[metadata] Avoid realloc and memcpy when >1 gparams on generics (#66458)

* [metadata] Avoid realloc and memcpy when >1 gparams on generics

* Read the first gparam row again at the beginning of the second pass

diff --git a/src/mono/mono/metadata/metadata.c b/src/mono/mono/metadata/metadata.c
index 440414e..a9d15e5 100644 (file)
--- a/src/mono/mono/metadata/metadata.c
+++ b/src/mono/mono/metadata/metadata.c
@@ -7205,10 +7205,21 @@ mono_metadata_load_generic_params (MonoImage *image, guint32 token, MonoGenericC
                else
                        container->owner.klass = (MonoClass*)real_owner;
        }
+       /* first pass over the gparam table - just count how many params we own */
+       uint32_t type_argc = 0;
+       uint32_t i2 = i;
+       do {
+               type_argc++;
+               if (++i2 > mono_metadata_table_num_rows (image, MONO_TABLE_GENERICPARAM))
+                       break;
+               mono_metadata_decode_row (tdef, i2 - 1, cols, MONO_GENERICPARAM_SIZE);
+       } while (cols [MONO_GENERICPARAM_OWNER] == owner);
+       params = (MonoGenericParamFull *)mono_image_alloc0 (image, sizeof (MonoGenericParamFull) * type_argc);
+
+       /* second pass, fill in the gparam data */
+       mono_metadata_decode_row (tdef, i - 1, cols, MONO_GENERICPARAM_SIZE);
        do {
                n++;
-               params = (MonoGenericParamFull *)g_realloc (params, sizeof (MonoGenericParamFull) * n);
-               memset (&params [n - 1], 0, sizeof (MonoGenericParamFull));
                params [n - 1].owner = container;
                params [n - 1].num = cols [MONO_GENERICPARAM_NUMBER];
                params [n - 1].info.token = i | MONO_TOKEN_GENERIC_PARAM;
@@ -7216,16 +7227,13 @@ mono_metadata_load_generic_params (MonoImage *image, guint32 token, MonoGenericC
                params [n - 1].info.name = mono_metadata_string_heap (image, cols [MONO_GENERICPARAM_NAME]);
                if (params [n - 1].num != n - 1)
                        g_warning ("GenericParam table unsorted or hole in generic param sequence: token %d", i);
-               /* FIXME: metadata-update */
-               if (++i > table_info_get_rows (tdef))
+               if (++i > mono_metadata_table_num_rows (image, MONO_TABLE_GENERICPARAM))
                        break;
                mono_metadata_decode_row (tdef, i - 1, cols, MONO_GENERICPARAM_SIZE);
        } while (cols [MONO_GENERICPARAM_OWNER] == owner);
 
-       container->type_argc = n;
-       container->type_params = (MonoGenericParamFull *)mono_image_alloc0 (image, sizeof (MonoGenericParamFull) * n);
-       memcpy (container->type_params, params, sizeof (MonoGenericParamFull) * n);
-       g_free (params);
+       container->type_argc = type_argc;
+       container->type_params = params;
        container->parent = parent_container;
 
        if (is_method)