add rust_dbg_extern_identity_TwoDoubles to prevent check-fast failure

src/rt/rust_builtin.cpp

@@ -866,6 +866,16 @@ rust_dbg_extern_identity_TwoU64s(TwoU64s u) {
     return u;
 }
 
+struct TwoDoubles {
+    double one;
+    double two;
+};
+
+extern "C" CDECL TwoDoubles
+rust_dbg_extern_identity_TwoDoubles(TwoDoubles u) {
+    return u;
+}
+
 extern "C" CDECL double
 rust_dbg_extern_identity_double(double u) {
     return u;

src/rt/rustrt.def.in

@@ -199,6 +199,7 @@ rust_opendir
 rust_dbg_extern_identity_u32
 rust_dbg_extern_identity_u64
 rust_dbg_extern_identity_TwoU64s
+rust_dbg_extern_identity_TwoDoubles
 rust_dbg_extern_identity_double
 rust_dbg_extern_identity_u8
 rust_get_rt_env

src/test/run-pass/issue-5754.rs

@@ -8,12 +8,13 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-struct S {
-    r: float
+struct TwoDoubles {
+    r: float,
+    i: float
 }
 
 extern "C" {
-    fn rust_dbg_extern_identity_double(arg1: S) -> float;
+    fn rust_dbg_extern_identity_TwoDoubles(arg1: TwoDoubles) -> TwoDoubles;
 }
 
 pub fn main() {}