From 6642b4b1e2f2edec71cdf3fabef8fcdc8b8517a7 Mon Sep 17 00:00:00 2001
From: Havard Eidnes <he@NetBSD.org>
Date: Wed, 25 Oct 2023 15:23:34 +0000
Subject: [PATCH] Add support for i586-unknown-netbsd as target.

This restricts instructions to those offered by Pentium,
to support e.g. AMD Geode.

There is already an entry for this target in the NetBSD
platform support page at

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

...so this should forestall its removal.

Additional fixes are needed for some vendored modules, this
is the changes in the rust compiler core itself.
---
 compiler/rustc_llvm/build.rs                  |  6 +++++
 .../src/spec/i586_unknown_netbsd.rs           | 22 +++++++++++++++++++
 compiler/rustc_target/src/spec/mod.rs         |  1 +
 3 files changed, 29 insertions(+)
 create mode 100644 compiler/rustc_target/src/spec/i586_unknown_netbsd.rs

diff --git a/compiler/rustc_llvm/build.rs b/compiler/rustc_llvm/build.rs
index f606fa483caf..acb1d9607a4f 100644
--- a/compiler/rustc_llvm/build.rs
+++ b/compiler/rustc_llvm/build.rs
@@ -258,6 +258,12 @@ fn main() {
     {
         println!("cargo:rustc-link-lib=z");
     } else if target.contains("netbsd") {
+        // Building for i586 or i686, we need -latomic for 64-bit atomics
+        if target.starts_with("i586")
+           || target.starts_with("i686")
+        {
+            println!("cargo:rustc-link-lib=atomic");
+        }
         println!("cargo:rustc-link-lib=z");
         println!("cargo:rustc-link-lib=execinfo");
     }
diff --git a/compiler/rustc_target/src/spec/i586_unknown_netbsd.rs b/compiler/rustc_target/src/spec/i586_unknown_netbsd.rs
new file mode 100644
index 000000000000..9b36a3c28d35
--- /dev/null
+++ b/compiler/rustc_target/src/spec/i586_unknown_netbsd.rs
@@ -0,0 +1,22 @@
+use crate::spec::{Cc, Lld, LinkerFlavor, StackProbeType, Target, TargetOptions};
+
+pub fn target() -> Target {
+    let mut base = super::netbsd_base::opts();
+    base.cpu = "pentium".into();
+    base.max_atomic_width = Some(64);
+    base.pre_link_args
+        .entry(LinkerFlavor::Gnu(Cc::Yes, Lld::No))
+        .or_default()
+        .push("-m32".into());
+    base.stack_probes = StackProbeType::Call;
+
+    Target {
+        llvm_target: "i586-unknown-netbsdelf".into(),
+        pointer_width: 32,
+        data_layout: "e-m:e-p:32:32-p270:32:32-p271:32:32-p272:64:64-\
+            f64:32:64-f80:32-n8:16:32-S128"
+            .into(),
+        arch: "x86".into(),
+        options: TargetOptions { mcount: "__mcount".into(), ..base },
+    }
+}
diff --git a/compiler/rustc_target/src/spec/mod.rs b/compiler/rustc_target/src/spec/mod.rs
index f1c7513d8856..73e5c6c858b9 100644
--- a/compiler/rustc_target/src/spec/mod.rs
+++ b/compiler/rustc_target/src/spec/mod.rs
@@ -1426,6 +1426,7 @@ fn $module() {
     ("aarch64_be-unknown-netbsd", aarch64_be_unknown_netbsd),
     ("armv6-unknown-netbsd-eabihf", armv6_unknown_netbsd_eabihf),
     ("armv7-unknown-netbsd-eabihf", armv7_unknown_netbsd_eabihf),
+    ("i586-unknown-netbsd", i586_unknown_netbsd),
     ("i686-unknown-netbsd", i686_unknown_netbsd),
     ("powerpc-unknown-netbsd", powerpc_unknown_netbsd),
     ("riscv64gc-unknown-netbsd", riscv64gc_unknown_netbsd),