Auto merge of #124813 - maurer:llvm-aarch64-fn32, r=nikic

Adjust 64-bit ARM data layouts for LLVM update

LLVM has updated data layouts to specify `Fn32` on 64-bit ARM to avoid C++ accidentally underaligning functions when trying to comply with member function ABIs.

This should only affect Rust in cases where we had a similar bug (I don't believe we have one), but our data layout must match to generate code.

As a compatibility adaptatation, if LLVM is not version 19 yet, `Fn32` gets voided from the data layout.

See llvm/llvm-project#90415

`@rustbot` label: +llvm-main
cc `@krasimirgg`
r? `@durin42`

Author: bors

compiler/rustc_codegen_llvm/src/context.rs

@@ -133,6 +133,15 @@ pub unsafe fn create_module<'ll>(
         }
     }
 
+    if llvm_version < (19, 0, 0) {
+        if sess.target.arch == "aarch64" || sess.target.arch.starts_with("arm64") {
+            // LLVM 19 sets -Fn32 in its data layout string for 64-bit ARM
+            // Earlier LLVMs leave this default, so remove it.
+            // See https://github.com/llvm/llvm-project/pull/90702
+            target_data_layout = target_data_layout.replace("-Fn32", "");
+        }
+    }
+
     // Ensure the data-layout values hardcoded remain the defaults.
     {
         let tm = crate::back::write::create_informational_target_machine(tcx.sess);

compiler/rustc_target/src/spec/targets/aarch64_apple_darwin.rs

@@ -22,7 +22,7 @@ pub fn target() -> Target {
             std: None,
         },
         pointer_width: 64,
-        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: arch.target_arch(),
         options: TargetOptions {
             mcount: "\u{1}mcount".into(),

compiler/rustc_target/src/spec/targets/aarch64_apple_ios.rs

@@ -19,7 +19,7 @@ pub fn target() -> Target {
             std: None,
         },
         pointer_width: 64,
-        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: arch.target_arch(),
         options: TargetOptions {
             features: "+neon,+fp-armv8,+apple-a7".into(),

compiler/rustc_target/src/spec/targets/aarch64_apple_ios_macabi.rs

@@ -15,7 +15,7 @@ pub fn target() -> Target {
             std: None,
         },
         pointer_width: 64,
-        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: arch.target_arch(),
         options: TargetOptions {
             features: "+neon,+fp-armv8,+apple-a12".into(),

compiler/rustc_target/src/spec/targets/aarch64_apple_ios_sim.rs

@@ -19,7 +19,7 @@ pub fn target() -> Target {
             std: None,
         },
         pointer_width: 64,
-        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: arch.target_arch(),
         options: TargetOptions {
             features: "+neon,+fp-armv8,+apple-a7".into(),

compiler/rustc_target/src/spec/targets/aarch64_apple_tvos.rs

@@ -12,7 +12,7 @@ pub fn target() -> Target {
             std: None,
         },
         pointer_width: 64,
-        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: arch.target_arch(),
         options: TargetOptions {
             features: "+neon,+fp-armv8,+apple-a7".into(),

compiler/rustc_target/src/spec/targets/aarch64_apple_tvos_sim.rs

@@ -12,7 +12,7 @@ pub fn target() -> Target {
             std: None,
         },
         pointer_width: 64,
-        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: arch.target_arch(),
         options: TargetOptions {
             features: "+neon,+fp-armv8,+apple-a7".into(),

compiler/rustc_target/src/spec/targets/aarch64_apple_visionos.rs

@@ -15,7 +15,7 @@ pub fn target() -> Target {
             std: Some(false),
         },
         pointer_width: 64,
-        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: arch.target_arch(),
         options: TargetOptions {
             features: "+neon,+fp-armv8,+apple-a16".into(),

compiler/rustc_target/src/spec/targets/aarch64_apple_visionos_sim.rs

@@ -15,7 +15,7 @@ pub fn target() -> Target {
             std: Some(false),
         },
         pointer_width: 64,
-        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: arch.target_arch(),
         options: TargetOptions {
             features: "+neon,+fp-armv8,+apple-a16".into(),

compiler/rustc_target/src/spec/targets/aarch64_apple_watchos.rs

@@ -12,7 +12,7 @@ pub fn target() -> Target {
             std: None,
         },
         pointer_width: 64,
-        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128".into(),
+        data_layout: "e-m:o-i64:64-i128:128-n32:64-S128-Fn32".into(),
         arch: "aarch64".into(),
         options: TargetOptions {
             features: "+v8a,+neon,+fp-armv8,+apple-a7".into(),