| Message ID | CAHACq4o0k1RsGpn9XhjiPQ7qj+3JkPJLwW4xD4WPEkk6C0N+RQ@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
I've committed this patch.
-cary
2013-06-10 Cary Coutant <ccoutant@google.com>
gcc/
* dwarf2out.c (hash_external_ref): Use die_symbol or signature
for hash so that hash table traversal order is deterministic.
> Index: gcc/dwarf2out.c
> ===================================================================
> --- gcc/dwarf2out.c (revision 198260)
> +++ gcc/dwarf2out.c (working copy)
> @@ -7385,7 +7385,22 @@ static hashval_t
> hash_external_ref (const void *p)
> {
> const struct external_ref *r = (const struct external_ref *)p;
> - return htab_hash_pointer (r->type);
> + dw_die_ref die = r->type;
> + hashval_t h = 0;
> +
> + /* We can't use the address of the DIE for hashing, because
> + that will make the order of the stub DIEs non-deterministic. */
> + if (! die->comdat_type_p)
> + /* We have a symbol; use it to compute a hash. */
> + h = htab_hash_string (die->die_id.die_symbol);
> + else
> + {
> + /* We have a type signature; use a subset of the bits as the hash.
> + The 8-byte signature is at least as large as hashval_t. */
> + comdat_type_node_ref type_node = die->die_id.die_type_node;
> + memcpy (&h, type_node->signature, sizeof (h));
> + }
> + return h;
> }
>
> /* Compare external_refs. */
Index: gcc/dwarf2out.c =================================================================== --- gcc/dwarf2out.c (revision 198260) +++ gcc/dwarf2out.c (working copy) @@ -7385,7 +7385,22 @@ static hashval_t hash_external_ref (const void *p) { const struct external_ref *r = (const struct external_ref *)p; - return htab_hash_pointer (r->type); + dw_die_ref die = r->type; + hashval_t h = 0; + + /* We can't use the address of the DIE for hashing, because + that will make the order of the stub DIEs non-deterministic. */ + if (! die->comdat_type_p) + /* We have a symbol; use it to compute a hash. */ + h = htab_hash_string (die->die_id.die_symbol); + else + { + /* We have a type signature; use a subset of the bits as the hash. + The 8-byte signature is at least as large as hashval_t. */ + comdat_type_node_ref type_node = die->die_id.die_type_node; + memcpy (&h, type_node->signature, sizeof (h)); + } + return h; } /* Compare external_refs. */
Jason, would you like to take a look at this patch before I commit it? If I turn on -fdebug-types-section, I get a random failure in g++.dg/pch/system-2.C. This failure is being caused by non-deterministic order of the type stubs emitted by optimize_external_refs, because it's using the address of the DIE as a hash for the extern_map hash table. This patch makes the output order deterministic by using either the die_symbol (as a string) or the type signature for the hash value. Bootstrapped on x86_64 with no regressions. (I'm not planning to turn on -fdebug-types-section by default; I'm just trying to make sure the test suite is clean with it on so that I can turn it on in the google branches.) -cary 2013-04-24 Cary Coutant <ccoutant@google.com> gcc/ * dwarf2out.c (hash_external_ref): Use die_symbol or signature for hash so that hash table traversal order is deterministic.