Check AArch64 branch-protection earlier in the pipeline.

As suggested in #93516.

2 files changed, 12 insertions, 4 deletions

diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index 8cb9e1a6f1a..fd7dabf75ef 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -116,6 +116,10 @@ pub struct StackProtectorNotSupportedForTarget<'a> {
 }
 
 #[derive(Diagnostic)]
+#[diag(session_branch_protection_requires_aarch64)]
+pub(crate) struct BranchProtectionRequiresAArch64;
+
+#[derive(Diagnostic)]
 #[diag(session_split_debuginfo_unstable_platform)]
 pub struct SplitDebugInfoUnstablePlatform {
     pub debuginfo: SplitDebuginfo,
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index e99e460913e..ce4a2e3d82d 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -3,10 +3,10 @@ use crate::code_stats::CodeStats;
 pub use crate::code_stats::{DataTypeKind, FieldInfo, SizeKind, VariantInfo};
 use crate::config::{self, CrateType, InstrumentCoverage, OptLevel, OutputType, SwitchWithOptPath};
 use crate::errors::{
-    CannotEnableCrtStaticLinux, CannotMixAndMatchSanitizers, LinkerPluginToWindowsNotSupported,
-    NotCircumventFeature, ProfileSampleUseFileDoesNotExist, ProfileUseFileDoesNotExist,
-    SanitizerCfiEnabled, SanitizerNotSupported, SanitizersNotSupported, SkippingConstChecks,
-    SplitDebugInfoUnstablePlatform, StackProtectorNotSupportedForTarget,
+    BranchProtectionRequiresAArch64, CannotEnableCrtStaticLinux, CannotMixAndMatchSanitizers,
+    LinkerPluginToWindowsNotSupported, NotCircumventFeature, ProfileSampleUseFileDoesNotExist,
+    ProfileUseFileDoesNotExist, SanitizerCfiEnabled, SanitizerNotSupported, SanitizersNotSupported,
+    SkippingConstChecks, SplitDebugInfoUnstablePlatform, StackProtectorNotSupportedForTarget,
     TargetRequiresUnwindTables, UnleashedFeatureHelp, UnstableVirtualFunctionElimination,
     UnsupportedDwarfVersion,
 };
@@ -1542,6 +1542,10 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
         }
     }
 
+    if sess.opts.unstable_opts.branch_protection.is_some() && sess.target.arch != "aarch64" {
+        sess.emit_err(BranchProtectionRequiresAArch64);
+    }
+
     if let Some(dwarf_version) = sess.opts.unstable_opts.dwarf_version {
         if dwarf_version > 5 {
             sess.emit_err(UnsupportedDwarfVersion { dwarf_version });