Suppress debuginfo on naked function arguments

src/librustc_mir_build/build/mod.rs

@@ -10,6 +10,7 @@ use rustc_hir::lang_items;
 use rustc_hir::{GeneratorKind, HirIdMap, Node};
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_infer::infer::TyCtxtInferExt;
+use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::middle::region;
 use rustc_middle::mir::*;
 use rustc_middle::ty::subst::Subst;
@@ -797,12 +798,22 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         argument_scope: region::Scope,
         ast_body: &'tcx hir::Expr<'tcx>,
     ) -> BlockAnd<()> {
+        let tcx = self.hir.tcx();
+        let attrs = tcx.codegen_fn_attrs(fn_def_id);
+        let naked = attrs.flags.contains(CodegenFnAttrFlags::NAKED);
+
         // Allocate locals for the function arguments
         for &ArgInfo(ty, _, arg_opt, _) in arguments.iter() {
             let source_info =
                 SourceInfo::outermost(arg_opt.map_or(self.fn_span, |arg| arg.pat.span));
             let arg_local = self.local_decls.push(LocalDecl::with_source_info(ty, source_info));
 
+            // Emit function argument debuginfo only for non-naked functions.
+            // See: https://github.com/rust-lang/rust/issues/42779
+            if naked {
+                continue;
+            }
+
             // If this is a simple binding pattern, give debuginfo a nice name.
             if let Some(arg) = arg_opt {
                 if let Some(ident) = arg.pat.simple_ident() {
@@ -815,7 +826,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
         }
 
-        let tcx = self.hir.tcx();
         let tcx_hir = tcx.hir();
         let hir_typeck_results = self.hir.typeck_results();
 

src/test/codegen/naked-functions.rs

@@ -18,7 +18,7 @@ pub fn naked_empty() {
 // CHECK-NEXT: define void @naked_with_args(i{{[0-9]+( %0)?}})
 pub fn naked_with_args(a: isize) {
     // CHECK-NEXT: {{.+}}:
-    // CHECK-NEXT: %a = alloca i{{[0-9]+}}
+    // CHECK-NEXT: %_1 = alloca i{{[0-9]+}}
     &a; // keep variable in an alloca
     // CHECK: ret void
 }
@@ -39,7 +39,7 @@ pub fn naked_with_return() -> isize {
 #[naked]
 pub fn naked_with_args_and_return(a: isize) -> isize {
     // CHECK-NEXT: {{.+}}:
-    // CHECK-NEXT: %a = alloca i{{[0-9]+}}
+    // CHECK-NEXT: %_1 = alloca i{{[0-9]+}}
     &a; // keep variable in an alloca
     // CHECK: ret i{{[0-9]+}} %{{[0-9]+}}
     a

src/test/debuginfo/function-arguments-naked.rs

@@ -0,0 +1,40 @@
+// min-lldb-version: 310
+
+// We have to ignore android because of this issue:
+// https://github.com/rust-lang/rust/issues/74847
+// ignore-android
+
+// compile-flags:-g
+
+// === GDB TESTS ===================================================================================
+
+// gdb-command:run
+
+// gdb-command:info args
+// gdb-check:No arguments.
+// gdb-command:continue
+
+// === LLDB TESTS ==================================================================================
+
+// lldb-command:run
+
+// lldb-command:frame variable
+// lldbg-check:(unsigned long) = 111 (unsigned long) = 222
+// lldbr-check:(unsigned long) = 111 (unsigned long) = 222
+// lldb-command:continue
+
+
+#![feature(naked_functions)]
+#![feature(omit_gdb_pretty_printer_section)]
+#![omit_gdb_pretty_printer_section]
+
+fn main() {
+    naked(111, 222);
+}
+
+#[naked]
+fn naked(x: usize, y: usize) {
+    zzz(); // #break
+}
+
+fn zzz() { () }