FWIW I think that most of the speedup is due to inlining
lookup_attribute(). I got almost the same by applying only the attached
very simple patch, since strlen() was called too often (according to the
profile at [1]). I used the always_inline attribute to avoid using a
macro.
I was going to send it together with some other changes I'm trying and
after proper measurements. Anyway, better late than ever. Thanks to
Christophe Jaillet (CC'd) for pointing it to me.
Thanks,
Dimitris
[1] http://gcc.gnu.org/wiki/OptimisingGCC
On Tue, 21 Jun 2011, Richard Guenther wrote:
On Tue, Jun 21, 2011 at 12:17 PM, Nicola Pero
<nicola.p...@meta-innovation.com> wrote:
This patch speeds up the C/C++/ObjC/ObjC++ compiler a little bit by optimizing
lookup_attribute() and is_attribute_p(). The main change is that these
functions
are now inline.
I don't think this is a good idea.
Can you explain why ? You never do in your response :-)
I'm guessing it's because you think the inline functions are too big and that's
counter-productive ?
Yes.
For this case I'd factor out the NULL attribute list check into an
inline function and keeping the non-NULL attribute list pieces out-of-line.
Ok ... so is this what you'd like - the common, hot case in the inline function,
and the less common, cold case in the out-of-line one ? :-)
Right.
That makes sense - I'll try that out tonight (it takes a few hours to run all
the benchmarks). ;-)
Thanks.
Does it work for all languages? And yes, I agree it would be nice to
canonicalize to the form without _s even in the attribute lists itself.
Or go one step further - do not store an identifier but an enum as we
in fact only ever insert known attributes into the list (which should
be a VEC instead, possibly even sorted to allow binary search).
Sure ... one step at a time. :-)
Of course ;)
Richard.
Thanks
--- gcc-4.6.0.orig/gcc/tree.c 2011-03-14 14:20:48.000000000 +0200
+++ gcc-4.6.0-mine/gcc/tree.c 2011-06-21 12:57:00.000000000 +0300
@@ -5230,10 +5230,9 @@ is_attribute_p (const char *attr, const_
be passed back in if further occurrences are wanted. */
tree
-lookup_attribute (const char *attr_name, tree list)
+lookup_attribute_len (const char *attr_name, size_t attr_len, tree list)
{
tree l;
- size_t attr_len = strlen (attr_name);
for (l = list; l; l = TREE_CHAIN (l))
{
--- gcc-4.6.0.orig/gcc/tree.h 2011-03-12 00:38:58.000000000 +0200
+++ gcc-4.6.0-mine/gcc/tree.h 2011-06-21 13:13:02.000000000 +0300
@@ -4369,7 +4369,16 @@ extern int is_attribute_p (const char *,
/* Given an attribute name and a list of attributes, return the list element
of the attribute or NULL_TREE if not found. */
-extern tree lookup_attribute (const char *, tree);
+extern tree lookup_attribute_len (const char *, size_t, tree);
+
+/* implemented as inline so that the compiler optimises away the strlen() for
+ known strings*/
+static __attribute__((__always_inline__)) tree
+lookup_attribute (const char *attr_name, tree list)
+{
+ return lookup_attribute_len(attr_name, strlen (attr_name), list);
+}
+
/* Remove any instances of attribute ATTR_NAME in LIST and return the
modified list. */
