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Re: whereis PLUGIN_REGISTER_GGC_CACHES? how to migrate it for GCC v6.x?

在 2017年07月10日 22:16, David Malcolm 写道:
On Sat, 2017-07-08 at 15:50 +0800, Leslie Zhai wrote:
Hi GCC developers,

There was


pseudo-events for register_callback in GCC v4.x, but how to migrate
for GCC v6.x? there is no  PLUGIN_REGISTER_GGC_CACHES deprecated log
ChangeLog-201X nor git log plugin.h... please give me some hint,
a lot!
Trevor [CCed] removed it 2014-12-10 in r218558
(eb06b2519a361b7784b1807115fcb3dea0226035) in the commit:
"remove gengtype support for param_is use_param, if_marked and splay
tree allocators"

The patch was here:

where he talks about plugin migration.
Some plugins may need to add extra GGC root tables, e.g. to handle their own @code{GTY}-ed data. This can be done with the @code{PLUGIN_REGISTER_GGC_ROOTS} pseudo-event with a null callback and the extra root table (of type @code{struct
-ggc_root_tab*}) as @code{user_data}.  Plugins that want to use the
-@code{if_marked} hash table option can add the extra GGC cache tables generated -by @code{gengtype} using the @code{PLUGIN_REGISTER_GGC_CACHES} pseudo-event with -a null callback and the extra cache table (of type @code{struct ggc_cache_tab*})
-as @code{user_data}.  Running the @code{gengtype -p @var{source-dir}
-@var{file-list} @var{plugin*.c} ...} utility generates these extra root tables.
+ggc_root_tab*}) as @code{user_data}.  Running the
+ @code{gengtype -p @var{source-dir} @var{file-list} @var{plugin*.c} ...}
+utility generates these extra root tables.

After diff gcc-6.3.0/gcc/testsuite/gcc.dg/plugin and gcc-4.8.0/gcc/testsuite/gcc.dg/plugin
then migrate to GCC v6.x like this:

// Register our garbage collector roots.
#if GCC_MAJOR < 6
  register_callback(plugin_name, PLUGIN_REGISTER_GGC_CACHES, NULL,
  register_callback(plugin_name, PLUGIN_REGISTER_GGC_ROOTS, NULL,
                    const_cast<ggc_cache_tab *>(gt_ggc_rc__gt_cache_h));

and Trevor talks more about GTY((if_marked(XXX), param_is(XXX))) htab_t migrate to GTY((cache)) hash_table<MyHasher> such as:

#if (GCC_MAJOR < 6)
// FIXME: gengtype not support macro?
static GTY((if_marked("tree2int_marked_p"), param_is(struct tree2int)))
    htab_t intCache;
struct intCacheHasher : ggc_cache_ptr_hash<tree2int> {
  static inline hashval_t hash(tree2int *t2i) {
    return tree_map_base_hash(&t2i->base);

  static inline bool equal(tree2int *a, tree2int *b) {
    return a->base.from == b->base.from;
static GTY((cache))
    hash_table<intCacheHasher> *intCache;

But I have no idea why gengtype does not support macro? it just ignored #if (GCC_MAJOR < 6) still parse GTY((if_marked(XXX), param_is(XXX))) htab_t but not GTY((cache)) hash_table<MyHasher>... please give me some hint, thanks a lot!

Hope this is helpful

Leslie Zhai - a LLVM developer

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