For a specific testcase a lot of compile-time is spent in re-hashing
hashtable elements upon expansion. The following records the hash
in the hash element. This speeds up compilation by 20%.
There's probably module-related uses that need to be adjusted.
Bootstrap failed (guess I was expecting this), but still I think this
is a good idea - maybe somebody can pick it up. Possibly instead
of having a single global hash table having one per ID would be
better. The hashtable also keeps things GC-live ('args' for example).
gcc/cp/
* cp-tree.h (spec_entry::hash): New member.
* pt.cc (spec_hasher::hash): Return the elements recorded hash.
(lookup_template_class): Record the hash in the element.
---
gcc/cp/cp-tree.h | 1 +
gcc/cp/pt.cc | 6 +++---
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index c5d02567cb4..56345214d8f 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -5843,6 +5843,7 @@ struct GTY((for_user)) spec_entry
tree tmpl; /* The general template this is a specialization of. */
tree args; /* The args for this (maybe-partial) specialization. */
tree spec; /* The specialization itself. */
+ hashval_t hash;
};
/* in class.cc */
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 2c8b0d8609d..11f84133fa7 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -1739,7 +1739,7 @@ spec_hasher::hash (tree tmpl, tree args)
hashval_t
spec_hasher::hash (spec_entry *e)
{
- return spec_hasher::hash (e->tmpl, e->args);
+ return e->hash;
}
/* Recursively calculate a hash value for a template argument ARG, for use
@@ -10234,7 +10234,7 @@ lookup_template_class (tree d1, tree arglist, tree
in_decl, tree context,
elt.tmpl = gen_tmpl;
elt.args = arglist;
elt.spec = NULL_TREE;
- hash = spec_hasher::hash (&elt);
+ hash = elt.hash = spec_hasher::hash (gen_tmpl, arglist);
entry = type_specializations->find_with_hash (&elt, hash);
if (entry)
@@ -10519,7 +10519,7 @@ lookup_template_class (tree d1, tree arglist, tree
in_decl, tree context,
use it for hash table lookup. */
elt.tmpl = found;
elt.args = arglist = INNERMOST_TEMPLATE_ARGS (arglist);
- hash = spec_hasher::hash (&elt);
+ hash = elt.hash = spec_hasher::hash (found, arglist);
}
}
--
2.43.0
