Add support for riscv64gc-unknown-freebsd

compiler/rustc_llvm/build.rs

@@ -276,8 +276,11 @@ fn main() {
         "stdc++"
     };
 
-    // RISC-V requires libatomic for sub-word atomic operations
-    if target.starts_with("riscv") {
+    // RISC-V GCC erroneously requires libatomic for sub-word
+    // atomic operations. FreeBSD uses Clang as its system
+    // compiler and provides no libatomic in its base system so
+    // does not want this.
+    if !target.contains("freebsd") && target.starts_with("riscv") {
         println!("cargo:rustc-link-lib=atomic");
     }
 

compiler/rustc_target/src/spec/mod.rs

@@ -813,6 +813,7 @@ supported_targets! {
     ("powerpc-unknown-freebsd", powerpc_unknown_freebsd),
     ("powerpc64-unknown-freebsd", powerpc64_unknown_freebsd),
     ("powerpc64le-unknown-freebsd", powerpc64le_unknown_freebsd),
+    ("riscv64gc-unknown-freebsd", riscv64gc_unknown_freebsd),
     ("x86_64-unknown-freebsd", x86_64_unknown_freebsd),
 
     ("x86_64-unknown-dragonfly", x86_64_unknown_dragonfly),

compiler/rustc_target/src/spec/riscv64gc_unknown_freebsd.rs

@@ -0,0 +1,18 @@
+use crate::spec::{CodeModel, Target, TargetOptions};
+
+pub fn target() -> Target {
+    Target {
+        llvm_target: "riscv64-unknown-freebsd".to_string(),
+        pointer_width: 64,
+        data_layout: "e-m:e-p:64:64-i64:64-i128:128-n64-S128".to_string(),
+        arch: "riscv64".to_string(),
+        options: TargetOptions {
+            code_model: Some(CodeModel::Medium),
+            cpu: "generic-rv64".to_string(),
+            features: "+m,+a,+f,+d,+c".to_string(),
+            llvm_abiname: "lp64d".to_string(),
+            max_atomic_width: Some(64),
+            ..super::freebsd_base::opts()
+        },
+    }
+}

library/std/src/os/raw/mod.rs

@@ -69,7 +69,8 @@ type_alias! { "char.md", c_char = u8, NonZero_c_char = NonZeroU8;
             target_arch = "aarch64",
             target_arch = "arm",
             target_arch = "powerpc",
-            target_arch = "powerpc64"
+            target_arch = "powerpc64",
+            target_arch = "riscv64"
         )
     ),
     all(
@@ -112,7 +113,8 @@ type_alias! { "char.md", c_char = i8, NonZero_c_char = NonZeroI8;
             target_arch = "aarch64",
             target_arch = "arm",
             target_arch = "powerpc",
-            target_arch = "powerpc64"
+            target_arch = "powerpc64",
+            target_arch = "riscv64"
         )
     ),
     all(

src/bootstrap/bootstrap.py

@@ -265,7 +265,7 @@ def default_build_triple(verbose):
         err = "unknown OS type: {}".format(ostype)
         sys.exit(err)
 
-    if cputype == 'powerpc' and ostype == 'unknown-freebsd':
+    if cputype in ['powerpc', 'riscv'] and ostype == 'unknown-freebsd':
         cputype = subprocess.check_output(
               ['uname', '-p']).strip().decode(default_encoding)
     cputype_mapper = {

src/bootstrap/native.rs

@@ -249,9 +249,14 @@ impl Step for Llvm {
             }
         }
 
-        if target.starts_with("riscv") {
-            // In RISC-V, using C++ atomics require linking to `libatomic` but the LLVM build
-            // system check cannot detect this. Therefore it is set manually here.
+        if !target.contains("freebsd") && target.starts_with("riscv") {
+            // RISC-V GCC erroneously requires linking against
+            // `libatomic` when using 1-byte and 2-byte C++
+            // atomics but the LLVM build system check cannot
+            // detect this. Therefore it is set manually here.
+            // FreeBSD uses Clang as its system compiler and
+            // provides no libatomic in its base system so does
+            // not want this.
             if !builder.config.llvm_tools_enabled {
                 cfg.define("CMAKE_EXE_LINKER_FLAGS", "-latomic");
             } else {

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

@@ -267,6 +267,7 @@ target | std | host | notes
 `riscv32gc-unknown-linux-gnu` |   |   | RISC-V Linux (kernel 5.4, glibc 2.33)
 `riscv32gc-unknown-linux-musl` |   |   | RISC-V Linux (kernel 5.4, musl + RISCV32 support patches)
 `riscv32imc-esp-espidf` | ✓ |  | RISC-V ESP-IDF
+`riscv64gc-unknown-freebsd` |   |   | RISC-V FreeBSD
 `riscv64gc-unknown-linux-musl` |   |   | RISC-V Linux (kernel 4.20, musl 1.2.0)
 `s390x-unknown-linux-musl` |  |  | S390x Linux (kernel 2.6.32, MUSL)
 `sparc-unknown-linux-gnu` | ✓ |  | 32-bit SPARC Linux