[PATCH][GCC][AARCH64] Fix libstdc++ build failure after r271735

	gcc/ChangeLog
	* aarch64/aarch64.c (aarch64_post_cfi_startproc): Add
	cfun->is_thunk check.

From-SVN: r271780

gcc/ChangeLog

+2019-05-30  Sam Tebbs  <sam.tebbs@arm.com>
+
+	* aarch64/aarch64.c (aarch64_post_cfi_startproc): Add 
+	cfun->is_thunk check.
+
 2019-05-30  Jakub Jelinek  <jakub@redhat.com>
 
 	* tree-predcom.c (is_inv_store_elimination_chain): Fix a typo - lenght

gcc/config/aarch64/aarch64.c

@@ -15370,7 +15370,7 @@ aarch64_declare_function_name (FILE *stream, const char* name,
 void
 aarch64_post_cfi_startproc (FILE *f, tree ignored ATTRIBUTE_UNUSED)
 {
-  if (aarch64_return_address_signing_enabled ()
+  if (!cfun->is_thunk && aarch64_return_address_signing_enabled ()
       && aarch64_ra_sign_key == AARCH64_KEY_B)
 	asm_fprintf (f, "\t.cfi_b_key_frame\n");
 }