Auto merge of #74375 - Manishearth:rollup-10vbpdh, r=Manishearth

Rollup of 14 pull requests

Successful merges:

 - #72973 (RISC-V GNU/Linux as host platform)
 - #73918 (Clean up E0715 explanation)
 - #73959 (Clean up E0716 explanation)
 - #74119 (Remove `Compiler::compile()`.)
 - #74196 (Add option to collapse automatically implementors)
 - #74218 (Add margin after doc search results)
 - #74276 (improve DiscriminantKind handling)
 - #74291 (Added docs for `From<c_int>` for `ExitStatus`)
 - #74294 (Update cross-compilation README)
 - #74337 (Handle case of incomplete local ty more gracefully)
 - #74344 (Remove string comparison and use diagnostic item instead)
 - #74347 (Initialize default providers only once)
 - #74353 (Edit docs for rustc_middle::dep_graph::dep_node)
 - #74374 (Add a 1.45 release note on lto vs. embed-bitcode)

Failed merges:

 - #74251 (Teach bootstrap about target files vs target triples)

r? @ghost

Author: bors

Diff for: .github/workflows/ci.yml

@@ -297,6 +297,9 @@ jobs:
           - name: dist-powerpc64le-linux
             os: ubuntu-latest-xl
             env: {}
+          - name: dist-riscv64-linux
+            os: ubuntu-latest-xl
+            env: {}
           - name: dist-s390x-linux
             os: ubuntu-latest-xl
             env: {}

Diff for: RELEASES.md

@@ -82,6 +82,9 @@ Stabilized APIs
 Cargo
 -----
 
+- [Cargo uses the `embed-bitcode` flag to optimize disk usage and build
+  time.][cargo/8066]
+
 Misc
 ----
 - [Rustdoc now supports strikethrough text in Markdown.][71928] E.g.
@@ -97,12 +100,18 @@ Compatibility Notes
 - [Rustdoc's CLI's extra error exit codes have been removed.][71900] These were
   previously undocumented and not intended for public use. Rustdoc still provides
   a non-zero exit code on errors.
+- [Rustc's `lto` flag is incompatible with the new `embed-bitcode=no`.][71848]
+  This may cause issues if LTO is enabled through `RUSTFLAGS` or `cargo rustc`
+  flags while cargo is adding `embed-bitcode` itself. The recommended way to
+  control LTO is with Cargo profiles, either in `Cargo.toml` or `.cargo/config`,
+  or by setting `CARGO_PROFILE_<name>_LTO` in the environment.
 
 Internals Only
 --------------
 - [Make clippy a git subtree instead of a git submodule][70655]
 - [Unify the undo log of all snapshot types][69464]
 
+[71848]: https://github.com/rust-lang/rust/issues/71848/
 [73420]: https://github.com/rust-lang/rust/issues/73420/
 [72324]: https://github.com/rust-lang/rust/pull/72324/
 [71843]: https://github.com/rust-lang/rust/pull/71843/
@@ -129,6 +138,7 @@ Internals Only
 [69813]: https://github.com/rust-lang/rust/pull/69813/
 [69464]: https://github.com/rust-lang/rust/pull/69464/
 [68717]: https://github.com/rust-lang/rust/pull/68717/
+[cargo/8066]: https://github.com/rust-lang/cargo/pull/8066
 [`Arc::as_ptr`]: https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#method.as_ptr
 [`BTreeMap::remove_entry`]: https://doc.rust-lang.org/stable/std/collections/struct.BTreeMap.html#method.remove_entry
 [`Rc::as_ptr`]: https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#method.as_ptr

Diff for: src/bootstrap/native.rs

@@ -112,6 +112,15 @@ impl Step for Llvm {
     /// Compile LLVM for `target`.
     fn run(self, builder: &Builder<'_>) -> PathBuf {
         let target = self.target;
+        let target_native = if self.target.starts_with("riscv") {
+            // RISC-V target triples in Rust is not named the same as C compiler target triples.
+            // This converts Rust RISC-V target triples to C compiler triples.
+            let idx = target.find('-').unwrap();
+
+            format!("riscv{}{}", &target[5..7], &target[idx..])
+        } else {
+            target.to_string()
+        };
 
         let Meta { stamp, build_llvm_config, out_dir, root } =
             match prebuilt_llvm_config(builder, target) {
@@ -165,8 +174,8 @@ impl Step for Llvm {
             .define("LLVM_ENABLE_BINDINGS", "OFF")
             .define("LLVM_ENABLE_Z3_SOLVER", "OFF")
             .define("LLVM_PARALLEL_COMPILE_JOBS", builder.jobs().to_string())
-            .define("LLVM_TARGET_ARCH", target.split('-').next().unwrap())
-            .define("LLVM_DEFAULT_TARGET_TRIPLE", target);
+            .define("LLVM_TARGET_ARCH", target_native.split('-').next().unwrap())
+            .define("LLVM_DEFAULT_TARGET_TRIPLE", target_native);
 
         if !target.contains("netbsd") {
             cfg.define("LLVM_ENABLE_ZLIB", "ON");
@@ -213,6 +222,17 @@ impl Step for Llvm {
             }
         }
 
+        if target.starts_with("riscv") {
+            // In RISC-V, using C++ atomics require linking to `libatomic` but the LLVM build
+            // system check cannot detect this. Therefore it is set manually here.
+            if !builder.config.llvm_tools_enabled {
+                cfg.define("CMAKE_EXE_LINKER_FLAGS", "-latomic");
+            } else {
+                cfg.define("CMAKE_EXE_LINKER_FLAGS", "-latomic -static-libstdc++");
+            }
+            cfg.define("CMAKE_SHARED_LINKER_FLAGS", "-latomic");
+        }
+
         if target.contains("msvc") {
             cfg.define("LLVM_USE_CRT_DEBUG", "MT");
             cfg.define("LLVM_USE_CRT_RELEASE", "MT");

Diff for: src/ci/azure-pipelines/auto.yml

@@ -53,6 +53,7 @@ jobs:
       dist-powerpc-linux: {}
       dist-powerpc64-linux: {}
       dist-powerpc64le-linux: {}
+      dist-riscv64-linux: {}
       dist-s390x-linux: {}
       dist-x86_64-freebsd: {}
       dist-x86_64-illumos: {}

Diff for: src/ci/docker/README.md

@@ -16,6 +16,11 @@ for example:
 
 Images will output artifacts in an `obj` dir at the root of a repository.
 
+To match conditions in rusts CI, also set the environment variable `DEPLOY=1`, e.g.:
+```
+DEPLOY=1 ./src/ci/docker/run.sh x86_64-gnu
+```
+
 **NOTE**: Re-using the same `obj` dir with different docker images with
 the same target triple (e.g. `dist-x86_64-linux` and `dist-various-1`)
 may result in strange linker errors, due shared library versions differing between platforms.
@@ -85,42 +90,60 @@ how to generate them, and how the existing ones were generated.
 
 ### Generating a `.config` file
 
+**NOTE:** Existing Dockerfiles can also be a good guide for the process and order
+of script execution.
+
 If you have a `linux-cross` image lying around you can use that and skip the
 next two steps.
 
-- First we spin up a container and copy `build_toolchain_root.sh` into it. All
+- First we spin up a container and copy all scripts into it. All
   these steps are outside the container:
 
 ```
-# Note: We use ubuntu:15.10 because that's the "base" of linux-cross Docker
-# image
-$ docker run -it ubuntu:15.10 bash
+# Note: We use ubuntu:16.04 because that's the "base" of linux-cross Docker
+# image, or simply run ./src/ci/docker/run.sh once, which will download the correct
+# one and you can check it out with `docker images`
+$ docker run -it ubuntu:16.04 bash
+# in another terminal:
 $ docker ps
 CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
-cfbec05ed730        ubuntu:15.10        "bash"              16 seconds ago      Up 15 seconds                           drunk_murdock
-$ docker cp build_toolchain_root.sh drunk_murdock:/
+cfbec05ed730        ubuntu:16.04        "bash"              16 seconds ago      Up 15 seconds                           drunk_murdock
+$ docker cp src/ci/docker/scripts drunk_murdock:/tmp/
 ```
 
 - Then inside the container we build crosstool-ng by simply calling the bash
   script we copied in the previous step:
 
 ```
-$ bash build_toolchain_root.sh
+$ cd /tmp/scripts
+# Download packages necessary for building
+$ bash ./cross-apt-packages.sh
+# Download and build crosstool-ng
+$ bash ./crosstool-ng.sh
+```
+
+- In case you want to adjust or start from an existing config, copy that
+  to the container. `crosstool-ng` will automatically load `./.config` if
+  present. Otherwise one can use the TUI to load any config-file.
+
+```
+$ docker cp arm-linux-gnueabi.config drunk_murdock:/tmp/.config
 ```
 
 - Now, inside the container run the following command to configure the
   toolchain. To get a clue of which options need to be changed check the next
   section and come back.
 
 ```
+$ cd /tmp/
 $ ct-ng menuconfig
 ```
 
 - Finally, we retrieve the `.config` file from the container and give it a
   meaningful name. This is done outside the container.
 
 ```
-$ docker drunk_murdock:/.config arm-linux-gnueabi.config
+$ docker cp drunk_murdock:/tmp/.config arm-linux-gnueabi.config
 ```
 
 - Now you can shutdown the container or repeat the two last steps to generate a

Diff for: src/ci/docker/host-x86_64/dist-riscv64-linux/Dockerfile

@@ -0,0 +1,31 @@
+FROM ubuntu:18.04
+
+COPY scripts/cross-apt-packages.sh /scripts/
+RUN sh /scripts/cross-apt-packages.sh
+
+COPY host-x86_64/dist-riscv64-linux/crosstool-ng.sh /scripts/
+RUN sh /scripts/crosstool-ng.sh
+
+COPY scripts/rustbuild-setup.sh /scripts/
+RUN sh /scripts/rustbuild-setup.sh
+USER rustbuild
+WORKDIR /tmp
+
+COPY host-x86_64/dist-riscv64-linux/build-toolchains.sh host-x86_64/dist-riscv64-linux/riscv64-unknown-linux-gnu.config /tmp/
+RUN ./build-toolchains.sh
+
+USER root
+
+COPY scripts/sccache.sh /scripts/
+RUN sh /scripts/sccache.sh
+
+ENV PATH=$PATH:/x-tools/riscv64-unknown-linux-gnu/bin
+
+ENV CC_riscv64gc_unknown_linux_gnu=riscv64-unknown-linux-gnu-gcc \
+    AR_riscv64gc_unknown_linux_gnu=riscv64-unknown-linux-gnu-ar \
+    CXX_riscv64gc_unknown_linux_gnu=riscv64-unknown-linux-gnu-g++
+
+ENV HOSTS=riscv64gc-unknown-linux-gnu
+
+ENV RUST_CONFIGURE_ARGS --enable-extended --disable-docs
+ENV SCRIPT python3 ../x.py dist --target $HOSTS --host $HOSTS

Diff for: src/ci/docker/host-x86_64/dist-various-1/build-riscv-toolchain.sh renamed to src/ci/docker/host-x86_64/dist-riscv64-linux/build-toolchains.sh

@@ -19,9 +19,9 @@ exit 1
   set -x
 }
 
-mkdir -p /tmp/build-riscv
-cp riscv64-unknown-linux-gnu.config /tmp/build-riscv/.config
-cd /tmp/build-riscv
+mkdir build
+cd build
+cp ../riscv64-unknown-linux-gnu.config .config
 hide_output ct-ng build
 cd ..
-rm -rf build-riscv
+rm -rf build

Diff for: src/ci/docker/host-x86_64/dist-various-1/crosstool-ng.sh renamed to src/ci/docker/host-x86_64/dist-riscv64-linux/crosstool-ng.sh

@@ -1,4 +1,3 @@
-#!/bin/bash
 set -ex
 
 # Mirrored from https://github.com/crosstool-ng/crosstool-ng/archive/crosstool-ng-1.24.0.tar.gz

Diff for: src/ci/docker/host-x86_64/dist-various-1/riscv64-unknown-linux-gnu.config renamed to src/ci/docker/host-x86_64/dist-riscv64-linux/riscv64-unknown-linux-gnu.config

@@ -17,8 +17,6 @@ CT_CONFIGURE_has_gnu_m4_1_4_12_or_newer=y
 CT_CONFIGURE_has_python_3_4_or_newer=y
 CT_CONFIGURE_has_bison_2_7_or_newer=y
 CT_CONFIGURE_has_python=y
-CT_CONFIGURE_has_dtc=y
-CT_CONFIGURE_has_svn=y
 CT_CONFIGURE_has_git=y
 CT_CONFIGURE_has_md5sum=y
 CT_CONFIGURE_has_sha1sum=y

Diff for: src/ci/docker/host-x86_64/dist-various-1/Dockerfile

@@ -47,18 +47,6 @@ RUN add-apt-repository ppa:team-gcc-arm-embedded/ppa && \
     apt-get update && \
     apt-get install -y --no-install-recommends gcc-arm-embedded
 
-COPY scripts/rustbuild-setup.sh host-x86_64/dist-various-1/build-riscv-toolchain.sh host-x86_64/dist-various-1/riscv64-unknown-linux-gnu.config host-x86_64/dist-various-1/crosstool-ng.sh /build/
-RUN ./crosstool-ng.sh
-
-# Crosstool-ng will refuse to build as root
-RUN sh ./rustbuild-setup.sh
-USER rustbuild
-
-RUN ./build-riscv-toolchain.sh
-
-USER root
-ENV PATH=/x-tools/riscv64-unknown-linux-gnu/bin:$PATH
-
 COPY host-x86_64/dist-various-1/build-rumprun.sh /build
 RUN ./build-rumprun.sh
 
@@ -158,7 +146,6 @@ ENV TARGETS=$TARGETS,riscv32imc-unknown-none-elf
 ENV TARGETS=$TARGETS,riscv32imac-unknown-none-elf
 ENV TARGETS=$TARGETS,riscv64imac-unknown-none-elf
 ENV TARGETS=$TARGETS,riscv64gc-unknown-none-elf
-ENV TARGETS=$TARGETS,riscv64gc-unknown-linux-gnu
 ENV TARGETS=$TARGETS,armebv7r-none-eabi
 ENV TARGETS=$TARGETS,armebv7r-none-eabihf
 ENV TARGETS=$TARGETS,armv7r-none-eabi
@@ -186,9 +173,6 @@ ENV CC_mipsel_unknown_linux_musl=mipsel-openwrt-linux-gcc \
     CFLAGS_aarch64_unknown_none_softfloat=-mstrict-align -march=armv8-a+nofp+nosimd \
     CC_aarch64_unknown_none=aarch64-none-elf-gcc \
     CFLAGS_aarch64_unknown_none=-mstrict-align -march=armv8-a+fp+simd \
-    CC_riscv64gc_unknown_linux_gnu=riscv64-unknown-linux-gnu-gcc \
-    AR_riscv64gc_unknown_linux_gnu=riscv64-unknown-linux-gnu-ar \
-    CXX_riscv64gc_unknown_linux_gnu=riscv64-unknown-linux-gnu-g++ \
     CC_riscv32i_unknown_none_elf=false \
     CC_riscv32imc_unknown_none_elf=false \
     CC_riscv32imac_unknown_none_elf=false \

Diff for: src/ci/github-actions/ci.yml

@@ -341,6 +341,9 @@ jobs:
           - name: dist-powerpc64le-linux
             <<: *job-linux-xl
 
+          - name: dist-riscv64-linux
+            <<: *job-linux-xl
+
           - name: dist-s390x-linux
             <<: *job-linux-xl
 

Diff for: src/libcore/marker.rs

@@ -693,6 +693,7 @@ mod impls {
 pub trait DiscriminantKind {
     /// The type of the discriminant, which must satisfy the trait
     /// bounds required by `mem::Discriminant`.
+    #[cfg_attr(not(bootstrap), lang = "discriminant_type")]
     type Discriminant: Clone + Copy + Debug + Eq + PartialEq + Hash + Send + Sync + Unpin;
 }
 

Diff for: src/libcore/option.rs

@@ -1681,6 +1681,7 @@ impl<A, V: FromIterator<A>> FromIterator<Option<A>> for Option<V> {
 /// to allow `x?` (where `x` is an `Option<T>`) to be converted into your error type, you can
 /// implement `impl From<NoneError>` for `YourErrorType`. In that case, `x?` within a function that
 /// returns `Result<_, YourErrorType>` will translate a `None` value into an `Err` result.
+#[rustc_diagnostic_item = "none_error"]
 #[unstable(feature = "try_trait", issue = "42327")]
 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
 pub struct NoneError;

Diff for: src/librustc_error_codes/error_codes/E0715.md

@@ -15,8 +15,7 @@ struct OverrideConst;
 impl Marker for OverrideConst { // error!
     const N: usize = 1;
 }
-
-fn main() {}
+# fn main() {}
 ```
 
 Because marker traits are allowed to have multiple implementations for the same