Auto merge of #126907 - glaubitz:sparc-fixes, r=nagisa

Fixes for 32-bit SPARC on Linux

This PR fixes a number of issues which previously prevented `rustc` from being built
successfully for 32-bit SPARC using the `sparc-unknown-linux-gnu` triplet.

In particular, it adds linking against `libatomic` where necessary, uses portable `AtomicU64`
for `rustc_data_structures` and rewrites the spec for `sparc_unknown_linux_gnu` to use
`TargetOptions` and replaces the previously used `-mv8plus` with the more portable
`-mcpu=v9 -m32`.

To make `rustc` build successfully, support for 32-bit SPARC needs to be added to the `object`
crate as well as the `nix` crate which I will be sending out later as well.

r? nagisa

compiler/rustc_data_structures/Cargo.toml

@@ -50,7 +50,7 @@ libc = "0.2"
 memmap2 = "0.2.1"
 # tidy-alphabetical-end
 
-[target.'cfg(any(target_arch = "powerpc", target_arch = "mips"))'.dependencies]
+[target.'cfg(any(target_arch = "mips", target_arch = "powerpc", target_arch = "sparc"))'.dependencies]
 portable-atomic = "1.5.1"
 
 [features]

compiler/rustc_data_structures/src/marker.rs

@@ -147,14 +147,14 @@ cfg_match! {
             [crate::owned_slice::OwnedSlice]
         );
 
-        // PowerPC and MIPS platforms with 32-bit pointers do not
+        // MIPS, PowerPC and SPARC platforms with 32-bit pointers do not
         // have AtomicU64 type.
-        #[cfg(not(any(target_arch = "powerpc", target_arch = "mips")))]
+        #[cfg(not(any(target_arch = "powerpc", target_arch = "powerpc", target_arch = "sparc")))]
         already_sync!(
             [std::sync::atomic::AtomicU64]
         );
 
-        #[cfg(any(target_arch = "powerpc", target_arch = "mips"))]
+        #[cfg(any(target_arch = "mips", target_arch = "powerpc", target_arch = "sparc"))]
         already_sync!(
             [portable_atomic::AtomicU64]
         );

compiler/rustc_data_structures/src/sync.rs

@@ -270,12 +270,12 @@ cfg_match! {
 
         pub use std::sync::atomic::{AtomicBool, AtomicUsize, AtomicU32};
 
-        // PowerPC and MIPS platforms with 32-bit pointers do not
+        // MIPS, PowerPC and SPARC platforms with 32-bit pointers do not
         // have AtomicU64 type.
-        #[cfg(not(any(target_arch = "powerpc", target_arch = "mips")))]
+        #[cfg(not(any(target_arch = "mips", target_arch = "powerpc", target_arch = "sparc")))]
         pub use std::sync::atomic::AtomicU64;
 
-        #[cfg(any(target_arch = "powerpc", target_arch = "mips"))]
+        #[cfg(any(target_arch = "mips", target_arch = "powerpc", target_arch = "sparc"))]
         pub use portable_atomic::AtomicU64;
 
         pub use std::sync::Arc as Lrc;

compiler/rustc_llvm/build.rs

@@ -235,6 +235,7 @@ fn main() {
         || target.starts_with("mips-")
         || target.starts_with("mipsel-")
         || target.starts_with("powerpc-")
+        || target.starts_with("sparc-")
     {
         // 32-bit targets need to link libatomic.
         println!("cargo:rustc-link-lib=atomic");

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

@@ -1,13 +1,7 @@
 use crate::abi::Endian;
-use crate::spec::{base, Cc, LinkerFlavor, Lld, Target};
+use crate::spec::{base, Cc, LinkerFlavor, Lld, Target, TargetOptions};
 
 pub fn target() -> Target {
-    let mut base = base::linux_gnu::opts();
-    base.endian = Endian::Big;
-    base.cpu = "v9".into();
-    base.max_atomic_width = Some(32);
-    base.add_pre_link_args(LinkerFlavor::Gnu(Cc::Yes, Lld::No), &["-mv8plus"]);
-
     Target {
         llvm_target: "sparc-unknown-linux-gnu".into(),
         metadata: crate::spec::TargetMetadata {
@@ -19,6 +13,15 @@ pub fn target() -> Target {
         pointer_width: 32,
         data_layout: "E-m:e-p:32:32-i64:64-f128:64-n32-S64".into(),
         arch: "sparc".into(),
-        options: base,
+        options: TargetOptions {
+            cpu: "v9".into(),
+            endian: Endian::Big,
+            late_link_args: TargetOptions::link_args(
+                LinkerFlavor::Gnu(Cc::Yes, Lld::No),
+                &["-mcpu=v9", "-m32"],
+            ),
+            max_atomic_width: Some(32),
+            ..base::linux_gnu::opts()
+        },
     }
 }

src/bootstrap/src/core/build_steps/llvm.rs

@@ -407,18 +407,21 @@ impl Step for Llvm {
             cfg.define("LLVM_LINK_LLVM_DYLIB", "ON");
         }
 
-        if (target.starts_with("riscv") || target.starts_with("csky"))
+        if (target.starts_with("csky")
+            || target.starts_with("riscv")
+            || target.starts_with("sparc-"))
             && !target.contains("freebsd")
             && !target.contains("openbsd")
             && !target.contains("netbsd")
         {
-            // RISC-V and CSKY GCC erroneously requires linking against
+            // CSKY and 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.
             // Some BSD uses Clang as its system compiler and
             // provides no libatomic in its base system so does
-            // not want this.
+            // not want this. 32-bit SPARC requires linking against
+            // libatomic as well.
             ldflags.exe.push(" -latomic");
             ldflags.shared.push(" -latomic");
         }