diff --git a/compiler/rustc_metadata/src/rmeta/table.rs b/compiler/rustc_metadata/src/rmeta/table.rs index e906c906347..35987072ed6 100644 --- a/compiler/rustc_metadata/src/rmeta/table.rs +++ b/compiler/rustc_metadata/src/rmeta/table.rs @@ -5,7 +5,6 @@ use rustc_index::Idx; use rustc_middle::ty::{ParameterizedOverTcx, UnusedGenericParams}; use rustc_serialize::opaque::FileEncoder; -use rustc_serialize::Encoder as _; use rustc_span::hygiene::MacroKind; use std::marker::PhantomData; use std::num::NonZeroUsize; @@ -468,7 +467,10 @@ pub(crate) fn encode(&self, buf: &mut FileEncoder) -> LazyTable { let width = self.width; for block in &self.blocks { - buf.emit_raw_bytes(&block[..width]); + buf.write_with(|dest| { + *dest = *block; + width + }); } LazyTable::from_position_and_encoded_size( diff --git a/compiler/rustc_query_system/src/dep_graph/serialized.rs b/compiler/rustc_query_system/src/dep_graph/serialized.rs index 4ba0cb31d0b..3fd83f79a48 100644 --- a/compiler/rustc_query_system/src/dep_graph/serialized.rs +++ b/compiler/rustc_query_system/src/dep_graph/serialized.rs @@ -394,7 +394,10 @@ struct NodeInfo { impl Encodable for NodeInfo { fn encode(&self, e: &mut FileEncoder) { let header = SerializedNodeHeader::new(self); - e.emit_raw_bytes(&header.bytes); + e.write_with(|dest| { + *dest = header.bytes; + header.bytes.len() + }); if header.len().is_none() { e.emit_usize(self.edges.len()); @@ -402,8 +405,10 @@ fn encode(&self, e: &mut FileEncoder) { let bytes_per_index = header.bytes_per_index(); for node_index in self.edges.iter() { - let bytes = node_index.as_u32().to_le_bytes(); - e.emit_raw_bytes(&bytes[..bytes_per_index]); + e.write_with(|dest| { + *dest = node_index.as_u32().to_le_bytes(); + bytes_per_index + }); } } } diff --git a/compiler/rustc_serialize/src/leb128.rs b/compiler/rustc_serialize/src/leb128.rs index e568b9e6786..ca661bac78c 100644 --- a/compiler/rustc_serialize/src/leb128.rs +++ b/compiler/rustc_serialize/src/leb128.rs @@ -15,23 +15,20 @@ pub const fn largest_max_leb128_len() -> usize { macro_rules! impl_write_unsigned_leb128 { ($fn_name:ident, $int_ty:ty) => { #[inline] - pub fn $fn_name( - out: &mut [::std::mem::MaybeUninit; max_leb128_len::<$int_ty>()], - mut value: $int_ty, - ) -> &[u8] { + pub fn $fn_name(out: &mut [u8; max_leb128_len::<$int_ty>()], mut value: $int_ty) -> usize { let mut i = 0; loop { if value < 0x80 { unsafe { - *out.get_unchecked_mut(i).as_mut_ptr() = value as u8; + *out.get_unchecked_mut(i) = value as u8; } i += 1; break; } else { unsafe { - *out.get_unchecked_mut(i).as_mut_ptr() = ((value & 0x7f) | 0x80) as u8; + *out.get_unchecked_mut(i) = ((value & 0x7f) | 0x80) as u8; } value >>= 7; @@ -39,7 +36,7 @@ pub fn $fn_name( } } - unsafe { ::std::mem::MaybeUninit::slice_assume_init_ref(&out.get_unchecked(..i)) } + i } }; } @@ -87,10 +84,7 @@ pub fn $fn_name(decoder: &mut MemDecoder<'_>) -> $int_ty { macro_rules! impl_write_signed_leb128 { ($fn_name:ident, $int_ty:ty) => { #[inline] - pub fn $fn_name( - out: &mut [::std::mem::MaybeUninit; max_leb128_len::<$int_ty>()], - mut value: $int_ty, - ) -> &[u8] { + pub fn $fn_name(out: &mut [u8; max_leb128_len::<$int_ty>()], mut value: $int_ty) -> usize { let mut i = 0; loop { @@ -104,7 +98,7 @@ pub fn $fn_name( } unsafe { - *out.get_unchecked_mut(i).as_mut_ptr() = byte; + *out.get_unchecked_mut(i) = byte; } i += 1; @@ -114,7 +108,7 @@ pub fn $fn_name( } } - unsafe { ::std::mem::MaybeUninit::slice_assume_init_ref(&out.get_unchecked(..i)) } + i } }; } diff --git a/compiler/rustc_serialize/src/lib.rs b/compiler/rustc_serialize/src/lib.rs index ce8503918b4..dd40b3cf028 100644 --- a/compiler/rustc_serialize/src/lib.rs +++ b/compiler/rustc_serialize/src/lib.rs @@ -17,6 +17,9 @@ #![feature(new_uninit)] #![feature(allocator_api)] #![feature(ptr_sub_ptr)] +#![feature(slice_first_last_chunk)] +#![feature(inline_const)] +#![feature(const_option)] #![cfg_attr(test, feature(test))] #![allow(rustc::internal)] #![deny(rustc::untranslatable_diagnostic)] diff --git a/compiler/rustc_serialize/src/opaque.rs b/compiler/rustc_serialize/src/opaque.rs index f1b7e8d9ae0..fcd35f2ea57 100644 --- a/compiler/rustc_serialize/src/opaque.rs +++ b/compiler/rustc_serialize/src/opaque.rs @@ -3,10 +3,8 @@ use std::fs::File; use std::io::{self, Write}; use std::marker::PhantomData; -use std::mem::MaybeUninit; use std::ops::Range; use std::path::Path; -use std::ptr; // ----------------------------------------------------------------------------- // Encoder @@ -24,10 +22,9 @@ /// size of the buffer, rather than the full length of the encoded data, and /// because it doesn't need to reallocate memory along the way. pub struct FileEncoder { - /// The input buffer. For adequate performance, we need more control over - /// buffering than `BufWriter` offers. If `BufWriter` ever offers a raw - /// buffer access API, we can use it, and remove `buf` and `buffered`. - buf: Box<[MaybeUninit]>, + /// The input buffer. For adequate performance, we need to be able to write + /// directly to the unwritten region of the buffer, without calling copy_from_slice. + buf: Box<[u8; BUF_SIZE]>, buffered: usize, flushed: usize, file: File, @@ -38,15 +35,11 @@ pub struct FileEncoder { impl FileEncoder { pub fn new>(path: P) -> io::Result { - // Create the file for reading and writing, because some encoders do both - // (e.g. the metadata encoder when -Zmeta-stats is enabled) - let file = File::options().read(true).write(true).create(true).truncate(true).open(path)?; - Ok(FileEncoder { - buf: Box::new_uninit_slice(BUF_SIZE), + buf: vec![0u8; BUF_SIZE].into_boxed_slice().try_into().unwrap(), buffered: 0, flushed: 0, - file, + file: File::create(path)?, res: Ok(()), }) } @@ -54,94 +47,20 @@ pub fn new>(path: P) -> io::Result { #[inline] pub fn position(&self) -> usize { // Tracking position this way instead of having a `self.position` field - // means that we don't have to update the position on every write call. + // means that we only need to update `self.buffered` on a write call, + // as opposed to updating `self.position` and `self.buffered`. self.flushed + self.buffered } - pub fn flush(&mut self) { - // This is basically a copy of `BufWriter::flush`. If `BufWriter` ever - // offers a raw buffer access API, we can use it, and remove this. - - /// Helper struct to ensure the buffer is updated after all the writes - /// are complete. It tracks the number of written bytes and drains them - /// all from the front of the buffer when dropped. - struct BufGuard<'a> { - buffer: &'a mut [u8], - encoder_buffered: &'a mut usize, - encoder_flushed: &'a mut usize, - flushed: usize, - } - - impl<'a> BufGuard<'a> { - fn new( - buffer: &'a mut [u8], - encoder_buffered: &'a mut usize, - encoder_flushed: &'a mut usize, - ) -> Self { - assert_eq!(buffer.len(), *encoder_buffered); - Self { buffer, encoder_buffered, encoder_flushed, flushed: 0 } - } - - /// The unwritten part of the buffer - fn remaining(&self) -> &[u8] { - &self.buffer[self.flushed..] - } - - /// Flag some bytes as removed from the front of the buffer - fn consume(&mut self, amt: usize) { - self.flushed += amt; - } - - /// true if all of the bytes have been written - fn done(&self) -> bool { - self.flushed >= *self.encoder_buffered - } - } - - impl Drop for BufGuard<'_> { - fn drop(&mut self) { - if self.flushed > 0 { - if self.done() { - *self.encoder_flushed += *self.encoder_buffered; - *self.encoder_buffered = 0; - } else { - self.buffer.copy_within(self.flushed.., 0); - *self.encoder_flushed += self.flushed; - *self.encoder_buffered -= self.flushed; - } - } - } - } - - // If we've already had an error, do nothing. It'll get reported after - // `finish` is called. - if self.res.is_err() { - return; - } - - let mut guard = BufGuard::new( - unsafe { MaybeUninit::slice_assume_init_mut(&mut self.buf[..self.buffered]) }, - &mut self.buffered, - &mut self.flushed, - ); - - while !guard.done() { - match self.file.write(guard.remaining()) { - Ok(0) => { - self.res = Err(io::Error::new( - io::ErrorKind::WriteZero, - "failed to write the buffered data", - )); - return; - } - Ok(n) => guard.consume(n), - Err(ref e) if e.kind() == io::ErrorKind::Interrupted => {} - Err(e) => { - self.res = Err(e); - return; - } - } + #[cold] + #[inline(never)] + pub fn flush(&mut self) -> &mut [u8; BUF_SIZE] { + if self.res.is_ok() { + self.res = self.file.write_all(&self.buf[..self.buffered]); } + self.flushed += self.buffered; + self.buffered = 0; + &mut self.buf } pub fn file(&self) -> &File { @@ -149,99 +68,64 @@ pub fn file(&self) -> &File { } #[inline] - fn write_one(&mut self, value: u8) { - let mut buffered = self.buffered; + fn buffer_empty(&mut self) -> &mut [u8] { + // SAFETY: self.buffered is inbounds as an invariant of the type + unsafe { self.buf.get_unchecked_mut(self.buffered..) } + } - if std::intrinsics::unlikely(buffered + 1 > BUF_SIZE) { - self.flush(); - buffered = 0; + #[cold] + #[inline(never)] + fn write_all_cold_path(&mut self, buf: &[u8]) { + if let Some(dest) = self.flush().get_mut(..buf.len()) { + dest.copy_from_slice(buf); + self.buffered += buf.len(); + } else { + if self.res.is_ok() { + self.res = self.file.write_all(buf); + } + self.flushed += buf.len(); } - - // SAFETY: The above check and `flush` ensures that there is enough - // room to write the input to the buffer. - unsafe { - *MaybeUninit::slice_as_mut_ptr(&mut self.buf).add(buffered) = value; - } - - self.buffered = buffered + 1; } #[inline] fn write_all(&mut self, buf: &[u8]) { - let buf_len = buf.len(); - - if std::intrinsics::likely(buf_len <= BUF_SIZE) { - let mut buffered = self.buffered; - - if std::intrinsics::unlikely(buffered + buf_len > BUF_SIZE) { - self.flush(); - buffered = 0; - } - - // SAFETY: The above check and `flush` ensures that there is enough - // room to write the input to the buffer. - unsafe { - let src = buf.as_ptr(); - let dst = MaybeUninit::slice_as_mut_ptr(&mut self.buf).add(buffered); - ptr::copy_nonoverlapping(src, dst, buf_len); - } - - self.buffered = buffered + buf_len; + if let Some(dest) = self.buffer_empty().get_mut(..buf.len()) { + dest.copy_from_slice(buf); + self.buffered += buf.len(); } else { - self.write_all_unbuffered(buf); + self.write_all_cold_path(buf); } } - fn write_all_unbuffered(&mut self, mut buf: &[u8]) { - // If we've already had an error, do nothing. It'll get reported after - // `finish` is called. - if self.res.is_err() { - return; - } - - if self.buffered > 0 { + /// Write up to `N` bytes to this encoder. + /// + /// Whenever possible, use this function to do writes whose length has a small and + /// compile-time constant upper bound. + #[inline] + pub fn write_with(&mut self, mut visitor: V) + where + V: FnMut(&mut [u8; N]) -> usize, + { + let flush_threshold = const { BUF_SIZE.checked_sub(N).unwrap() }; + if std::intrinsics::unlikely(self.buffered > flush_threshold) { self.flush(); } - - // This is basically a copy of `Write::write_all` but also updates our - // `self.flushed`. It's necessary because `Write::write_all` does not - // return the number of bytes written when an error is encountered, and - // without that, we cannot accurately update `self.flushed` on error. - while !buf.is_empty() { - match self.file.write(buf) { - Ok(0) => { - self.res = Err(io::Error::new( - io::ErrorKind::WriteZero, - "failed to write whole buffer", - )); - return; - } - Ok(n) => { - buf = &buf[n..]; - self.flushed += n; - } - Err(ref e) if e.kind() == io::ErrorKind::Interrupted => {} - Err(e) => { - self.res = Err(e); - return; - } - } - } + // SAFETY: We checked above that that N < self.buffer_empty().len(), + // and if isn't, flush ensures that our empty buffer is now BUF_SIZE. + // We produce a post-mono error if N > BUF_SIZE. + let buf = unsafe { self.buffer_empty().first_chunk_mut::().unwrap_unchecked() }; + let written = visitor(buf); + debug_assert!(written <= N); + // We have to ensure that an errant visitor cannot cause self.buffered to exeed BUF_SIZE. + self.buffered += written.min(N); } pub fn finish(mut self) -> Result { self.flush(); - - let res = std::mem::replace(&mut self.res, Ok(())); - res.map(|()| self.position()) - } -} - -impl Drop for FileEncoder { - fn drop(&mut self) { - // Likely to be a no-op, because `finish` should have been called and - // it also flushes. But do it just in case. - let _result = self.flush(); + match self.res { + Ok(()) => Ok(self.position()), + Err(e) => Err(e), + } } } @@ -250,25 +134,7 @@ macro_rules! write_leb128 { #[inline] fn $this_fn(&mut self, v: $int_ty) { const MAX_ENCODED_LEN: usize = $crate::leb128::max_leb128_len::<$int_ty>(); - - let mut buffered = self.buffered; - - // This can't overflow because BUF_SIZE and MAX_ENCODED_LEN are both - // quite small. - if std::intrinsics::unlikely(buffered + MAX_ENCODED_LEN > BUF_SIZE) { - self.flush(); - buffered = 0; - } - - // SAFETY: The above check and flush ensures that there is enough - // room to write the encoded value to the buffer. - let buf = unsafe { - &mut *(self.buf.as_mut_ptr().add(buffered) - as *mut [MaybeUninit; MAX_ENCODED_LEN]) - }; - - let encoded = leb128::$write_leb_fn(buf, v); - self.buffered = buffered + encoded.len(); + self.write_with::(|buf| leb128::$write_leb_fn(buf, v)) } }; } @@ -281,12 +147,18 @@ impl Encoder for FileEncoder { #[inline] fn emit_u16(&mut self, v: u16) { - self.write_all(&v.to_le_bytes()); + self.write_with(|buf| { + *buf = v.to_le_bytes(); + 2 + }); } #[inline] fn emit_u8(&mut self, v: u8) { - self.write_one(v); + self.write_with(|buf: &mut [u8; 1]| { + buf[0] = v; + 1 + }); } write_leb128!(emit_isize, isize, write_isize_leb128); @@ -296,7 +168,10 @@ fn emit_u8(&mut self, v: u8) { #[inline] fn emit_i16(&mut self, v: i16) { - self.write_all(&v.to_le_bytes()); + self.write_with(|buf| { + *buf = v.to_le_bytes(); + 2 + }); } #[inline] @@ -495,7 +370,10 @@ impl Encodable for IntEncodedWithFixedSize { #[inline] fn encode(&self, e: &mut FileEncoder) { let _start_pos = e.position(); - e.emit_raw_bytes(&self.0.to_le_bytes()); + e.write_with(|buf| { + *buf = self.0.to_le_bytes(); + buf.len() + }); let _end_pos = e.position(); debug_assert_eq!((_end_pos - _start_pos), IntEncodedWithFixedSize::ENCODED_SIZE); } diff --git a/compiler/rustc_serialize/tests/leb128.rs b/compiler/rustc_serialize/tests/leb128.rs index 7872e778431..dc9b32a968b 100644 --- a/compiler/rustc_serialize/tests/leb128.rs +++ b/compiler/rustc_serialize/tests/leb128.rs @@ -1,8 +1,4 @@ -#![feature(maybe_uninit_slice)] -#![feature(maybe_uninit_uninit_array)] - use rustc_serialize::leb128::*; -use std::mem::MaybeUninit; use rustc_serialize::Decoder; macro_rules! impl_test_unsigned_leb128 { @@ -24,9 +20,10 @@ fn $test_name() { let mut stream = Vec::new(); + let mut buf = Default::default(); for &x in &values { - let mut buf = MaybeUninit::uninit_array(); - stream.extend($write_fn_name(&mut buf, x)); + let n = $write_fn_name(&mut buf, x); + stream.extend(&buf[..n]); } let mut decoder = rustc_serialize::opaque::MemDecoder::new(&stream, 0); @@ -70,9 +67,10 @@ fn $test_name() { let mut stream = Vec::new(); + let mut buf = Default::default(); for &x in &values { - let mut buf = MaybeUninit::uninit_array(); - stream.extend($write_fn_name(&mut buf, x)); + let n = $write_fn_name(&mut buf, x); + stream.extend(&buf[..n]); } let mut decoder = rustc_serialize::opaque::MemDecoder::new(&stream, 0);