Auto merge of #58413 - Centril:rollup, r=Centril

Rollup of 13 pull requests

Successful merges:

 - #57693 (Doc rewording)
 - #57815 (Speed up the fast path for assert_eq! and assert_ne!)
 - #58034 (Stabilize the time_checked_add feature)
 - #58057 (Stabilize linker-plugin based LTO (aka cross-language LTO))
 - #58137 (Cleanup: rename node_id_to_type(_opt))
 - #58166 (allow shorthand syntax for deprecation reason)
 - #58196 (Add specific feature gate error for const-unstable features)
 - #58200 (fix str mutating through a ptr derived from &self)
 - #58273 (Rename rustc_errors dependency in rust 2018 crates)
 - #58289 (impl iter() for dyn Error)
 - #58387 (Disallow `auto` trait alias syntax)
 - #58404 (use Ubuntu keyserver for CloudABI ports)
 - #58405 (Remove some dead code from libcore)

Failed merges:

r? @ghost

src/ci/docker/dist-various-2/build-cloudabi-toolchain.sh

@@ -32,9 +32,8 @@ ln -s ../lib/llvm-5.0/bin/lld /usr/bin/${target}-ld
 ln -s ../../${target} /usr/lib/llvm-5.0/${target}
 
 # Install the C++ runtime libraries from CloudABI Ports.
-echo deb https://nuxi.nl/distfiles/cloudabi-ports/debian/ cloudabi cloudabi > \
-    /etc/apt/sources.list.d/cloudabi.list
-curl 'https://pgp.mit.edu/pks/lookup?op=get&search=0x0DA51B8531344B15' | \
-    apt-key add -
+apt-key adv --batch --yes --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 0DA51B8531344B15
+add-apt-repository -y 'deb https://nuxi.nl/distfiles/cloudabi-ports/debian/ cloudabi cloudabi'
+
 apt-get update
-apt-get install -y $(echo ${target} | sed -e s/_/-/g)-cxx-runtime
+apt-get install -y "${target//_/-}-cxx-runtime"

src/doc/rustc/src/SUMMARY.md

@@ -13,4 +13,5 @@
 - [Targets](targets/index.md)
     - [Built-in Targets](targets/built-in.md)
     - [Custom Targets](targets/custom.md)
-- [Contributing to `rustc`](contributing.md)
+- [Linker-plugin based LTO](linker-plugin-lto.md)
+- [Contributing to `rustc`](contributing.md)

src/doc/rustc/src/linker-plugin-lto.md

@@ -0,0 +1,108 @@
+# Linker-plugin-LTO
+
+The `-C linker-plugin-lto` flag allows for deferring the LTO optimization
+to the actual linking step, which in turn allows for performing
+interprocedural optimizations across programming language boundaries if
+all the object files being linked were created by LLVM based toolchains.
+The prime example here would be linking Rust code together with
+Clang-compiled C/C++ code.
+
+## Usage
+
+There are two main cases how linker plugin based LTO can be used:
+
+ - compiling a Rust `staticlib` that is used as a C ABI dependency
+ - compiling a Rust binary where `rustc` invokes the linker
+
+In both cases the Rust code has to be compiled with `-C linker-plugin-lto` and
+the C/C++ code with `-flto` or `-flto=thin` so that object files are emitted
+as LLVM bitcode.
+
+### Rust `staticlib` as dependency in C/C++ program
+
+In this case the Rust compiler just has to make sure that the object files in
+the `staticlib` are in the right format. For linking, a linker with the
+LLVM plugin must be used (e.g. LLD).
+
+Using `rustc` directly:
+
+```bash
+# Compile the Rust staticlib
+rustc --crate-type=staticlib -Clinker-plugin-lto -Copt-level=2 ./lib.rs
+# Compile the C code with `-flto=thin`
+clang -c -O2 -flto=thin -o main.o ./main.c
+# Link everything, making sure that we use an appropriate linker
+clang -flto=thin -fuse-ld=lld -L . -l"name-of-your-rust-lib" -o main -O2 ./cmain.o
+```
+
+Using `cargo`:
+
+```bash
+# Compile the Rust staticlib
+RUSTFLAGS="-Clinker-plugin-lto" cargo build --release
+# Compile the C code with `-flto=thin`
+clang -c -O2 -flto=thin -o main.o ./main.c
+# Link everything, making sure that we use an appropriate linker
+clang -flto=thin -fuse-ld=lld -L . -l"name-of-your-rust-lib" -o main -O2 ./cmain.o
+```
+
+### C/C++ code as a dependency in Rust
+
+In this case the linker will be invoked by `rustc`. We again have to make sure
+that an appropriate linker is used.
+
+Using `rustc` directly:
+
+```bash
+# Compile C code with `-flto`
+clang ./clib.c -flto=thin -c -o ./clib.o -O2
+# Create a static library from the C code
+ar crus ./libxyz.a ./clib.o
+
+# Invoke `rustc` with the additional arguments
+rustc -Clinker-plugin-lto -L. -Copt-level=2 -Clinker=clang -Clink-arg=-fuse-ld=lld ./main.rs
+```
+
+Using `cargo` directly:
+
+```bash
+# Compile C code with `-flto`
+clang ./clib.c -flto=thin -c -o ./clib.o -O2
+# Create a static library from the C code
+ar crus ./libxyz.a ./clib.o
+
+# Set the linking arguments via RUSTFLAGS
+RUSTFLAGS="-Clinker-plugin-lto -Clinker=clang -Clink-arg=-fuse-ld=lld" cargo build --release
+```
+
+### Explicitly specifying the linker plugin to be used by `rustc`
+
+If one wants to use a linker other than LLD, the LLVM linker plugin has to be
+specified explicitly. Otherwise the linker cannot read the object files. The
+path to the plugin is passed as an argument to the `-Clinker-plugin-lto`
+option:
+
+```bash
+rustc -Clinker-plugin-lto="/path/to/LLVMgold.so" -L. -Copt-level=2 ./main.rs
+```
+
+
+## Toolchain Compatibility
+
+In order for this kind of LTO to work, the LLVM linker plugin must be able to
+handle the LLVM bitcode produced by both `rustc` and `clang`.
+
+Best results are achieved by using a `rustc` and `clang` that are based on the
+exact same version of LLVM. One can use `rustc -vV` in order to view the LLVM
+used by a given `rustc` version. Note that the version number given
+here is only an approximation as Rust sometimes uses unstable revisions of
+LLVM. However, the approximation is usually reliable.
+
+The following table shows known good combinations of toolchain versions.
+
+|           | Clang 7   | Clang 8   |
+|-----------|-----------|-----------|
+| Rust 1.34 |     ✗     |     ✓     |
+| Rust 1.35 |     ✗     |    ✓(?)   |
+
+Note that the compatibility policy for this feature might change in the future.

src/libcore/lib.rs

@@ -227,20 +227,6 @@ mod unit;
 // `core_arch` depends on libcore, but the contents of this module are
 // set up in such a way that directly pulling it here works such that the
 // crate uses the this crate as its libcore.
-#[allow(unused_macros)]
-macro_rules! test_v16 { ($item:item) => {}; }
-#[allow(unused_macros)]
-macro_rules! test_v32 { ($item:item) => {}; }
-#[allow(unused_macros)]
-macro_rules! test_v64 { ($item:item) => {}; }
-#[allow(unused_macros)]
-macro_rules! test_v128 { ($item:item) => {}; }
-#[allow(unused_macros)]
-macro_rules! test_v256 { ($item:item) => {}; }
-#[allow(unused_macros)]
-macro_rules! test_v512 { ($item:item) => {}; }
-#[allow(unused_macros)]
-macro_rules! vector_impl { ($([$f:ident, $($args:tt)*]),*) => { $($f!($($args)*);)* } }
 #[path = "../stdsimd/crates/core_arch/src/mod.rs"]
 #[allow(missing_docs, missing_debug_implementations, dead_code, unused_imports)]
 #[unstable(feature = "stdsimd", issue = "48556")]

src/libcore/macros.rs

@@ -46,9 +46,12 @@ macro_rules! assert_eq {
         match (&$left, &$right) {
             (left_val, right_val) => {
                 if !(*left_val == *right_val) {
+                    // The reborrows below are intentional. Without them, the stack slot for the
+                    // borrow is initialized even before the values are compared, leading to a
+                    // noticeable slow down.
                     panic!(r#"assertion failed: `(left == right)`
   left: `{:?}`,
- right: `{:?}`"#, left_val, right_val)
+ right: `{:?}`"#, &*left_val, &*right_val)
                 }
             }
         }
@@ -60,9 +63,12 @@ macro_rules! assert_eq {
         match (&($left), &($right)) {
             (left_val, right_val) => {
                 if !(*left_val == *right_val) {
+                    // The reborrows below are intentional. Without them, the stack slot for the
+                    // borrow is initialized even before the values are compared, leading to a
+                    // noticeable slow down.
                     panic!(r#"assertion failed: `(left == right)`
   left: `{:?}`,
- right: `{:?}`: {}"#, left_val, right_val,
+ right: `{:?}`: {}"#, &*left_val, &*right_val,
                            format_args!($($arg)+))
                 }
             }
@@ -97,9 +103,12 @@ macro_rules! assert_ne {
         match (&$left, &$right) {
             (left_val, right_val) => {
                 if *left_val == *right_val {
+                    // The reborrows below are intentional. Without them, the stack slot for the
+                    // borrow is initialized even before the values are compared, leading to a
+                    // noticeable slow down.
                     panic!(r#"assertion failed: `(left != right)`
   left: `{:?}`,
- right: `{:?}`"#, left_val, right_val)
+ right: `{:?}`"#, &*left_val, &*right_val)
                 }
             }
         }
@@ -111,9 +120,12 @@ macro_rules! assert_ne {
         match (&($left), &($right)) {
             (left_val, right_val) => {
                 if *left_val == *right_val {
+                    // The reborrows below are intentional. Without them, the stack slot for the
+                    // borrow is initialized even before the values are compared, leading to a
+                    // noticeable slow down.
                     panic!(r#"assertion failed: `(left != right)`
   left: `{:?}`,
- right: `{:?}`: {}"#, left_val, right_val,
+ right: `{:?}`: {}"#, &*left_val, &*right_val,
                            format_args!($($arg)+))
                 }
             }

src/libcore/str/mod.rs

@@ -1741,9 +1741,9 @@ mod traits {
         }
         #[inline]
         unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output {
-            let ptr = slice.as_ptr().add(self.start);
+            let ptr = slice.as_mut_ptr().add(self.start);
             let len = self.end - self.start;
-            super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr as *mut u8, len))
+            super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, len))
         }
         #[inline]
         fn index(self, slice: &str) -> &Self::Output {
@@ -1805,8 +1805,8 @@ mod traits {
         }
         #[inline]
         unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output {
-            let ptr = slice.as_ptr();
-            super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr as *mut u8, self.end))
+            let ptr = slice.as_mut_ptr();
+            super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, self.end))
         }
         #[inline]
         fn index(self, slice: &str) -> &Self::Output {
@@ -1867,9 +1867,9 @@ mod traits {
         }
         #[inline]
         unsafe fn get_unchecked_mut(self, slice: &mut str) -> &mut Self::Output {
-            let ptr = slice.as_ptr().add(self.start);
+            let ptr = slice.as_mut_ptr().add(self.start);
             let len = slice.len() - self.start;
-            super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr as *mut u8, len))
+            super::from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, len))
         }
         #[inline]
         fn index(self, slice: &str) -> &Self::Output {
@@ -2197,6 +2197,22 @@ impl str {
         self as *const str as *const u8
     }
 
+    /// Converts a mutable string slice to a raw pointer.
+    ///
+    /// As string slices are a slice of bytes, the raw pointer points to a
+    /// [`u8`]. This pointer will be pointing to the first byte of the string
+    /// slice.
+    ///
+    /// It is your responsibility to make sure that the string slice only gets
+    /// modified in a way that it remains valid UTF-8.
+    ///
+    /// [`u8`]: primitive.u8.html
+    #[unstable(feature = "str_as_mut_ptr", issue = "58215")]
+    #[inline]
+    pub fn as_mut_ptr(&mut self) -> *mut u8 {
+        self as *mut str as *mut u8
+    }
+
     /// Returns a subslice of `str`.
     ///
     /// This is the non-panicking alternative to indexing the `str`. Returns
@@ -2484,7 +2500,7 @@ impl str {
         // is_char_boundary checks that the index is in [0, .len()]
         if self.is_char_boundary(mid) {
             let len = self.len();
-            let ptr = self.as_ptr() as *mut u8;
+            let ptr = self.as_mut_ptr();
             unsafe {
                 (from_utf8_unchecked_mut(slice::from_raw_parts_mut(ptr, mid)),
                  from_utf8_unchecked_mut(slice::from_raw_parts_mut(

src/librustc/Cargo.toml

@@ -25,7 +25,7 @@ rustc-rayon-core = "0.1.1"
 rustc_apfloat = { path = "../librustc_apfloat" }
 rustc_target = { path = "../librustc_target" }
 rustc_data_structures = { path = "../librustc_data_structures" }
-rustc_errors = { path = "../librustc_errors" }
+errors = { path = "../librustc_errors", package = "rustc_errors" }
 serialize = { path = "../libserialize" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }

src/librustc/dep_graph/graph.rs

@@ -1,4 +1,4 @@
-use crate::errors::{Diagnostic, DiagnosticBuilder};
+use errors::{Diagnostic, DiagnosticBuilder};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};

src/librustc/hir/lowering.rs

@@ -31,7 +31,6 @@
 //! in the HIR, especially for multiple identifiers.
 
 use crate::dep_graph::DepGraph;
-use crate::errors::Applicability;
 use crate::hir::{self, ParamName};
 use crate::hir::HirVec;
 use crate::hir::map::{DefKey, DefPathData, Definitions};
@@ -41,14 +40,15 @@ use crate::hir::GenericArg;
 use crate::lint::builtin::{self, PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
                     ELIDED_LIFETIMES_IN_PATHS};
 use crate::middle::cstore::CrateStore;
-use rustc_data_structures::fx::FxHashSet;
-use rustc_data_structures::indexed_vec::IndexVec;
-use rustc_data_structures::thin_vec::ThinVec;
-use rustc_data_structures::sync::Lrc;
 use crate::session::Session;
 use crate::session::config::nightly_options;
 use crate::util::common::FN_OUTPUT_NAME;
 use crate::util::nodemap::{DefIdMap, NodeMap};
+use errors::Applicability;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::indexed_vec::IndexVec;
+use rustc_data_structures::thin_vec::ThinVec;
+use rustc_data_structures::sync::Lrc;
 
 use std::collections::{BTreeSet, BTreeMap};
 use std::fmt::Debug;

src/librustc/hir/mod.rs

@@ -10,12 +10,12 @@ pub use self::PrimTy::*;
 pub use self::UnOp::*;
 pub use self::UnsafeSource::*;
 
-use crate::errors::FatalError;
 use crate::hir::def::Def;
 use crate::hir::def_id::{DefId, DefIndex, LocalDefId, CRATE_DEF_INDEX};
 use crate::util::nodemap::{NodeMap, FxHashSet};
 use crate::mir::mono::Linkage;
 
+use errors::FatalError;
 use syntax_pos::{Span, DUMMY_SP, symbol::InternedString};
 use syntax::source_map::Spanned;
 use rustc_target::spec::abi::Abi;

src/librustc/infer/error_reporting/mod.rs

@@ -50,16 +50,16 @@ use super::region_constraints::GenericKind;
 use super::{InferCtxt, RegionVariableOrigin, SubregionOrigin, TypeTrace, ValuePairs};
 use crate::infer::{self, SuppressRegionErrors};
 
-use crate::errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
 use crate::hir;
 use crate::hir::def_id::DefId;
 use crate::hir::Node;
 use crate::middle::region;
-use std::{cmp, fmt};
-use syntax_pos::{Pos, Span};
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use crate::ty::error::TypeError;
 use crate::ty::{self, subst::Subst, Region, Ty, TyCtxt, TyKind, TypeFoldable};
+use errors::{Applicability, DiagnosticBuilder, DiagnosticStyledString};
+use std::{cmp, fmt};
+use syntax_pos::{Pos, Span};
 
 mod note;
 

src/librustc/infer/error_reporting/need_type_info.rs

@@ -5,7 +5,7 @@ use crate::infer::type_variable::TypeVariableOrigin;
 use crate::ty::{self, Ty, Infer, TyVar};
 use syntax::source_map::CompilerDesugaringKind;
 use syntax_pos::Span;
-use crate::errors::DiagnosticBuilder;
+use errors::DiagnosticBuilder;
 
 struct FindLocalByTypeVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
     infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
@@ -16,9 +16,9 @@ struct FindLocalByTypeVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
 }
 
 impl<'a, 'gcx, 'tcx> FindLocalByTypeVisitor<'a, 'gcx, 'tcx> {
-    fn node_matches_type(&mut self, node_id: HirId) -> bool {
+    fn node_matches_type(&mut self, hir_id: HirId) -> bool {
         let ty_opt = self.infcx.in_progress_tables.and_then(|tables| {
-            tables.borrow().node_id_to_type_opt(node_id)
+            tables.borrow().node_type_opt(hir_id)
         });
         match ty_opt {
             Some(ty) => {

src/librustc/infer/error_reporting/nice_region_error/named_anon_conflict.rs

@@ -3,7 +3,7 @@
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::ty;
 use crate::util::common::ErrorReported;
-use crate::errors::Applicability;
+use errors::Applicability;
 
 impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
     /// When given a `ConcreteFailure` for a function with arguments containing a named region and

src/librustc/infer/error_reporting/nice_region_error/placeholder_error.rs

@@ -1,4 +1,4 @@
-use crate::errors::DiagnosticBuilder;
+use errors::DiagnosticBuilder;
 use crate::hir::def_id::DefId;
 use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError;

src/librustc/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -4,7 +4,7 @@ use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::lexical_region_resolve::RegionResolutionError;
 use crate::ty::{BoundRegion, FreeRegion, RegionKind};
 use crate::util::common::ErrorReported;
-use crate::errors::Applicability;
+use errors::Applicability;
 
 impl<'a, 'gcx, 'tcx> NiceRegionError<'a, 'gcx, 'tcx> {
     /// Print the error message for lifetime errors when the return type is a static impl Trait.