From 06704919507893e4e26a3fc0adf5aefaf0356199 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov@redhat.com>
Date: Thu, 12 Mar 2026 03:52:53 -0500
Subject: [PATCH] Don't add empty target features for target-cpu=native on
 macOS

LLVM does not support host feature detection (only host cpu
detection) on apple platforms. As such, the returned feature
string will be empty. Adding this empty string to the target-features
attribute results in a verifier error on LLVM 22.

Fix this by not adding the empty string to the target features.
The reason why this was not caught by the target-cpu-native test
is that it requires a function that adds *some* target features,
otherwise the attribute is omitted entirely. We achieve this with
a somewhat peculiar construction that enables `neon` if it's
already enabled. (This is to avoid enabling it on softfloat targets.)
---
 compiler/rustc_codegen_llvm/src/llvm_util.rs | 4 +++-
 tests/run-make/target-cpu-native/foo.rs      | 8 ++++++++
 tests/run-make/target-cpu-native/rmake.rs    | 7 ++++++-
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_codegen_llvm/src/llvm_util.rs b/compiler/rustc_codegen_llvm/src/llvm_util.rs
index fbb582fe86018..85b515f2ef9cb 100644
--- a/compiler/rustc_codegen_llvm/src/llvm_util.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm_util.rs
@@ -702,7 +702,9 @@ pub(crate) fn global_llvm_features(sess: &Session, only_base_features: bool) ->
 
                 features_string
             };
-            features.extend(features_string.split(',').map(String::from));
+            if !features_string.is_empty() {
+                features.extend(features_string.split(',').map(String::from));
+            }
         }
         Some(_) | None => {}
     };
diff --git a/tests/run-make/target-cpu-native/foo.rs b/tests/run-make/target-cpu-native/foo.rs
index f328e4d9d04c3..5abcd25abc3f3 100644
--- a/tests/run-make/target-cpu-native/foo.rs
+++ b/tests/run-make/target-cpu-native/foo.rs
@@ -1 +1,9 @@
 fn main() {}
+
+// This forces explicit emission of a +neon target feature on targets
+// where it is implied by the target-cpu, like aarch64-apple-darwin.
+// This is a regression test for #153397.
+#[cfg(target_feature = "neon")]
+#[target_feature(enable = "neon")]
+#[unsafe(no_mangle)]
+pub fn with_neon() {}
diff --git a/tests/run-make/target-cpu-native/rmake.rs b/tests/run-make/target-cpu-native/rmake.rs
index 7b7974f309789..5791bf01bba2b 100644
--- a/tests/run-make/target-cpu-native/rmake.rs
+++ b/tests/run-make/target-cpu-native/rmake.rs
@@ -8,7 +8,12 @@
 use run_make_support::{run, rustc};
 
 fn main() {
-    let out = rustc().input("foo.rs").arg("-Ctarget-cpu=native").run().stderr_utf8();
+    let out = rustc()
+        .input("foo.rs")
+        .arg("-Ctarget-cpu=native")
+        .arg("-Zverify-llvm-ir")
+        .run()
+        .stderr_utf8();
     run("foo");
     // There should be zero warnings emitted - the bug would cause "unknown CPU `native`"
     // to be printed out.