remove custom va_end implementation in the LLVM backend

it should use the fallback body instead

Author: folkertdev

compiler/rustc_codegen_ssa/src/mir/intrinsic.rs

@@ -148,8 +148,9 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 return Ok(());
             }
 
+            // va_end uses the fallback body (a no-op).
             sym::va_start => bx.va_start(args[0].immediate()),
-            sym::va_end => bx.va_end(args[0].immediate()),
+
             sym::size_of_val => {
                 let tp_ty = fn_args.type_at(0);
                 let (_, meta) = args[0].val.pointer_parts();

tests/codegen-llvm/c-variadic-va-end.rs

@@ -0,0 +1,19 @@
+//@ add-minicore
+//@ compile-flags: -Copt-level=3
+#![feature(c_variadic)]
+#![crate_type = "lib"]
+
+unsafe extern "C" {
+    fn g(v: *mut u8);
+}
+
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn f(mut args: ...) {
+    // CHECK: call void @llvm.va_start
+    unsafe { g(&raw mut args as *mut u8) }
+    // We expect one call to the LLVM va_end from our desugaring of `...`. The `Drop` implementation
+    // should only call the rust va_end intrinsic, which is a no-op.
+    //
+    // CHECK: call void @llvm.va_end
+    // CHECK-NOT: call void @llvm.va_end
+}