Add an target to support the Cortex-R52.

Author: chrisnc

Diff for: compiler/rustc_target/src/spec/armv8r_none_eabihf.rs

@@ -0,0 +1,35 @@
+// Targets the Little-endian Cortex-R52 processor (ARMv8-R)
+
+use crate::spec::{Cc, LinkerFlavor, Lld, PanicStrategy, RelocModel, Target, TargetOptions};
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "armv8r-none-eabihf".into(),
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".into(),
+        arch: "arm".into(),
+
+        options: TargetOptions {
+            abi: "eabihf".into(),
+            linker_flavor: LinkerFlavor::Gnu(Cc::No, Lld::Yes),
+            linker: Some("rust-lld".into()),
+            relocation_model: RelocModel::Static,
+            panic_strategy: PanicStrategy::Abort,
+            // The Cortex-R52 has two variants with respect to floating-point support:
+            // 1. fp-armv8, SP-only, with 16 DP (32 SP) registers
+            // 2. neon-fp-armv8, SP+DP, with 32 DP registers
+            // Use the lesser of these two options as the default, as it will produce code
+            // compatible with either variant.
+            //
+            // Reference:
+            // Arm Cortex-R52 Processor Technical Reference Manual
+            // - Chapter 15 Advanced SIMD and floating-point support
+            features: "+fp-armv8,-fp64,-d32".into(),
+            max_atomic_width: Some(64),
+            emit_debug_gdb_scripts: false,
+            // GCC defaults to 8 for arm-none here.
+            c_enum_min_bits: Some(8),
+            ..Default::default()
+        },
+    }
+}

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

@@ -1543,6 +1543,7 @@ supported_targets! {
     ("armebv7r-none-eabihf", armebv7r_none_eabihf),
     ("armv7r-none-eabi", armv7r_none_eabi),
     ("armv7r-none-eabihf", armv7r_none_eabihf),
+    ("armv8r-none-eabihf", armv8r_none_eabihf),
 
     ("x86_64-pc-solaris", x86_64_pc_solaris),
     ("sparcv9-sun-solaris", sparcv9_sun_solaris),

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

@@ -160,6 +160,7 @@ target | std | notes
 [`armv7a-none-eabi`](platform-support/arm-none-eabi.md) | * | Bare ARMv7-A
 [`armv7r-none-eabi`](platform-support/armv7r-none-eabi.md) | * | Bare ARMv7-R
 [`armv7r-none-eabihf`](platform-support/armv7r-none-eabi.md) | * | Bare ARMv7-R, hardfloat
+`armv8r-none-eabihf` | * | Bare ARMv8-R, hardfloat
 `i586-pc-windows-msvc` | * | 32-bit Windows w/o SSE [^x86_32-floats-x87]
 `i586-unknown-linux-gnu` | ✓ | 32-bit Linux w/o SSE (kernel 3.2, glibc 2.17) [^x86_32-floats-x87]
 `i586-unknown-linux-musl` | ✓ | 32-bit Linux w/o SSE, MUSL [^x86_32-floats-x87]

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

@@ -13,6 +13,7 @@
 - [{arm,thumb}v4t-none-eabi](armv4t-none-eabi.md)
 - [{arm,thumb}v5te-none-eabi](armv5te-none-eabi.md)
 - armv7a-none-eabihf
+- [armv8r-none-eabihf](armv8r-none-eabihf.md)
 
 Bare-metal target for 32-bit ARM CPUs.
 

Diff for: src/doc/rustc/src/platform-support/armv8r-none-eabihf.md

@@ -0,0 +1,40 @@
+# `armv8r-none-eabihf`
+
+**Tier: 3**
+
+Bare-metal target for CPUs in the ARMv8-R architecture family, supporting
+dual ARM/Thumb mode, with ARM mode as the default.
+
+Processors in this family include the Arm [Cortex-R52][cortex-r52]
+and [Cortex-R52+][cortex-r52-plus].
+
+See [`arm-none-eabi`](arm-none-eabi.md) for information applicable to all
+`arm-none-eabi` targets.
+
+[cortex-r52]: https://www.arm.com/products/silicon-ip-cpu/cortex-r/cortex-r52
+[cortex-r52-plus]: https://www.arm.com/products/silicon-ip-cpu/cortex-r/cortex-r52-plus
+
+## Target maintainers
+
+- [Chris Copeland](https://github.com./chrisnc), `[email protected]`
+
+## Requirements
+
+The Cortex-R52 family always includes a floating-point unit, so there is no
+non-`hf` version of this target. The floating-point features assumed by this
+target are those of the single-precision-only config of the Cortex-R52, which
+has 16 double-precision registers, accessible as 32 single-precision registers.
+The other variant of Cortex-R52 includes double-precision, 32 double-precision
+registers, and Advanced SIMD (Neon).
+
+The manual refers to this as the "Full Advanced SIMD config". To compile code
+for this variant, use: `-C target-feature=+fp64,+d32,+neon`. See the [Advanced
+SIMD and floating-point support][fpu] section of the Cortex-R52 Processor
+Technical Reference Manual for more details.
+
+[fpu]: https://developer.arm.com/documentation/100026/0104/Advanced-SIMD-and-floating-point-support/About-the-Advanced-SIMD-and-floating-point-support
+
+## Cross-compilation toolchains and C code
+
+This target supports C code compiled with the `arm-none-eabi` target triple and
+`-march=armv8-r` or a suitable `-mcpu` flag.

Diff for: src/tools/build-manifest/src/main.rs

@@ -83,6 +83,7 @@ static TARGETS: &[&str] = &[
     "armebv7r-none-eabihf",
     "armv7r-none-eabi",
     "armv7r-none-eabihf",
+    "armv8r-none-eabihf",
     "armv7s-apple-ios",
     "bpfeb-unknown-none",
     "bpfel-unknown-none",