3 files changed, 19 insertions, 1 deletions
diff --git a/compiler/rustc_codegen_llvm/src/abi.rs b/compiler/rustc_codegen_llvm/src/abi.rs
index 009e7e2487b..043123fcab2 100644
--- a/compiler/rustc_codegen_llvm/src/abi.rs
+++ b/compiler/rustc_codegen_llvm/src/abi.rs
@@ -24,6 +24,7 @@ use crate::attributes::{self, llfn_attrs_from_instance};
 use crate::builder::Builder;
 use crate::context::CodegenCx;
 use crate::llvm::{self, Attribute, AttributePlace};
+use crate::llvm_util;
 use crate::type_::Type;
 use crate::type_of::LayoutLlvmExt;
 use crate::value::Value;
@@ -500,7 +501,16 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
                     }
                 }
                 PassMode::Indirect { attrs, meta_attrs: None, on_stack: false } => {
-                    apply(attrs);
+                    let i = apply(attrs);
+                    if cx.sess().opts.optimize != config::OptLevel::No
+                        && llvm_util::get_version() >= (21, 0, 0)
+                    {
+                        attributes::apply_to_llfn(
+                            llfn,
+                            llvm::AttributePlace::Argument(i),
+                            &[llvm::AttributeKind::DeadOnReturn.create_attr(cx.llcx)],
+                        );
+                    }
                 }
                 PassMode::Indirect { attrs, meta_attrs: Some(meta_attrs), on_stack } => {
                     assert!(!on_stack);
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 75d3d27f74e..ad3c3d5932e 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -249,6 +249,7 @@ pub(crate) enum AttributeKind {
     FnRetThunkExtern = 41,
     Writable = 42,
     DeadOnUnwind = 43,
+    DeadOnReturn = 44,
 }
 
 /// LLVMIntPredicate
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 588d867bbbf..cd4f80f808c 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -277,6 +277,7 @@ enum class LLVMRustAttributeKind {
   FnRetThunkExtern = 41,
   Writable = 42,
   DeadOnUnwind = 43,
+  DeadOnReturn = 44,
 };
 
 static Attribute::AttrKind fromRust(LLVMRustAttributeKind Kind) {
@@ -369,6 +370,12 @@ static Attribute::AttrKind fromRust(LLVMRustAttributeKind Kind) {
     return Attribute::Writable;
   case LLVMRustAttributeKind::DeadOnUnwind:
     return Attribute::DeadOnUnwind;
+  case LLVMRustAttributeKind::DeadOnReturn:
+#if LLVM_VERSION_GE(21, 0)
+    return Attribute::DeadOnReturn;
+#else
+    report_fatal_error("DeadOnReturn attribute requires LLVM 21 or later");
+#endif
   }
   report_fatal_error("bad LLVMRustAttributeKind");
 }