2 files changed, 13 insertions, 3 deletions
diff --git a/compiler/rustc_session/src/errors.rs b/compiler/rustc_session/src/errors.rs
index 1ffee01b2f1..78940462b2c 100644
--- a/compiler/rustc_session/src/errors.rs
+++ b/compiler/rustc_session/src/errors.rs
@@ -115,6 +115,10 @@ pub struct CannotEnableCrtStaticLinux;
 pub struct SanitizerCfiRequiresLto;
 
 #[derive(Diagnostic)]
+#[diag(session_sanitizer_cfi_requires_single_codegen_unit)]
+pub struct SanitizerCfiRequiresSingleCodegenUnit;
+
+#[derive(Diagnostic)]
 #[diag(session_sanitizer_cfi_canonical_jump_tables_requires_cfi)]
 pub struct SanitizerCfiCanonicalJumpTablesRequiresCfi;
 
diff --git a/compiler/rustc_session/src/session.rs b/compiler/rustc_session/src/session.rs
index ac745d16161..b25a6299125 100644
--- a/compiler/rustc_session/src/session.rs
+++ b/compiler/rustc_session/src/session.rs
@@ -1619,13 +1619,19 @@ fn validate_commandline_args_with_session_available(sess: &Session) {
 
     // LLVM CFI requires LTO.
     if sess.is_sanitizer_cfi_enabled()
-        && !(sess.lto() == config::Lto::Fat
-            || sess.lto() == config::Lto::Thin
-            || sess.opts.cg.linker_plugin_lto.enabled())
+        && !(sess.lto() == config::Lto::Fat || sess.opts.cg.linker_plugin_lto.enabled())
     {
         sess.emit_err(errors::SanitizerCfiRequiresLto);
     }
 
+    // LLVM CFI using rustc LTO requires a single codegen unit.
+    if sess.is_sanitizer_cfi_enabled()
+        && sess.lto() == config::Lto::Fat
+        && !(sess.codegen_units().as_usize() == 1)
+    {
+        sess.emit_err(errors::SanitizerCfiRequiresSingleCodegenUnit);
+    }
+
     // LLVM CFI is incompatible with LLVM KCFI.
     if sess.is_sanitizer_cfi_enabled() && sess.is_sanitizer_kcfi_enabled() {
         sess.emit_err(errors::CannotMixAndMatchSanitizers {