fixup! WIP: Add support for function attributes

Add support for returns_twice attribute in libgccjit

Author: GuillaumeGomez

gcc/jit/jit-playback.cc

@@ -529,6 +529,8 @@ const char* fn_attribute_to_string(gcc_jit_fn_attribute attr)
       return "visibility";
     case GCC_JIT_FN_ATTRIBUTE_COLD:
       return "cold";
+    case GCC_JIT_FN_ATTRIBUTE_RETURNS_TWICE:
+      return "returns_twice";
   }
   return NULL;
 }
@@ -667,6 +669,9 @@ new_function (location *loc,
       TREE_USED (fndecl) = 1;
       DECL_PRESERVE_P (fndecl) = 1;
     }
+    /* See handle_returns_twice_attribute in gcc/c-family/c-attribs.cc. */
+    else if (attr == GCC_JIT_FN_ATTRIBUTE_RETURNS_TWICE)
+      DECL_IS_RETURNS_TWICE (fndecl) = 1;
 
     const char* attribute = fn_attribute_to_string (attr);
     if (attribute)

gcc/jit/libgccjit.h

@@ -2104,6 +2104,7 @@ enum gcc_jit_fn_attribute
   GCC_JIT_FN_ATTRIBUTE_USED,
   GCC_JIT_FN_ATTRIBUTE_VISIBILITY,
   GCC_JIT_FN_ATTRIBUTE_COLD,
+  GCC_JIT_FN_ATTRIBUTE_RETURNS_TWICE,
 };
 
 /* Add an attribute to a function.  */