Add a sparc-unknown-none-elf target.

compiler/rustc_target/src/spec/mod.rs

@@ -1433,6 +1433,8 @@ supported_targets! {
     ("riscv64gc-unknown-linux-gnu", riscv64gc_unknown_linux_gnu),
     ("riscv64gc-unknown-linux-musl", riscv64gc_unknown_linux_musl),
 
+    ("sparc-unknown-none-elf", sparc_unknown_none_elf),
+
     ("loongarch64-unknown-none", loongarch64_unknown_none),
     ("loongarch64-unknown-none-softfloat", loongarch64_unknown_none_softfloat),
 

compiler/rustc_target/src/spec/sparc_unknown_none_elf.rs

@@ -0,0 +1,27 @@
+use crate::abi::Endian;
+use crate::spec::{Cc, LinkerFlavor, Lld, PanicStrategy, RelocModel, Target, TargetOptions};
+
+pub fn target() -> Target {
+    let options = TargetOptions {
+        linker_flavor: LinkerFlavor::Gnu(Cc::Yes, Lld::No),
+        linker: Some("sparc-elf-gcc".into()),
+        endian: Endian::Big,
+        cpu: "v7".into(),
+        abi: "elf".into(),
+        max_atomic_width: Some(32),
+        atomic_cas: true,
+        panic_strategy: PanicStrategy::Abort,
+        relocation_model: RelocModel::Static,
+        no_default_libraries: false,
+        emit_debug_gdb_scripts: false,
+        eh_frame_header: false,
+        ..Default::default()
+    };
+    Target {
+        data_layout: "E-m:e-p:32:32-i64:64-f128:64-n32-S64".into(),
+        llvm_target: "sparc-unknown-none-elf".into(),
+        pointer_width: 32,
+        arch: "sparc".into(),
+        options,
+    }
+}

src/doc/rustc/src/SUMMARY.md

@@ -38,6 +38,7 @@
     - [mipsel-sony-psx](platform-support/mipsel-sony-psx.md)
     - [nvptx64-nvidia-cuda](platform-support/nvptx64-nvidia-cuda.md)
     - [riscv32imac-unknown-xous-elf](platform-support/riscv32imac-unknown-xous-elf.md)
+    - [sparc-unknown-none-elf](./platform-support/sparc-unknown-none-elf.md)
     - [*-pc-windows-gnullvm](platform-support/pc-windows-gnullvm.md)
     - [\*-nto-qnx-\*](platform-support/nto-qnx.md)
     - [\*-unknown-netbsd\*](platform-support/netbsd.md)

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

@@ -176,6 +176,7 @@ target | std | notes
 `thumbv8m.base-none-eabi` | * | Bare ARMv8-M Baseline
 `thumbv8m.main-none-eabi` | * | Bare ARMv8-M Mainline
 `thumbv8m.main-none-eabihf` | * | Bare ARMv8-M Mainline, hardfloat
+[`sparc-unknown-none-elf`](./platform-support/sparc-unknown-none-elf.md) | * | Bare 32-bit SPARC V7+
 `wasm32-unknown-emscripten` | ✓ | WebAssembly via Emscripten
 `wasm32-unknown-unknown` | ✓ | WebAssembly
 `wasm32-wasi` | ✓ | WebAssembly with WASI

src/doc/rustc/src/platform-support/sparc-unknown-none-elf.md

@@ -0,0 +1,188 @@
+# `sparc-unknown-none-elf`
+
+**Tier: 3**
+
+Rust for bare-metal 32-bit SPARC V7 and V8 systems, e.g. the Gaisler LEON3.
+
+| Target                 | Descriptions                              |
+| ---------------------- | ----------------------------------------- |
+| sparc-unknown-none-elf | SPARC V7 32-bit (freestanding, hardfloat) |
+
+## Target maintainers
+
+- Jonathan Pallant, <[email protected]>, https://ferrous-systems.com
+
+## Requirements
+
+This target is cross-compiled. There is no support for `std`. There is no
+default allocator, but it's possible to use `alloc` by supplying an allocator.
+
+By default, code generated with this target should run on any `SPARC` hardware;
+enabling additional target features may raise this baseline.
+
+- `-Ctarget-cpu=v8` adds the extra SPARC V8 instructions.
+
+- `-Ctarget-cpu=leon3` adds the SPARC V8 instructions and sets up scheduling to
+  suit the Gaisler Leon3.
+
+Functions marked `extern "C"` use the [standard SPARC architecture calling
+convention](https://sparc.org/technical-documents/).
+
+This target generates ELF binaries. Any alternate formats or special
+considerations for binary layout will require linker options or linker scripts.
+
+## Building the target
+
+You can build Rust with support for the target by adding it to the `target`
+list in `config.toml`:
+
+```toml
+[build]
+build-stage = 1
+host = ["<target for your host>"]
+target = ["<target for your host>", "sparc-unknown-none-elf"]
+```
+
+Replace `<target for your host>` with `x86_64-unknown-linux-gnu` or whatever
+else is appropriate for your host machine.
+
+## Building Rust programs
+
+To build with this target, pass it to the `--target` argument, like:
+
+```console
+cargo build --target sparc-unknown-none-elf
+```
+
+This target uses GCC as a linker, and so you will need an appropriate GCC
+compatible `sparc-unknown-none` toolchain. The default linker binary is
+`sparc-elf-gcc`, but you can override this in your project configuration, as
+follows:
+
+`.cargo/config.toml`:
+```toml
+[target.sparc-unknown-none-elf]
+linker = "sparc-custom-elf-gcc"
+```
+
+## Testing
+
+As `sparc-unknown-none-elf` supports a variety of different environments and does
+not support `std`, this target does not support running the Rust test suite.
+
+## Cross-compilation toolchains and C code
+
+This target was initially tested using [BCC2] from Gaisler, along with the TSIM
+Leon3 processor simulator. Both [BCC2] GCC and [BCC2] Clang have been shown to
+work. To work with these tools, your project configuration should contain
+something like:
+
+[BCC2]: https://www.gaisler.com/index.php/downloads/compilers
+
+`.cargo/config.toml`:
+```toml
+[target.sparc-unknown-none-elf]
+linker = "sparc-gaisler-elf-gcc"
+runner = "tsim-leon3"
+
+[build]
+target = ["sparc-unknown-none-elf"]
+rustflags = "-Ctarget-cpu=leon3"
+```
+
+With this configuration, running `cargo run` will compile your code for the
+SPARC V8 compatible Gaisler Leon3 processor and then start the `tsim-leon3`
+simulator. The `libcore` was pre-compiled as part of the `rustc` compilation
+process using the SPARC V7 baseline, but if you are using a nightly toolchain
+you can use the
+[`-Z build-std=core`](https://doc.rust-lang.org/cargo/reference/unstable.html#build-std)
+option to rebuild `libcore` from source. This may be useful if you want to
+compile it for SPARC V8 and take advantage of the extra instructions.
+
+`.cargo/config.toml`:
+```toml
+[target.sparc-unknown-none-elf]
+linker = "sparc-gaisler-elf-gcc"
+runner = "tsim-leon3"
+
+[build]
+target = ["sparc-unknown-none-elf"]
+rustflags = "-Ctarget-cpu=leon3"
+
+[unstable]
+build-std = ["core"]
+```
+
+Either way, once the simulator is running, simply enter the command `run` to
+start the code executing in the simulator.
+
+The default C toolchain libraries are linked in, so with the Gaisler [BCC2]
+toolchain, and using its default Leon3 BSP, you can use call the C `putchar`
+function and friends to output to the simulator console. The default linker
+script is also appropriate for the Leon3 simulator, so no linker script is
+required.
+
+Here's a complete example using the above config file:
+
+```rust,ignore (cannot-test-this-because-it-assumes-special-libc-functions)
+#![no_std]
+#![no_main]
+
+extern "C" {
+    fn putchar(ch: i32);
+    fn _exit(code: i32) -> !;
+}
+
+#[no_mangle]
+extern "C" fn main() -> i32 {
+    let message = "Hello, this is Rust!";
+    for b in message.bytes() {
+        unsafe {
+            putchar(b as i32);
+        }
+    }
+    0
+}
+
+#[panic_handler]
+fn panic(_panic: &core::panic::PanicInfo) -> ! {
+    unsafe {
+        _exit(1);
+    }
+}
+```
+
+```console
+$ cargo run --target=sparc-unknown-none-elf
+   Compiling sparc-demo-rust v0.1.0 (/work/sparc-demo-rust)
+    Finished dev [unoptimized + debuginfo] target(s) in 3.44s
+     Running `tsim-leon3 target/sparc-unknown-none-elf/debug/sparc-demo-rust`
+
+ TSIM3 LEON3 SPARC simulator, version 3.1.9 (evaluation version)
+
+ Copyright (C) 2023, Frontgrade Gaisler - all rights reserved.
+ This software may only be used with a valid license.
+ For latest updates, go to https://www.gaisler.com/
+ Comments or bug-reports to [email protected]
+
+ This TSIM evaluation version will expire 2023-11-28
+
+Number of CPUs: 2
+system frequency: 50.000 MHz
+icache: 1 * 4 KiB, 16 bytes/line (4 KiB total)
+dcache: 1 * 4 KiB, 16 bytes/line (4 KiB total)
+Allocated 8192 KiB SRAM memory, in 1 bank at 0x40000000
+Allocated 32 MiB SDRAM memory, in 1 bank at 0x60000000
+Allocated 8192 KiB ROM memory at 0x00000000
+section: .text, addr: 0x40000000, size: 20528 bytes
+section: .rodata, addr: 0x40005030, size: 128 bytes
+section: .data, addr: 0x400050b0, size: 1176 bytes
+read 347 symbols
+
+tsim> run
+  Initializing and starting from 0x40000000
+Hello, this is Rust!
+
+  Program exited normally on CPU 0.
+tsim>
+```

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

@@ -127,6 +127,7 @@ static TARGETS: &[&str] = &[
     "s390x-unknown-linux-gnu",
     "sparc64-unknown-linux-gnu",
     "sparcv9-sun-solaris",
+    "sparc-unknown-none-elf",
     "thumbv6m-none-eabi",
     "thumbv7em-none-eabi",
     "thumbv7em-none-eabihf",