Auto merge of #88321 - glaubitz:m68k-linux, r=wesleywiser

Add initial support for m68k

This patch series adds initial support for m68k making use of the new M68k
backend introduced with LLVM-13. Additional changes will be needed to be
able to actually use the backend for this target.

src/bootstrap/bootstrap.py

@@ -277,6 +277,7 @@ def default_build_triple(verbose):
         'i486': 'i686',
         'i686': 'i686',
         'i786': 'i686',
+        'm68k': 'm68k',
         'powerpc': 'powerpc',
         'powerpc64': 'powerpc64',
         'powerpc64le': 'powerpc64le',

src/bootstrap/native.rs

@@ -165,7 +165,7 @@ impl Step for Llvm {
 
         let llvm_exp_targets = match builder.config.llvm_experimental_targets {
             Some(ref s) => s,
-            None => "AVR",
+            None => "AVR;M68k",
         };
 
         let assertions = if builder.config.llvm_assertions { "ON" } else { "OFF" };

src/ci/docker/host-x86_64/disabled/dist-m68k-linux/Dockerfile

@@ -0,0 +1,26 @@
+FROM ubuntu:20.04
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+  g++ \
+  make \
+  file \
+  curl \
+  ca-certificates \
+  python2.7 \
+  git \
+  cmake \
+  sudo \
+  gdb \
+  xz-utils \
+  g++-m68k-linux-gnu \
+  libssl-dev \
+  pkg-config
+
+
+COPY scripts/sccache.sh /scripts/
+RUN sh /scripts/sccache.sh
+
+ENV HOSTS=m68k-unknown-linux-gnu
+
+ENV RUST_CONFIGURE_ARGS --host=$HOSTS --enable-extended
+ENV SCRIPT python3 ../x.py dist --host $HOSTS --target $HOSTS

src/doc/rustc/src/platform-support.md

@@ -238,6 +238,7 @@ target | std | host | notes
 `i686-uwp-windows-gnu` | ? |  |
 `i686-uwp-windows-msvc` | ? |  |
 `i686-wrs-vxworks` | ? |  |
+`m68k-unknown-linux-gnu` | ? |  | Motorola 680x0 Linux
 `mips-unknown-linux-uclibc` | ✓ |  | MIPS Linux with uClibc
 `mipsel-sony-psp` | * |  | MIPS (LE) Sony PlayStation Portable (PSP)
 `mipsel-unknown-linux-uclibc` | ✓ |  | MIPS (LE) Linux with uClibc

src/doc/rustc/src/platform-support/m68k-unknown-linux-gnu.md

@@ -0,0 +1,97 @@
+# m68k-unknown-linux-gnu
+
+**Tier: 3**
+
+Motorola 680x0 Linux
+
+## Designated Developers
+
+* [@glaubitz](https://github.com/glaubitz)
+* [@ricky26](https://github.com/ricky26)
+
+## Requirements
+
+This target requires a Linux/m68k build environment for cross-compilation which
+is available on Debian and Debian-based systems, openSUSE and other distributions.
+
+On Debian, it should be sufficient to install a g++ cross-compiler for the m68k
+architecture which will automatically pull in additional dependencies such as
+the glibc cross development package:
+
+```text
+# apt install g++-m68k-linux-gnu
+```
+
+Binaries can be run using QEMU user emulation. On Debian-based systems, it should be
+sufficient to install the package `qemu-user-static` to be able to run simple static
+binaries:
+
+```text
+# apt install qemu-user-static
+```
+
+To run more complex programs, it will be necessary to set up a Debian/m68k chroot with
+the help of the command `debootstrap`:
+
+```text
+# apt install debootstrap debian-ports-archive-keyring
+# debootstrap --keyring=/usr/share/keyrings/debian-ports-archive-keyring.gpg --arch=m68k unstable debian-68k http://ftp.ports.debian.org/debian-ports
+```
+
+This chroot can then seamlessly entered using the normal `chroot` command thanks to
+QEMU user emulation:
+
+```text
+# chroot /path/to/debian-68k
+```
+
+To get started with native builds, which are currently untested, a native Debian/m68k
+system can be installed either on real hardware such as 68k-based Commodore Amiga or
+Atari systems or emulated environments such as QEMU version 4.2 or newer or ARAnyM.
+
+ISO images for installation are provided by the Debian Ports team and can be obtained
+from the Debian CD image server available at:
+
+[https://cdimage.debian.org/cdimage/ports/current](https://cdimage.debian.org/cdimage/ports/current/)
+
+Documentation for Debian/m68k is available on the Debian Wiki at:
+
+[https://wiki.debian.org/M68k](https://wiki.debian.org/M68k)
+
+Support is available either through the `debian-68k` mailing list:
+
+[https://lists.debian.org/debian-68k/](https://lists.debian.org/debian-68k/)
+
+or the `#debian-68k` IRC channel on OFTC network.
+
+## Building
+
+The codegen for this target should be built by default. However, core and std
+are currently missing but are being worked on and should become available in
+the near future.
+
+## Cross-compilation
+
+This target can be cross-compiled from a standard Debian or Debian-based, openSUSE or any
+other distribution which has a basic m68k cross-toolchain available.
+
+## Testing
+
+Currently there is no support to run the rustc test suite for this target.
+
+## Building Rust programs
+
+Rust programs can be built for that target:
+
+```text
+rustc --target m68k-unknown-linux-gnu your-code.rs
+```
+
+Very simple progams can be run using the `qemu-m68k-static` program:
+
+```text
+$ qemu-m68k-static your-code
+```
+
+For more complex applications, a chroot or native (emulated) Debian/m68k system are required
+for testing.

src/librustdoc/clean/cfg.rs

@@ -491,6 +491,7 @@ impl<'a> fmt::Display for Display<'a> {
                         "aarch64" => "AArch64",
                         "arm" => "ARM",
                         "asmjs" => "JavaScript",
+                        "m68k" => "M68k",
                         "mips" => "MIPS",
                         "mips64" => "MIPS-64",
                         "msp430" => "MSP430",

src/tools/build-manifest/src/main.rs

@@ -99,6 +99,7 @@ static TARGETS: &[&str] = &[
     "i686-unknown-freebsd",
     "i686-unknown-linux-gnu",
     "i686-unknown-linux-musl",
+    "m68k-unknown-linux-gnu",
     "mips-unknown-linux-gnu",
     "mips-unknown-linux-musl",
     "mips64-unknown-linux-gnuabi64",

src/tools/compiletest/src/util.rs

@@ -54,6 +54,7 @@ const ARCH_TABLE: &[(&str, &str)] = &[
     ("i386", "x86"),
     ("i586", "x86"),
     ("i686", "x86"),
+    ("m68k", "m68k"),
     ("mips", "mips"),
     ("mips64", "mips64"),
     ("mips64el", "mips64"),