Auto merge of #52958 - pietroalbini:rollup, r=pietroalbini

Rollup of 15 pull requests

Successful merges:

 - #52793 (Add test for NLL: unexpected "free region `` does not outlive" error )
 - #52799 (Use BitVector for global sets of AttrId)
 - #52809 (Add test for unexpected region for local data ReStatic)
 - #52834 ([NLL] Allow conflicting borrows of promoted length zero arrays)
 - #52835 (Fix Alias intra doc ICE)
 - #52854 (fix memrchr in miri)
 - #52899 (tests/ui: Add missing mips{64} ignores)
 - #52908 (Use SetLenOnDrop in Vec::truncate())
 - #52915 (Don't count MIR locals as borrowed after StorageDead when finding locals live across a yield terminator)
 - #52926 (rustc: Trim down the `rust_2018_idioms` lint group)
 - #52930 (rustc_resolve: record single-segment extern crate import resolutions.)
 - #52939 (Make io::Read::read_to_end consider io::Take::limit)
 - #52942 (Another SmallVec.extend optimization)
 - #52947 (1.27 actually added the `armv5te-unknown-linux-musleabi` target)
 - #52954 (async can begin expressions)

Failed merges:

r? @ghost

RELEASES.md

@@ -216,7 +216,7 @@ Language
 
 Compiler
 --------
-- [Added the `armv5te-unknown-linux-musl` target.][50423]
+- [Added the `armv5te-unknown-linux-musleabi` target.][50423]
 
 Libraries
 ---------

src/liballoc/vec.rs

@@ -690,14 +690,20 @@ impl<T> Vec<T> {
     /// [`drain`]: #method.drain
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn truncate(&mut self, len: usize) {
+        let current_len = self.len;
         unsafe {
+            let mut ptr = self.as_mut_ptr().offset(self.len as isize);
+            // Set the final length at the end, keeping in mind that
+            // dropping an element might panic. Works around a missed
+            // optimization, as seen in the following issue:
+            // https://github.com/rust-lang/rust/issues/51802
+            let mut local_len = SetLenOnDrop::new(&mut self.len);
+
             // drop any extra elements
-            while len < self.len {
-                // decrement len before the drop_in_place(), so a panic on Drop
-                // doesn't re-drop the just-failed value.
-                self.len -= 1;
-                let len = self.len;
-                ptr::drop_in_place(self.get_unchecked_mut(len));
+            for _ in len..current_len {
+                local_len.decrement_len(1);
+                ptr = ptr.offset(-1);
+                ptr::drop_in_place(ptr);
             }
         }
     }
@@ -1512,6 +1518,11 @@ impl<'a> SetLenOnDrop<'a> {
     fn increment_len(&mut self, increment: usize) {
         self.local_len += increment;
     }
+
+    #[inline]
+    fn decrement_len(&mut self, decrement: usize) {
+        self.local_len -= decrement;
+    }
 }
 
 impl<'a> Drop for SetLenOnDrop<'a> {

src/libcore/slice/memchr.rs

@@ -100,24 +100,30 @@ pub fn memrchr(x: u8, text: &[u8]) -> Option<usize> {
     // - the first remaining bytes, < 2 word size
     let len = text.len();
     let ptr = text.as_ptr();
-    let usize_bytes = mem::size_of::<usize>();
+    type Chunk = usize;
 
-    let mut offset = {
-        // We call this just to obtain the length of the suffix
-        let (_, _, suffix) = unsafe { text.align_to::<usize>() };
-        len - suffix.len()
+    let (min_aligned_offset, max_aligned_offset) = {
+        // We call this just to obtain the length of the prefix and suffix.
+        // In the middle we always process two chunks at once.
+        let (prefix, _, suffix) = unsafe { text.align_to::<(Chunk, Chunk)>() };
+        (prefix.len(), len - suffix.len())
     };
+
+    let mut offset = max_aligned_offset;
     if let Some(index) = text[offset..].iter().rposition(|elt| *elt == x) {
         return Some(offset + index);
     }
 
-    // search the body of the text
+    // search the body of the text, make sure we don't cross min_aligned_offset.
+    // offset is always aligned, so just testing `>` is sufficient and avoids possible
+    // overflow.
     let repeated_x = repeat_byte(x);
+    let chunk_bytes = mem::size_of::<Chunk>();
 
-    while offset >= 2 * usize_bytes {
+    while offset > min_aligned_offset {
         unsafe {
-            let u = *(ptr.offset(offset as isize - 2 * usize_bytes as isize) as *const usize);
-            let v = *(ptr.offset(offset as isize - usize_bytes as isize) as *const usize);
+            let u = *(ptr.offset(offset as isize - 2 * chunk_bytes as isize) as *const Chunk);
+            let v = *(ptr.offset(offset as isize - chunk_bytes as isize) as *const Chunk);
 
             // break if there is a matching byte
             let zu = contains_zero_byte(u ^ repeated_x);
@@ -126,7 +132,7 @@ pub fn memrchr(x: u8, text: &[u8]) -> Option<usize> {
                 break;
             }
         }
-        offset -= 2 * usize_bytes;
+        offset -= 2 * chunk_bytes;
     }
 
     // find the byte before the point the body loop stopped

src/librustc/mir/traversal.rs

@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use rustc_data_structures::bitvec::BitVector;
+use rustc_data_structures::bitvec::BitArray;
 
 use super::*;
 
@@ -32,7 +32,7 @@ use super::*;
 #[derive(Clone)]
 pub struct Preorder<'a, 'tcx: 'a> {
     mir: &'a Mir<'tcx>,
-    visited: BitVector<BasicBlock>,
+    visited: BitArray<BasicBlock>,
     worklist: Vec<BasicBlock>,
 }
 
@@ -42,7 +42,7 @@ impl<'a, 'tcx> Preorder<'a, 'tcx> {
 
         Preorder {
             mir,
-            visited: BitVector::new(mir.basic_blocks().len()),
+            visited: BitArray::new(mir.basic_blocks().len()),
             worklist,
         }
     }
@@ -104,15 +104,15 @@ impl<'a, 'tcx> ExactSizeIterator for Preorder<'a, 'tcx> {}
 /// A Postorder traversal of this graph is `D B C A` or `D C B A`
 pub struct Postorder<'a, 'tcx: 'a> {
     mir: &'a Mir<'tcx>,
-    visited: BitVector<BasicBlock>,
+    visited: BitArray<BasicBlock>,
     visit_stack: Vec<(BasicBlock, Successors<'a>)>
 }
 
 impl<'a, 'tcx> Postorder<'a, 'tcx> {
     pub fn new(mir: &'a Mir<'tcx>, root: BasicBlock) -> Postorder<'a, 'tcx> {
         let mut po = Postorder {
             mir,
-            visited: BitVector::new(mir.basic_blocks().len()),
+            visited: BitArray::new(mir.basic_blocks().len()),
             visit_stack: Vec::new()
         };
 

src/librustc/traits/select.rs

@@ -45,7 +45,7 @@ use middle::lang_items;
 use mir::interpret::{GlobalId};
 
 use rustc_data_structures::sync::Lock;
-use rustc_data_structures::bitvec::BitVector;
+use rustc_data_structures::bitvec::BitArray;
 use std::iter;
 use std::cmp;
 use std::fmt;
@@ -3056,7 +3056,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 } else {
                     return Err(Unimplemented);
                 };
-                let mut ty_params = BitVector::new(substs_a.types().count());
+                let mut ty_params = BitArray::new(substs_a.types().count());
                 let mut found = false;
                 for ty in field.walk() {
                     if let ty::TyParam(p) = ty.sty {

src/librustc_codegen_llvm/debuginfo/create_scope_map.rs

@@ -21,7 +21,7 @@ use libc::c_uint;
 
 use syntax_pos::Pos;
 
-use rustc_data_structures::bitvec::BitVector;
+use rustc_data_structures::bitvec::BitArray;
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
 
 use syntax_pos::BytePos;
@@ -64,7 +64,7 @@ pub fn create_mir_scopes(
     };
 
     // Find all the scopes with variables defined in them.
-    let mut has_variables = BitVector::new(mir.source_scopes.len());
+    let mut has_variables = BitArray::new(mir.source_scopes.len());
     for var in mir.vars_iter() {
         let decl = &mir.local_decls[var];
         has_variables.insert(decl.visibility_scope);
@@ -81,7 +81,7 @@ pub fn create_mir_scopes(
 
 fn make_mir_scope(cx: &CodegenCx<'ll, '_>,
                   mir: &Mir,
-                  has_variables: &BitVector<SourceScope>,
+                  has_variables: &BitArray<SourceScope>,
                   debug_context: &FunctionDebugContextData<'ll>,
                   scope: SourceScope,
                   scopes: &mut IndexVec<SourceScope, MirDebugScope<'ll>>) {

src/librustc_codegen_llvm/mir/analyze.rs

@@ -11,7 +11,7 @@
 //! An analysis to determine which locals require allocas and
 //! which do not.
 
-use rustc_data_structures::bitvec::BitVector;
+use rustc_data_structures::bitvec::BitArray;
 use rustc_data_structures::graph::dominators::Dominators;
 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
 use rustc::mir::{self, Location, TerminatorKind};
@@ -22,7 +22,7 @@ use rustc::ty::layout::LayoutOf;
 use type_of::LayoutLlvmExt;
 use super::FunctionCx;
 
-pub fn non_ssa_locals(fx: &FunctionCx<'a, 'll, 'tcx>) -> BitVector<mir::Local> {
+pub fn non_ssa_locals(fx: &FunctionCx<'a, 'll, 'tcx>) -> BitArray<mir::Local> {
     let mir = fx.mir;
     let mut analyzer = LocalAnalyzer::new(fx);
 
@@ -54,7 +54,7 @@ pub fn non_ssa_locals(fx: &FunctionCx<'a, 'll, 'tcx>) -> BitVector<mir::Local> {
 struct LocalAnalyzer<'mir, 'a: 'mir, 'll: 'a, 'tcx: 'll> {
     fx: &'mir FunctionCx<'a, 'll, 'tcx>,
     dominators: Dominators<mir::BasicBlock>,
-    non_ssa_locals: BitVector<mir::Local>,
+    non_ssa_locals: BitArray<mir::Local>,
     // The location of the first visited direct assignment to each
     // local, or an invalid location (out of bounds `block` index).
     first_assignment: IndexVec<mir::Local, Location>
@@ -67,7 +67,7 @@ impl LocalAnalyzer<'mir, 'a, 'll, 'tcx> {
         let mut analyzer = LocalAnalyzer {
             fx,
             dominators: fx.mir.dominators(),
-            non_ssa_locals: BitVector::new(fx.mir.local_decls.len()),
+            non_ssa_locals: BitArray::new(fx.mir.local_decls.len()),
             first_assignment: IndexVec::from_elem(invalid_location, &fx.mir.local_decls)
         };
 

src/librustc_codegen_llvm/mir/mod.rs

@@ -31,7 +31,7 @@ use syntax::symbol::keywords;
 
 use std::iter;
 
-use rustc_data_structures::bitvec::BitVector;
+use rustc_data_structures::bitvec::BitArray;
 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
 
 pub use self::constant::codegen_static_initializer;
@@ -323,7 +323,7 @@ pub fn codegen_mir(
     debuginfo::start_emitting_source_locations(&fx.debug_context);
 
     let rpo = traversal::reverse_postorder(&mir);
-    let mut visited = BitVector::new(mir.basic_blocks().len());
+    let mut visited = BitArray::new(mir.basic_blocks().len());
 
     // Codegen the body of each block using reverse postorder
     for (bb, _) in rpo {
@@ -417,7 +417,7 @@ fn arg_local_refs(
     bx: &Builder<'a, 'll, 'tcx>,
     fx: &FunctionCx<'a, 'll, 'tcx>,
     scopes: &IndexVec<mir::SourceScope, debuginfo::MirDebugScope<'ll>>,
-    memory_locals: &BitVector<mir::Local>,
+    memory_locals: &BitArray<mir::Local>,
 ) -> Vec<LocalRef<'ll, 'tcx>> {
     let mir = fx.mir;
     let tcx = bx.tcx();