On February 23, 2018 6:06:51 PM GMT+01:00, Jakub Jelinek <ja...@redhat.com>
wrote:
>Hi!
>
>ipa_vr_ggc_hash_traits::equal does
> return a->type == b->type && a->min == b->min && a->max == b->max;
>so it requires pointer identical type (5 value enum) and min/max,
>hopefully only INTEGER_CSTs. Honza complained on IRC that during
>firefox a lot of time is spent in this hash table, probably because
>the hash function was poor, it hashes any ranges with the same
>min/max values but different TREE_TYPE (p->min) the same.
>
>The following patch adjusts the hash method to match the equal
>method, bootstrapped/regtested on x86_64-linux and i686-linux,
>ok for trunk?
>
>In theory we could get bigger savings by e.g. using operand_equal_p
>on p->min and p->max instead of pointer comparison, but not really sure
>if the VRP code is prepared for that. E.g. VRP cares whether min
>or max are the minimum or maximum of the corresponding type, but if we
>ignore the type completely, it could be any other integral type.
That would certainly lead to issues.
>We'd use the same value_range memory struct for unsigned char [5, 255]
>range, where it is [5, +INF] and for int, where it is just [5, 255].
>Does LTO canonicalize INTEGER_TYPEs using type_hash_canon?
No. It unifies with its own logic and types are not registered with the canon
hash.
In any
>case,
>I think further optimizations should be postponed for GCC9.
OK.
Thanks,
Richard.
>2018-02-23 Jakub Jelinek <ja...@redhat.com>
>
> * ipa-prop.c (ipa_vr_ggc_hash_traits::hash): Hash p->min and
> p->max as pointers rather than using iterative_hash_expr.
>
>--- gcc/ipa-prop.c.jj 2018-01-03 10:19:54.617533871 +0100
>+++ gcc/ipa-prop.c 2018-02-23 14:43:08.983733102 +0100
>@@ -111,12 +111,13 @@ struct ipa_vr_ggc_hash_traits : public g
> typedef value_range *compare_type;
> static hashval_t
> hash (const value_range *p)
>- {
>- gcc_checking_assert (!p->equiv);
>- hashval_t t = (hashval_t) p->type;
>- t = iterative_hash_expr (p->min, t);
>- return iterative_hash_expr (p->max, t);
>- }
>+ {
>+ gcc_checking_assert (!p->equiv);
>+ inchash::hash hstate (p->type);
>+ hstate.add_ptr (p->min);
>+ hstate.add_ptr (p->max);
>+ return hstate.end ();
>+ }
> static bool
> equal (const value_range *a, const value_range *b)
> {
>
> Jakub
