, ptr, size)?;
Expand Down Expand Up @@ -303,7 +303,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {

/// Validates that `ptr.offset` and `ptr.offset + size` do not point to the middle of a
/// relocation. If `allow_ptr_and_undef` is `false`, also enforces that the memory in the
/// given range contains neither relocations nor undef bytes.
/// given range contains neither relocations nor uninitialized bytes.
pub fn check_bytes(
&self,
cx: &impl HasDataLayout,
Expand All @@ -313,9 +313,9 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
) -> InterpResult<'tcx> {
// Check bounds and relocations on the edges.
self.get_bytes_with_undef_and_ptr(cx, ptr, size)?;
// Check undef and ptr.
// Check uninit and ptr.
if !allow_ptr_and_undef {
self.check_defined(ptr, size)?;
self.check_init(ptr, size)?;
self.check_relocations(cx, ptr, size)?;
}
Ok(())
Expand Down Expand Up @@ -364,7 +364,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
let bytes = self.get_bytes_with_undef_and_ptr(cx, ptr, size)?;
// Uninit check happens *after* we established that the alignment is correct.
// We must not return `Ok()` for unaligned pointers!
if self.is_defined(ptr, size).is_err() {
if self.is_init(ptr, size).is_err() {
// This inflates uninitialized bytes to the entire scalar, even if only a few
// bytes are uninitialized.
return Ok(ScalarMaybeUninit::Uninit);
Expand Down Expand Up @@ -416,7 +416,7 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
let val = match val {
ScalarMaybeUninit::Scalar(scalar) => scalar,
ScalarMaybeUninit::Uninit => {
self.mark_definedness(ptr, type_size, false);
self.mark_init(ptr, type_size, false);
return Ok(());
}
};
Expand Down Expand Up @@ -512,7 +512,7 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
let start = ptr.offset;
let end = start + size; // `Size` addition

// Mark parts of the outermost relocations as undefined if they partially fall outside the
// Mark parts of the outermost relocations as uninitialized if they partially fall outside the
// given range.
if first < start {
self.init_mask.set_range(first, start, false);
Expand Down Expand Up @@ -542,20 +542,20 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
}
}

/// Undefined bytes.
/// Uninitialized bytes.
impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
/// Checks whether the given range is entirely defined.
/// Checks whether the given range is entirely initialized.
///
/// Returns `Ok(())` if it's defined. Otherwise returns the range of byte
/// indexes of the first contiguous undefined access.
fn is_defined(&self, ptr: Pointer<Tag>, size: Size) -> Result<(), Range<Size>> {
/// Returns `Ok(())` if it's initialized. Otherwise returns the range of byte
/// indexes of the first contiguous uninitialized access.
fn is_init(&self, ptr: Pointer<Tag>, size: Size) -> Result<(), Range<Size>> {
self.init_mask.is_range_initialized(ptr.offset, ptr.offset + size) // `Size` addition
}

/// Checks that a range of bytes is defined. If not, returns the `InvalidUndefBytes`
/// error which will report the first range of bytes which is undefined.
fn check_defined(&self, ptr: Pointer<Tag>, size: Size) -> InterpResult<'tcx> {
self.is_defined(ptr, size).or_else(|idx_range| {
/// Checks that a range of bytes is initialized. If not, returns the `InvalidUninitBytes`
/// error which will report the first range of bytes which is uninitialized.
fn check_init(&self, ptr: Pointer<Tag>, size: Size) -> InterpResult<'tcx> {
self.is_init(ptr, size).or_else(|idx_range| {
throw_ub!(InvalidUninitBytes(Some(Box::new(UninitBytesAccess {
access_ptr: ptr.erase_tag(),
access_size: size,
Expand All @@ -565,44 +565,44 @@ impl<'tcx, Tag: Copy, Extra> Allocation<Tag, Extra> {
})
}

pub fn mark_definedness(&mut self, ptr: Pointer<Tag>, size: Size, new_state: bool) {
pub fn mark_init(&mut self, ptr: Pointer<Tag>, size: Size, is_init: bool) {
if size.bytes() == 0 {
return;
}
self.init_mask.set_range(ptr.offset, ptr.offset + size, new_state);
self.init_mask.set_range(ptr.offset, ptr.offset + size, is_init);
}
}

/// Run-length encoding of the undef mask.
/// Run-length encoding of the uninit mask.
/// Used to copy parts of a mask multiple times to another allocation.
pub struct AllocationDefinedness {
/// The definedness of the first range.
pub struct InitMaskCompressed {
/// Whether the first range is initialized.
initial: bool,
/// The lengths of ranges that are run-length encoded.
/// The definedness of the ranges alternate starting with `initial`.
/// The initialization state of the ranges alternate starting with `initial`.
ranges: smallvec::SmallVec<[u64; 1]>,
}

impl AllocationDefinedness {
pub fn all_bytes_undef(&self) -> bool {
// The `ranges` are run-length encoded and of alternating definedness.
// So if `ranges.len() > 1` then the second block is a range of defined.
impl InitMaskCompressed {
pub fn no_bytes_init(&self) -> bool {
// The `ranges` are run-length encoded and of alternating initialization state.
// So if `ranges.len() > 1` then the second block is an initialized range.
!self.initial && self.ranges.len() == 1
}
}

/// Transferring the definedness mask to other allocations.
/// Transferring the initialization mask to other allocations.
impl<Tag, Extra> Allocation<Tag, Extra> {
/// Creates a run-length encoding of the undef mask.
pub fn compress_undef_range(&self, src: Pointer<Tag>, size: Size) -> AllocationDefinedness {
/// Creates a run-length encoding of the initialization mask.
pub fn compress_undef_range(&self, src: Pointer<Tag>, size: Size) -> InitMaskCompressed {
// Since we are copying `size` bytes from `src` to `dest + i * size` (`for i in 0..repeat`),
// a naive undef mask copying algorithm would repeatedly have to read the undef mask from
// a naive initialization mask copying algorithm would repeatedly have to read the initialization mask from
// the source and write it to the destination. Even if we optimized the memory accesses,
// we'd be doing all of this `repeat` times.
// Therefore we precompute a compressed version of the undef mask of the source value and
// Therefore we precompute a compressed version of the initialization mask of the source value and
// then write it back `repeat` times without computing any more information from the source.

// A precomputed cache for ranges of defined/undefined bits
// A precomputed cache for ranges of initialized / uninitialized bits
// 0000010010001110 will become
// `[5, 1, 2, 1, 3, 3, 1]`,
// where each element toggles the state.
Expand All @@ -613,7 +613,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
let mut cur = initial;

for i in 1..size.bytes() {
// FIXME: optimize to bitshift the current undef block's bits and read the top bit.
// FIXME: optimize to bitshift the current uninitialized block's bits and read the top bit.
if self.init_mask.get(src.offset + Size::from_bytes(i)) == cur {
cur_len += 1;
} else {
Expand All @@ -625,13 +625,13 @@ impl<Tag, Extra> Allocation<Tag, Extra> {

ranges.push(cur_len);

AllocationDefinedness { ranges, initial }
InitMaskCompressed { ranges, initial }
}

/// Applies multiple instances of the run-length encoding to the undef mask.
pub fn mark_compressed_undef_range(
/// Applies multiple instances of the run-length encoding to the initialization mask.
pub fn mark_compressed_init_range(
&mut self,
defined: &AllocationDefinedness,
defined: &InitMaskCompressed,
dest: Pointer<Tag>,
size: Size,
repeat: u64,
Expand Down Expand Up @@ -740,7 +740,7 @@ impl<Tag: Copy, Extra> Allocation<Tag, Extra> {
}

////////////////////////////////////////////////////////////////////////////////
// Undefined byte tracking
// Uninitialized byte tracking
////////////////////////////////////////////////////////////////////////////////

type Block = u64;
Expand Down Expand Up @@ -778,11 +778,11 @@ impl InitMask {

match idx {
Some(idx) => {
let undef_end = (idx.bytes()..end.bytes())
let uninit_end = (idx.bytes()..end.bytes())
.map(Size::from_bytes)
.find(|&i| self.get(i))
.unwrap_or(end);
Err(idx..undef_end)
Err(idx..uninit_end)
}
None => Ok(()),
}
Expand Down
18 changes: 9 additions & 9 deletions src/librustc_mir/interpret/memory.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -171,7 +171,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
align: Align,
kind: MemoryKind<M::MemoryKind>,
) -> Pointer<M::PointerTag> {
let alloc = Allocation::undef(size, align);
let alloc = Allocation::uninit(size, align);
self.allocate_with(alloc, kind)
}

Expand Down Expand Up @@ -904,18 +904,18 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {

let dest_bytes = dest_bytes.as_mut_ptr();

// Prepare a copy of the undef mask.
// Prepare a copy of the initialization mask.
let compressed = self.get_raw(src.alloc_id)?.compress_undef_range(src, size);

if compressed.all_bytes_undef() {
// Fast path: If all bytes are `undef` then there is nothing to copy. The target range
// is marked as undef but we otherwise omit changing the byte representation which may
// be arbitrary for undef bytes.
if compressed.no_bytes_init() {
// Fast path: If all bytes are `uninit` then there is nothing to copy. The target range
// is marked as unititialized but we otherwise omit changing the byte representation which may
// be arbitrary for uninitialized bytes.
// This also avoids writing to the target bytes so that the backing allocation is never
// touched if the bytes stay undef for the whole interpreter execution. On contemporary
// touched if the bytes stay uninitialized for the whole interpreter execution. On contemporary
// operating system this can avoid physically allocating the page.
let dest_alloc = self.get_raw_mut(dest.alloc_id)?;
dest_alloc.mark_definedness(dest, size * length, false); // `Size` multiplication
dest_alloc.mark_init(dest, size * length, false); // `Size` multiplication
dest_alloc.mark_relocation_range(relocations);
return Ok(());
}
Expand Down Expand Up @@ -955,7 +955,7 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
}

// now fill in all the data
self.get_raw_mut(dest.alloc_id)?.mark_compressed_undef_range(
self.get_raw_mut(dest.alloc_id)?.mark_compressed_init_range(
&compressed,
dest,
size,
Expand Down
6 changes: 3 additions & 3 deletions src/librustc_mir/interpret/operand.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -63,7 +63,7 @@ impl<'tcx, Tag> Immediate<Tag> {
}

#[inline]
pub fn to_scalar_or_undef(self) -> ScalarMaybeUninit<Tag> {
pub fn to_scalar_or_uninit(self) -> ScalarMaybeUninit<Tag> {
match self {
Immediate::Scalar(val) => val,
Immediate::ScalarPair(..) => bug!("Got a wide pointer where a scalar was expected"),
Expand All @@ -72,7 +72,7 @@ impl<'tcx, Tag> Immediate<Tag> {

#[inline]
pub fn to_scalar(self) -> InterpResult<'tcx, Scalar<Tag>> {
self.to_scalar_or_undef().check_init()
self.to_scalar_or_uninit().check_init()
}

#[inline]
Expand Down Expand Up @@ -333,7 +333,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
&self,
op: OpTy<'tcx, M::PointerTag>,
) -> InterpResult<'tcx, ScalarMaybeUninit<M::PointerTag>> {
Ok(self.read_immediate(op)?.to_scalar_or_undef())
Ok(self.read_immediate(op)?.to_scalar_or_uninit())
}

// Turn the wide MPlace into a string (must already be dereferenced!)
Expand Down

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