Auto merge of rust-lang#73977 - Manishearth:rollup-2x4s7c6, r=Manishearth

Rollup of 8 pull requests

Successful merges:

 - rust-lang#73454 (Move contributing.md to rustc-dev-guide and point at getting started)
 - rust-lang#73724 (Use WASM's saturating casts if they are available)
 - rust-lang#73726 (resolve: disallow labelled breaks/continues through closures/async blocks)
 - rust-lang#73753 (Use 'tcx for references to AccessLevels wherever possible.)
 - rust-lang#73781 (Update psm version)
 - rust-lang#73952 (Add option for local docker testing.)
 - rust-lang#73957 (disable BTree min_max test in Miri for now)
 - rust-lang#73975 (Document rustc_ast::ast::Pat)

Failed merges:

r? @ghost

Author: bors

CONTRIBUTING.md

@@ -2347,9 +2347,9 @@ dependencies = [
 
 [[package]]
 name = "psm"
-version = "0.1.8"
+version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "659ecfea2142a458893bb7673134bad50b752fea932349c213d6a23874ce3aa7"
+checksum = "092d385624a084892d07374caa7b0994956692cf40650419a1f1a787a8d229cf"
 dependencies = [
  "cc",
 ]

Cargo.lock

@@ -7,6 +7,8 @@ standard library, and documentation.
 
 [Rust]: https://www.rust-lang.org
 
+**Note: this README is for _users_ rather than _contributors_.**
+
 ## Quick Start
 
 Read ["Installation"] from [The Book].
@@ -16,13 +18,15 @@ Read ["Installation"] from [The Book].
 
 ## Installing from Source
 
-_Note: If you wish to contribute to the compiler, you should read [this
-chapter][rustcguidebuild] of the rustc-dev-guide instead of this section._
+**Note: If you wish to _contribute_ to the compiler, you should read the
+[Getting Started][gettingstarted] of the rustc-dev-guide instead of this
+section.**
 
 The Rust build system uses a Python script called `x.py` to build the compiler,
 which manages the bootstrapping process. More information about it can be found 
 by running `./x.py --help` or reading the [rustc dev guide][rustcguidebuild].
 
+[gettingstarted]: https://rustc-dev-guide.rust-lang.org/getting-started.md
 [rustcguidebuild]: https://rustc-dev-guide.rust-lang.org/building/how-to-build-and-run.html
 
 ### Building on a Unix-like system
@@ -225,10 +229,6 @@ Snapshot binaries are currently built and tested on several platforms:
 You may find that other platforms work, but these are our officially
 supported build environments that are most likely to work.
 
-There is more advice about hacking on Rust in [CONTRIBUTING.md].
-
-[CONTRIBUTING.md]: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md
-
 ## Getting Help
 
 The Rust community congregates in a few places:
@@ -243,21 +243,8 @@ The Rust community congregates in a few places:
 
 ## Contributing
 
-To contribute to Rust, please see [CONTRIBUTING](CONTRIBUTING.md).
-
-Most real-time collaboration happens in a variety of channels on the
-[Rust Discord server][rust-discord], with channels dedicated for getting help,
-community, documentation, and all major contribution areas in the Rust ecosystem.
-A good place to ask for help would be the #help channel.
-
-The [rustc dev guide] might be a good place to start if you want to find out how
-various parts of the compiler work.
-
-Also, you may find the [rustdocs for the compiler itself][rustdocs] useful.
-
-[rust-discord]: https://discord.gg/rust-lang
-[rustc dev guide]: https://rustc-dev-guide.rust-lang.org/about-this-guide.html
-[rustdocs]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/
+If you are interested in contributing to the Rust project, please take a look
+at the [Getting Started][gettingstarted] guide in the [rustc-dev-guide].
 
 ## License
 

README.md

@@ -5,7 +5,27 @@ set -e
 export MSYS_NO_PATHCONV=1
 
 script=`cd $(dirname $0) && pwd`/`basename $0`
-image=$1
+
+image=""
+dev=0
+
+while [[ $# -gt 0 ]]
+do
+  case "$1" in
+    --dev)
+      dev=1
+      ;;
+    *)
+      if [ -n "$image" ]
+      then
+        echo "expected single argument for the image name"
+        exit 1
+      fi
+      image="$1"
+      ;;
+  esac
+  shift
+done
 
 docker_dir="`dirname $script`"
 ci_dir="`dirname $docker_dir`"
@@ -163,6 +183,15 @@ else
   args="$args --env LOCAL_USER_ID=`id -u`"
 fi
 
+if [ "$dev" = "1" ]
+then
+  # Interactive + TTY
+  args="$args -it"
+  command="/bin/bash"
+else
+  command="/checkout/src/ci/run.sh"
+fi
+
 docker \
   run \
   --workdir /checkout/obj \
@@ -183,7 +212,7 @@ docker \
   --init \
   --rm \
   rust-ci \
-  /checkout/src/ci/run.sh
+  $command
 
 if [ -f /.dockerenv ]; then
   rm -rf $objdir

src/ci/docker/run.sh

@@ -17,7 +17,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   wget \
   patch
 
-RUN curl -sL https://nodejs.org/dist/v9.2.0/node-v9.2.0-linux-x64.tar.xz | \
+RUN curl -sL https://nodejs.org/dist/v14.4.0/node-v14.4.0-linux-x64.tar.xz | \
   tar -xJ
 
 WORKDIR /build/
@@ -30,7 +30,7 @@ RUN sh /scripts/sccache.sh
 
 ENV RUST_CONFIGURE_ARGS \
   --musl-root-x86_64=/usr/local/x86_64-linux-musl \
-  --set build.nodejs=/node-v9.2.0-linux-x64/bin/node \
+  --set build.nodejs=/node-v14.4.0-linux-x64/bin/node \
   --set rust.lld
 
 # Some run-make tests have assertions about code size, and enabling debug

src/ci/docker/test-various/Dockerfile

@@ -310,6 +310,7 @@ fn test_iter_mixed() {
 }
 
 #[test]
+#[cfg_attr(miri, ignore)] // FIXME: fails in Miri <https://github.com/rust-lang/rust/issues/73915>
 fn test_iter_min_max() {
     let mut a = BTreeMap::new();
     assert_eq!(a.iter().min(), None);

src/liballoc/tests/btree/map.rs

@@ -511,6 +511,9 @@ pub struct Block {
     pub span: Span,
 }
 
+/// A match pattern.
+///
+/// Patterns appear in match statements and some other contexts, such as `let` and `if let`.
 #[derive(Clone, RustcEncodable, RustcDecodable, Debug)]
 pub struct Pat {
     pub id: NodeId,

src/librustc_ast/ast.rs

@@ -18,6 +18,7 @@ use rustc_data_structures::small_c_str::SmallCStr;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_span::sym;
 use rustc_target::abi::{self, Align, Size};
 use rustc_target::spec::{HasTargetSpec, Target};
 use std::borrow::Cow;
@@ -652,6 +653,56 @@ impl BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         unsafe { llvm::LLVMBuildSExt(self.llbuilder, val, dest_ty, UNNAMED) }
     }
 
+    fn fptoui_sat(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> Option<&'ll Value> {
+        // WebAssembly has saturating floating point to integer casts if the
+        // `nontrapping-fptoint` target feature is activated. We'll use those if
+        // they are available.
+        if self.sess().target.target.arch == "wasm32"
+            && self.sess().target_features.contains(&sym::nontrapping_fptoint)
+        {
+            let src_ty = self.cx.val_ty(val);
+            let float_width = self.cx.float_width(src_ty);
+            let int_width = self.cx.int_width(dest_ty);
+            let name = match (int_width, float_width) {
+                (32, 32) => Some("llvm.wasm.trunc.saturate.unsigned.i32.f32"),
+                (32, 64) => Some("llvm.wasm.trunc.saturate.unsigned.i32.f64"),
+                (64, 32) => Some("llvm.wasm.trunc.saturate.unsigned.i64.f32"),
+                (64, 64) => Some("llvm.wasm.trunc.saturate.unsigned.i64.f64"),
+                _ => None,
+            };
+            if let Some(name) = name {
+                let intrinsic = self.get_intrinsic(name);
+                return Some(self.call(intrinsic, &[val], None));
+            }
+        }
+        None
+    }
+
+    fn fptosi_sat(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> Option<&'ll Value> {
+        // WebAssembly has saturating floating point to integer casts if the
+        // `nontrapping-fptoint` target feature is activated. We'll use those if
+        // they are available.
+        if self.sess().target.target.arch == "wasm32"
+            && self.sess().target_features.contains(&sym::nontrapping_fptoint)
+        {
+            let src_ty = self.cx.val_ty(val);
+            let float_width = self.cx.float_width(src_ty);
+            let int_width = self.cx.int_width(dest_ty);
+            let name = match (int_width, float_width) {
+                (32, 32) => Some("llvm.wasm.trunc.saturate.signed.i32.f32"),
+                (32, 64) => Some("llvm.wasm.trunc.saturate.signed.i32.f64"),
+                (64, 32) => Some("llvm.wasm.trunc.saturate.signed.i64.f32"),
+                (64, 64) => Some("llvm.wasm.trunc.saturate.signed.i64.f64"),
+                _ => None,
+            };
+            if let Some(name) = name {
+                let intrinsic = self.get_intrinsic(name);
+                return Some(self.call(intrinsic, &[val], None));
+            }
+        }
+        None
+    }
+
     fn fptoui(&mut self, val: &'ll Value, dest_ty: &'ll Type) -> &'ll Value {
         unsafe { llvm::LLVMBuildFPToUI(self.llbuilder, val, dest_ty, UNNAMED) }
     }

src/librustc_codegen_llvm/builder.rs

@@ -497,6 +497,15 @@ impl CodegenCx<'b, 'tcx> {
             t_v8f64: t_f64, 8;
         }
 
+        ifn!("llvm.wasm.trunc.saturate.unsigned.i32.f32", fn(t_f32) -> t_i32);
+        ifn!("llvm.wasm.trunc.saturate.unsigned.i32.f64", fn(t_f64) -> t_i32);
+        ifn!("llvm.wasm.trunc.saturate.unsigned.i64.f32", fn(t_f32) -> t_i64);
+        ifn!("llvm.wasm.trunc.saturate.unsigned.i64.f64", fn(t_f64) -> t_i64);
+        ifn!("llvm.wasm.trunc.saturate.signed.i32.f32", fn(t_f32) -> t_i32);
+        ifn!("llvm.wasm.trunc.saturate.signed.i32.f64", fn(t_f64) -> t_i32);
+        ifn!("llvm.wasm.trunc.saturate.signed.i64.f32", fn(t_f32) -> t_i64);
+        ifn!("llvm.wasm.trunc.saturate.signed.i64.f64", fn(t_f64) -> t_i64);
+
         ifn!("llvm.trap", fn() -> void);
         ifn!("llvm.debugtrap", fn() -> void);
         ifn!("llvm.frameaddress", fn(t_i32) -> i8p);

src/librustc_codegen_llvm/context.rs

@@ -250,8 +250,11 @@ const RISCV_WHITELIST: &[(&str, Option<Symbol>)] = &[
     ("e", Some(sym::riscv_target_feature)),
 ];
 
-const WASM_WHITELIST: &[(&str, Option<Symbol>)] =
-    &[("simd128", Some(sym::wasm_target_feature)), ("atomics", Some(sym::wasm_target_feature))];
+const WASM_WHITELIST: &[(&str, Option<Symbol>)] = &[
+    ("simd128", Some(sym::wasm_target_feature)),
+    ("atomics", Some(sym::wasm_target_feature)),
+    ("nontrapping-fptoint", Some(sym::wasm_target_feature)),
+];
 
 /// When rustdoc is running, provide a list of all known features so that all their respective
 /// primitives may be documented.

src/librustc_codegen_llvm/llvm_util.rs

@@ -774,12 +774,17 @@ fn cast_float_to_int<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     float_ty: Bx::Type,
     int_ty: Bx::Type,
 ) -> Bx::Value {
-    let fptosui_result = if signed { bx.fptosi(x, int_ty) } else { bx.fptoui(x, int_ty) };
-
     if let Some(false) = bx.cx().sess().opts.debugging_opts.saturating_float_casts {
-        return fptosui_result;
+        return if signed { bx.fptosi(x, int_ty) } else { bx.fptoui(x, int_ty) };
+    }
+
+    let try_sat_result = if signed { bx.fptosi_sat(x, int_ty) } else { bx.fptoui_sat(x, int_ty) };
+    if let Some(try_sat_result) = try_sat_result {
+        return try_sat_result;
     }
 
+    let fptosui_result = if signed { bx.fptosi(x, int_ty) } else { bx.fptoui(x, int_ty) };
+
     let int_width = bx.cx().int_width(int_ty);
     let float_width = bx.cx().float_width(float_ty);
     // LLVM's fpto[su]i returns undef when the input x is infinite, NaN, or does not fit into the

src/librustc_codegen_ssa/mir/rvalue.rs

@@ -158,6 +158,8 @@ pub trait BuilderMethods<'a, 'tcx>:
 
     fn trunc(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
     fn sext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
+    fn fptoui_sat(&mut self, val: Self::Value, dest_ty: Self::Type) -> Option<Self::Value>;
+    fn fptosi_sat(&mut self, val: Self::Value, dest_ty: Self::Type) -> Option<Self::Value>;
     fn fptoui(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
     fn fptosi(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
     fn uitofp(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;

src/librustc_codegen_ssa/traits/builder.rs

@@ -448,6 +448,7 @@ E0763: include_str!("./error_codes/E0763.md"),
 E0764: include_str!("./error_codes/E0764.md"),
 E0765: include_str!("./error_codes/E0765.md"),
 E0766: include_str!("./error_codes/E0766.md"),
+E0767: include_str!("./error_codes/E0767.md"),
 ;
 //  E0006, // merged with E0005
 //  E0008, // cannot bind by-move into a pattern guard

src/librustc_error_codes/error_codes.rs

@@ -0,0 +1,20 @@
+An unreachable label was used.
+
+Erroneous code example:
+
+```compile_fail,E0767
+'a: loop {
+    || {
+        loop { break 'a } // error: use of unreachable label `'a`
+    };
+}
+```
+
+Ensure that the label is within scope. Labels are not reachable through
+functions, closures, async blocks or modules. Example:
+
+```
+'a: loop {
+    break 'a; // ok!
+}
+```

src/librustc_error_codes/error_codes/E0767.md

@@ -21,8 +21,8 @@ declare_lint_pass!(
     ArrayIntoIter => [ARRAY_INTO_ITER]
 );
 
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ArrayIntoIter {
-    fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'tcx>) {
+impl<'tcx> LateLintPass<'tcx> for ArrayIntoIter {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
         // We only care about method call expressions.
         if let hir::ExprKind::MethodCall(call, span, args, _) = &expr.kind {
             if call.ident.name != sym::into_iter {