Create a generic AVR target: avr-unknown-unknown

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1920,10 +1920,20 @@ fn add_post_link_objects(
 
 /// Add arbitrary "pre-link" args defined by the target spec or from command line.
 /// FIXME: Determine where exactly these args need to be inserted.
-fn add_pre_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor) {
+fn add_pre_link_args(
+ cmd: &mut dyn Linker,
+ sess: &Session,
+ flavor: LinkerFlavor,
+ codegen_results: &CodegenResults,
+) {
  if let Some(args) = sess.target.pre_link_args.get(&flavor) {
  cmd.verbatim_args(args.iter().map(Deref::deref));
  }
+
+ if sess.target.arch == "avr" {
+ cmd.verbatim_arg(format!("-mmcu={}", codegen_results.crate_info.target_cpu));
+ }
+
  cmd.verbatim_args(&sess.opts.unstable_opts.pre_link_args);
 }
 
@@ -2215,7 +2225,7 @@ fn linker_with_args(
  // FIXME: In practice built-in target specs use this for arbitrary order-independent options,
  // introduce a target spec option for order-independent linker options and migrate built-in
  // specs to it.
- add_pre_link_args(cmd, sess, flavor);
+ add_pre_link_args(cmd, sess, flavor, codegen_results);
 
  // ------------ Object code and libraries, order-dependent ------------
 

compiler/rustc_target/src/spec/base/avr_gnu.rs → compiler/rustc_target/src/spec/base/avr.rs

@@ -1,44 +1,5 @@
 use object::elf;
 
-use crate::spec::{Cc, LinkerFlavor, Lld, RelocModel, Target, TargetOptions};
-
-/// A base target for AVR devices using the GNU toolchain.
-///
-/// Requires GNU avr-gcc and avr-binutils on the host system.
-/// FIXME: Remove the second parameter when const string concatenation is possible.
-pub(crate) fn target(target_cpu: &'static str, mmcu: &'static str) -> Target {
- Target {
- arch: "avr".into(),
- metadata: crate::spec::TargetMetadata {
- description: None,
- tier: None,
- host_tools: None,
- std: None,
- },
- data_layout: "e-P1-p:16:8-i8:8-i16:8-i32:8-i64:8-f32:8-f64:8-n8-a:8".into(),
- llvm_target: "avr-unknown-unknown".into(),
- pointer_width: 16,
- options: TargetOptions {
- env: "gnu".into(),
-
- c_int_width: "16".into(),
- cpu: target_cpu.into(),
- exe_suffix: ".elf".into(),
-
- linker: Some("avr-gcc".into()),
- eh_frame_header: false,
- pre_link_args: TargetOptions::link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &[mmcu]),
- late_link_args: TargetOptions::link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &[
- "-lgcc",
- ]),
- max_atomic_width: Some(16),
- atomic_cas: false,
- relocation_model: RelocModel::Static,
- ..TargetOptions::default()
- },
- }
-}
-
 /// Resolve the value of the EF_AVR_ARCH field for AVR ELF files, given the
 /// name of the target CPU / MCU.
 ///

compiler/rustc_target/src/spec/base/mod.rs

@@ -1,7 +1,7 @@
 pub(crate) mod aix;
 pub(crate) mod android;
 pub(crate) mod apple;
-pub(crate) mod avr_gnu;
+pub(crate) mod avr;
 pub(crate) mod bpf;
 pub(crate) mod dragonfly;
 pub(crate) mod freebsd;

compiler/rustc_target/src/spec/mod.rs

@@ -63,7 +63,7 @@ pub use base::apple::{
  deployment_target_for_target as current_apple_deployment_target,
  platform as current_apple_platform,
 };
-pub use base::avr_gnu::ef_avr_arch;
+pub use base::avr::ef_avr_arch;
 
 /// Linker is called through a C/C++ compiler.
 #[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
@@ -1734,7 +1734,7 @@ supported_targets! {
  ("riscv64gc-unknown-fuchsia", riscv64gc_unknown_fuchsia),
  ("x86_64-unknown-fuchsia", x86_64_unknown_fuchsia),
 
- ("avr-unknown-gnu-atmega328", avr_unknown_gnu_atmega328),
+ ("avr-unknown-unknown", avr_unknown_unknown),
 
  ("x86_64-unknown-l4re-uclibc", x86_64_unknown_l4re_uclibc),
 

compiler/rustc_target/src/spec/targets/avr_unknown_unknown.rs

@@ -0,0 +1,30 @@
+use crate::spec::{Cc, LinkerFlavor, Lld, RelocModel, Target, TargetOptions};
+
+pub(crate) fn target() -> Target {
+ Target {
+ arch: "avr".into(),
+ metadata: crate::spec::TargetMetadata {
+ description: None,
+ tier: None,
+ host_tools: None,
+ std: None,
+ },
+ data_layout: "e-P1-p:16:8-i8:8-i16:8-i32:8-i64:8-f32:8-f64:8-n8-a:8".into(),
+ llvm_target: "avr-unknown-unknown".into(),
+ pointer_width: 16,
+ options: TargetOptions {
+ c_int_width: "16".into(),
+ exe_suffix: ".elf".into(),
+ linker: Some("avr-gcc".into()),
+ eh_frame_header: false,
+ pre_link_args: TargetOptions::link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &[]),
+ late_link_args: TargetOptions::link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &[
+ "-lgcc",
+ ]),
+ max_atomic_width: Some(16),
+ atomic_cas: false,
+ relocation_model: RelocModel::Static,
+ ..TargetOptions::default()
+ },
+ }
+}

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

@@ -293,7 +293,7 @@ target | std | host | notes
 [`armv7k-apple-watchos`](platform-support/apple-watchos.md) | ✓ | | Armv7-A Apple WatchOS
 [`armv7s-apple-ios`](platform-support/apple-ios.md) | ✓ | | Armv7-A Apple-A6 Apple iOS
 [`armv8r-none-eabihf`](platform-support/armv8r-none-eabihf.md) | * | | Bare Armv8-R, hardfloat
-`avr-unknown-gnu-atmega328` | * | | AVR. Requires `-Z build-std=core`
+`avr-unknown-unknown` | * | | AVR
 `bpfeb-unknown-none` | * | | BPF (big endian)
 `bpfel-unknown-none` | * | | BPF (little endian)
 `csky-unknown-linux-gnuabiv2` | ✓ | | C-SKY abiv2 Linux (little endian)

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

@@ -0,0 +1,75 @@
+# `avr-unknown-unknown`
+
+Series of microcontrollers from Atmel: ATmega8, ATmega328p etc.
+
+**Tier: 3**
+
+## Target maintainers
+
+-[Patryk Wychowaniec](https://github.com/Patryk27) <[email protected]>
+
+## Requirements
+
+This target is only cross-compiled - x86_64 / aarch64 x Lixux / MacOS hosts are
+confirmed to work, but in principle any machine able to run rustc and avr-gcc
+should be good.
+
+Compiling for this target requires `avr-gcc`, because a couple of intrinsics
+(like 32-bit multiplication) rely on [`libgcc`](https://github.com/gcc-mirror/gcc/blob/3269a722b7a03613e9c4e2862bc5088c4a17cc11/libgcc/config/avr/lib1funcs.S)
+and can't be provided through `compiler-builtins` yet; this is a limitation that
+we hope to lift in the future, see https://github.com/rust-lang/compiler-builtins/issues/711.
+
+## Building the target
+
+Rust comes with AVR support enabled, you don't have to rebuild the compiler
+itself.
+
+## Building Rust programs
+
+Install `avr-gcc`:
+
+```console
+# Ubuntu:
+$ sudo apt-get install gcc-avr
+
+# Mac:
+$ brew tap osx-cross/avr && brew install avr-gcc
+
+# NixOS (takes a couple of minutes, since Hydra doesn't build it):
+$ nix shell nixpkgs#pkgsCross.avr.buildPackages.gcc11
+```
+
+... setup `.cargo/config` for your project:
+
+```toml
+[build]
+target = "avr-unknown-unknown"
+rustflags = ["-C", "target-cpu=atmega328p"]
+
+[unstable]
+build-std = ["core"]
+```
+
+... and then simply run:
+
+```console
+$ cargo build --release
+```
+
+The final binary will be placed into
+`./target/avr-unknown-unknown/release/your-project.elf`.
+
+Note that since AVRs have rather small amounts of registers, ROM and RAM, it's
+recommended to always use `--release` to avoid running out of space.
+
+## Testing
+
+You can use [`simavr`](https://github.com/buserror/simavr) to emulate the
+resulting firmware on your machine:
+
+```
+simavr -m atmega328p ./target/avr-unknown-unknown/release/your-project.elf
+```
+
+Alternatively, if you want to write a couple of actual `#[test]`s, you can use
+[`avr-tester`](https://github.com/Patryk27/avr-tester).

src/tools/compiletest/src/header/tests.rs

@@ -380,7 +380,10 @@ fn profiler_runtime() {
 #[test]
 fn asm_support() {
  let asms = [
+ #[cfg(bootstrap)]
  ("avr-unknown-gnu-atmega328", false),
+ #[cfg(not(bootstrap))]
+ ("avr-unknown-unknown", false),
  ("i686-unknown-netbsd", true),
  ("riscv32gc-unknown-linux-gnu", true),
  ("riscv64imac-unknown-none-elf", true),

tests/assembly/asm/avr-modifiers.rs

@@ -1,5 +1,5 @@
 //@ assembly-output: emit-asm
-//@ compile-flags: --target avr-unknown-gnu-atmega328
+//@ compile-flags: --target avr-unknown-unknown -C target-cpu=atmega328p
 //@ needs-llvm-components: avr
 
 #![feature(no_core, lang_items, rustc_attrs, asm_experimental_arch)]

tests/assembly/asm/avr-types.rs

@@ -1,5 +1,5 @@
 //@ assembly-output: emit-asm
-//@ compile-flags: --target avr-unknown-gnu-atmega328
+//@ compile-flags: --target avr-unknown-unknown -C target-cpu=atmega328p
 //@ needs-llvm-components: avr
 
 #![feature(no_core, lang_items, rustc_attrs, asm_experimental_arch)]

tests/assembly/targets/targets-pe.rs

@@ -15,9 +15,9 @@
 //@ revisions: arm64ec_pc_windows_msvc
 //@ [arm64ec_pc_windows_msvc] compile-flags: --target arm64ec-pc-windows-msvc
 //@ [arm64ec_pc_windows_msvc] needs-llvm-components: aarch64
-//@ revisions: avr_unknown_gnu_atmega328
-//@ [avr_unknown_gnu_atmega328] compile-flags: --target avr-unknown-gnu-atmega328
-//@ [avr_unknown_gnu_atmega328] needs-llvm-components: avr
+//@ revisions: avr_unknown_unknown
+//@ [avr_unknown_unknown] compile-flags: --target avr-unknown-unknown -C target-cpu=atmega328p
+//@ [avr_unknown_unknown] needs-llvm-components: avr
 //@ revisions: bpfeb_unknown_none
 //@ [bpfeb_unknown_none] compile-flags: --target bpfeb-unknown-none
 //@ [bpfeb_unknown_none] needs-llvm-components: bpf

tests/codegen/avr/avr-func-addrspace.rs

@@ -1,4 +1,4 @@
-//@ compile-flags: -O --target=avr-unknown-gnu-atmega328 --crate-type=rlib -C panic=abort
+//@ compile-flags: -O --target=avr-unknown-unknown -C target-cpu=atmega328p --crate-type=rlib -C panic=abort
 //@ needs-llvm-components: avr
 
 // This test validates that function pointers can be stored in global variables

tests/ui/feature-gates/feature-gate-abi-avr-interrupt.rs

@@ -1,5 +1,5 @@
 //@ needs-llvm-components: avr
-//@ compile-flags: --target=avr-unknown-gnu-atmega328 --crate-type=rlib
+//@ compile-flags: --target=avr-unknown-unknown -C target-cpu=atmega328p --crate-type=rlib
 #![no_core]
 #![feature(no_core, lang_items)]
 #[lang="sized"]

tests/ui/repr/16-bit-repr-c-enum.rs

@@ -2,7 +2,7 @@
 //@ revisions: avr msp430
 //
 //@ [avr] needs-llvm-components: avr
-//@ [avr] compile-flags: --target=avr-unknown-gnu-atmega328 --crate-type=rlib
+//@ [avr] compile-flags: --target=avr-unknown-unknown -C target-cpu=atmega328p --crate-type=rlib
 //@ [msp430] needs-llvm-components: msp430
 //@ [msp430] compile-flags: --target=msp430-none-elf --crate-type=rlib
 #![feature(no_core, lang_items, intrinsics, staged_api, rustc_attrs)]