Add {thumb,arm}v5te-none-eabi targets

Author: QuinnPainter

Diff for: compiler/rustc_target/src/spec/armv5te_none_eabi.rs

@@ -0,0 +1,50 @@
+//! Targets the ARMv5TE, with code as `a32` code by default.
+
+use crate::spec::{
+    cvs, LinkerFlavor, LldFlavor, PanicStrategy, RelocModel, Target, TargetOptions
+};
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "armv5te-none-eabi".into(),
+        pointer_width: 32,
+        arch: "arm".into(),
+        /* Data layout args are '-' separated:
+         * little endian
+         * stack is 64-bit aligned (EABI)
+         * pointers are 32-bit
+         * i64 must be 64-bit aligned (EABI)
+         * mangle names with ELF style
+         * native integers are 32-bit
+         * All other elements are default
+         */
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".into(),
+
+        options: TargetOptions {
+            abi: "eabi".into(),
+            linker_flavor: LinkerFlavor::Lld(LldFlavor::Ld),
+            linker: Some("rust-lld".into()),
+            // extra args passed to the external assembler (assuming `arm-none-eabi-as`):
+            // * activate t32/a32 interworking
+            // * use arch ARMv5TE
+            // * use little-endian
+            asm_args: cvs!["-mthumb-interwork", "-march=armv5te", "-mlittle-endian",],
+            // minimum extra features, these cannot be disabled via -C
+            // Also force-enable 32-bit atomics, which allows the use of atomic load/store only.
+            // The resulting atomics are ABI incompatible with atomics backed by libatomic.
+            features: "+soft-float,+strict-align,+atomics-32".into(),
+            main_needs_argc_argv: false,
+            // don't have atomic compare-and-swap
+            atomic_cas: false,
+            has_thumb_interworking: true,
+            relocation_model: RelocModel::Static,
+            panic_strategy: PanicStrategy::Abort,
+            // from thumb_base, rust-lang/rust#44993.
+            emit_debug_gdb_scripts: false,
+            // from thumb_base, apparently gcc/clang give enums a minimum of 8 bits on no-os targets
+            c_enum_min_bits: 8,
+
+            ..Default::default()
+        },
+    }
+}

Diff for: compiler/rustc_target/src/spec/mod.rs

@@ -1082,6 +1082,8 @@ supported_targets! {
     ("mipsel-unknown-none", mipsel_unknown_none),
     ("thumbv4t-none-eabi", thumbv4t_none_eabi),
     ("armv4t-none-eabi", armv4t_none_eabi),
+    ("thumbv5te-none-eabi", thumbv5te_none_eabi),
+    ("armv5te-none-eabi", armv5te_none_eabi),
 
     ("aarch64_be-unknown-linux-gnu", aarch64_be_unknown_linux_gnu),
     ("aarch64-unknown-linux-gnu_ilp32", aarch64_unknown_linux_gnu_ilp32),

Diff for: compiler/rustc_target/src/spec/thumbv5te_none_eabi.rs

@@ -0,0 +1,41 @@
+//! Targets the ARMv5TE, with code as `t32` code by default.
+
+use crate::spec::{cvs, FramePointer, Target, TargetOptions};
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "thumbv5te-none-eabi".into(),
+        pointer_width: 32,
+        arch: "arm".into(),
+        /* Data layout args are '-' separated:
+         * little endian
+         * stack is 64-bit aligned (EABI)
+         * pointers are 32-bit
+         * i64 must be 64-bit aligned (EABI)
+         * mangle names with ELF style
+         * native integers are 32-bit
+         * All other elements are default
+         */
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".into(),
+
+        options: TargetOptions {
+            abi: "eabi".into(),
+            // extra args passed to the external assembler (assuming `arm-none-eabi-as`):
+            // * activate t32/a32 interworking
+            // * use arch ARMv5TE
+            // * use little-endian
+            asm_args: cvs!["-mthumb-interwork", "-march=armv5te", "-mlittle-endian",],
+            // minimum extra features, these cannot be disabled via -C
+            // Also force-enable 32-bit atomics, which allows the use of atomic load/store only.
+            // The resulting atomics are ABI incompatible with atomics backed by libatomic.
+            features: "+soft-float,+strict-align,+atomics-32".into(),
+            frame_pointer: FramePointer::MayOmit,
+            main_needs_argc_argv: false,
+            // don't have atomic compare-and-swap
+            atomic_cas: false,
+            has_thumb_interworking: true,
+
+            ..super::thumb_base::opts()
+        },
+    }
+}

Diff for: src/doc/rustc/src/SUMMARY.md

@@ -19,6 +19,7 @@
     - [\*-apple-watchos\*](platform-support/apple-watchos.md)
     - [aarch64-nintendo-switch-freestanding](platform-support/aarch64-nintendo-switch-freestanding.md)
     - [armv4t-none-eabi](platform-support/armv4t-none-eabi.md)
+    - [armv5te-none-eabi](platform-support/armv5te-none-eabi.md)
     - [armv6k-nintendo-3ds](platform-support/armv6k-nintendo-3ds.md)
     - [armv7-unknown-linux-uclibceabi](platform-support/armv7-unknown-linux-uclibceabi.md)
     - [armv7-unknown-linux-uclibceabihf](platform-support/armv7-unknown-linux-uclibceabihf.md)

Diff for: src/doc/rustc/src/platform-support.md

@@ -225,6 +225,7 @@ target | std | host | notes
 [`arm64_32-apple-watchos`](platform-support/apple-watchos.md) | ✓ | | ARM Apple WatchOS 64-bit with 32-bit pointers
 `armv4t-none-eabi` | * |  | ARMv4T A32
 `armv4t-unknown-linux-gnueabi` | ? |  |
+[`armv5te-none-eabi`](platform-support/armv5te-none-eabi.md) | * | | ARMv5TE A32
 `armv5te-unknown-linux-uclibceabi` | ? |  | ARMv5TE Linux with uClibc
 `armv6-unknown-freebsd` | ✓ | ✓ | ARMv6 FreeBSD
 `armv6-unknown-netbsd-eabihf` | ? |  |
@@ -291,6 +292,7 @@ target | std | host | notes
 `sparc64-unknown-netbsd` | ✓ | ✓ | NetBSD/sparc64
 [`sparc64-unknown-openbsd`](platform-support/openbsd.md) | ✓ | ✓ | OpenBSD/sparc64
 `thumbv4t-none-eabi` | * |  | ARMv4T T32
+[`thumbv5te-none-eabi`](platform-support/armv5te-none-eabi.md) | * | | ARMv5TE T32
 `thumbv7a-pc-windows-msvc` | ? |  |
 `thumbv7a-uwp-windows-msvc` | ✓ |  |
 `thumbv7neon-unknown-linux-musleabihf` | ? |  | Thumb2-mode ARMv7a Linux with NEON, MUSL

Diff for: src/doc/rustc/src/platform-support/armv5te-none-eabi.md

@@ -0,0 +1,75 @@
+# `armv5te-none-eabi`
+
+**Tier: 3**
+
+Bare-metal target for any cpu in the ARMv5TE architecture family, supporting
+ARM/Thumb code interworking (aka `a32`/`t32`), with ARM code as the default code
+generation.
+
+The `thumbv5te-none-eabi` target is the same as this one, but with THUMB code as the default.
+
+In particular this supports the main CPU of the Nintendo DS, but there's nothing DS
+specific with this target, so any ARMv5TE device should work fine.
+
+## Target Maintainers
+
+* [@QuinnPainter](https://github.com/QuinnPainter)
+
+## Requirements
+
+The target is cross-compiled, and uses static linking.
+
+By default, the `lld` linker included with Rust will be used.
+
+However, you may want to use the `arm-none-eabi-ld` linker instead. This can be obtained for Windows/Mac/Linux from the [ARM
+Developer Website][arm-dev], or possibly from your OS's package manager. To use it, add the following to your `.cargo/config.toml`:
+
+```toml
+[target.armv5te-none-eabi]
+linker = "arm-none-eabi-ld"
+```
+
+[arm-dev]: https://developer.arm.com/Tools%20and%20Software/GNU%20Toolchain
+
+This target doesn't provide a linker script, you'll need to bring your own
+according to the specific device you want to target. Pass
+`-Clink-arg=-Tyour_script.ld` as a rustc argument to make the linker use
+`your_script.ld` during linking.
+
+## Building Rust Programs
+
+Because it is Tier 3, rust does not yet ship pre-compiled artifacts for this target.
+
+Just use the `build-std` nightly cargo feature to build the `core` library. You
+can pass this as a command line argument to cargo, or your `.cargo/config.toml`
+file might include the following lines:
+
+```toml
+[unstable]
+build-std = ["core"]
+```
+
+Most of `core` should work as expected, with the following notes:
+* the target is "soft float", so `f32` and `f64` operations are emulated in
+  software.
+* integer division is also emulated in software.
+* the target is old enough that it doesn't have atomic instructions.
+
+`alloc` is also supported, as long as you provide your own global allocator.
+
+Rust programs are output as ELF files.
+
+For running on DS hardware, you'll need to use an external tool to bundle this ELF file into an NDS binary. The `ndstool` utility included with devkitARM is one such tool that can do this for you:
+
+```shell
+ndstool -c [out_nds] -9 [in_elf]
+```
+
+## Testing
+
+This is a cross-compiled target that you will need to emulate during testing.
+
+Because this is a device-agnostic target, and the exact emulator that you'll
+need depends on the specific device you want to run your code on.
+
+For example, when programming for the DS, you can use one of the several available DS emulators, such as [melonDS](https://melonds.kuribo64.net/).