* [patch] Fix non-deterministic output order for type stubs in DWARF output
@ 2013-04-25 8:04 Cary Coutant
2013-06-10 23:50 ` Cary Coutant
0 siblings, 1 reply; 2+ messages in thread
From: Cary Coutant @ 2013-04-25 8:04 UTC (permalink / raw)
To: Jason Merrill, gcc-patches
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.
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. */
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [patch] Fix non-deterministic output order for type stubs in DWARF output
2013-04-25 8:04 [patch] Fix non-deterministic output order for type stubs in DWARF output Cary Coutant
@ 2013-06-10 23:50 ` Cary Coutant
0 siblings, 0 replies; 2+ messages in thread
From: Cary Coutant @ 2013-06-10 23:50 UTC (permalink / raw)
To: Jason Merrill, gcc-patches
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. */
^ permalink raw reply [flat|nested] 2+ messages in thread
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