[PATCH 1/3] attribs: Cache the gnu namespace

[Richard Sandiford]

Later patches add more calls to get_attribute_namespace.
For scoped attributes, this is a simple operation on tree pointers.
But for normal GNU attributes (the vast majority), it involves a
call to get_identifier ("gnu").  This patch caches the identifier
for speed.

Admittedly I'm just going off gut instinct here.  I'm happy to drop
the patch if this doesn't seem worth a new GC root.

Tested on aarch64-linux-gnu & x86_64-linux-gnu.  OK to install?

Richard

gcc/
        * Makefile.in (GTFILES): Add attribs.cc.
        * attribs.cc (gnu_namespace_cache): New variable.
        (get_gnu_namespace): New function.
        (lookup_attribute_spec): Use it instead of get_identifier ("gnu").
        (get_attribute_namespace, attribs_cc_tests): Likewise.
---
 gcc/Makefile.in |  3 ++-
 gcc/attribs.cc  | 19 +++++++++++++++++--
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index 29cec21c825..a128ff76c07 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -2812,7 +2812,8 @@ GTFILES = $(CPPLIB_H) $(srcdir)/input.h 
$(srcdir)/coretypes.h \
   $(srcdir)/symtab-thunks.h $(srcdir)/symtab-thunks.cc \
   $(srcdir)/symtab-clones.h \
   $(srcdir)/reload.h $(srcdir)/caller-save.cc $(srcdir)/symtab.cc \
-  $(srcdir)/alias.cc $(srcdir)/bitmap.cc $(srcdir)/cselib.cc 
$(srcdir)/cgraph.cc \
+  $(srcdir)/alias.cc $(srcdir)/attribs.cc \
+  $(srcdir)/bitmap.cc $(srcdir)/cselib.cc $(srcdir)/cgraph.cc \
   $(srcdir)/ipa-prop.cc $(srcdir)/ipa-cp.cc $(srcdir)/ipa-utils.h \
   $(srcdir)/ipa-param-manipulation.h $(srcdir)/ipa-sra.cc \
   $(srcdir)/ipa-modref.h $(srcdir)/ipa-modref.cc \
diff --git a/gcc/attribs.cc b/gcc/attribs.cc
index 6725fe78f2c..6c70110e350 100644
--- a/gcc/attribs.cc
+++ b/gcc/attribs.cc
@@ -102,6 +102,19 @@ static const struct attribute_spec 
*lookup_scoped_attribute_spec (const_tree,
 
 static bool attributes_initialized = false;
 
+/* Do not use directly; go through get_gnu_namespace instead.  */
+static GTY(()) tree gnu_namespace_cache;
+
+/* Return the IDENTIFIER_NODE for the gnu namespace.  */
+
+static tree
+get_gnu_namespace ()
+{
+  if (!gnu_namespace_cache)
+    gnu_namespace_cache = get_identifier ("gnu");
+  return gnu_namespace_cache;
+}
+
 /* Return base name of the attribute.  Ie '__attr__' is turned into 'attr'.
    To avoid need for copying, we simply return length of the string.  */
 
@@ -403,7 +416,7 @@ lookup_attribute_spec (const_tree name)
       name = TREE_VALUE (name);
     }
   else
-    ns = get_identifier ("gnu");
+    ns = get_gnu_namespace ();
   return lookup_scoped_attribute_spec (ns, name);
 }
 
@@ -420,7 +433,7 @@ get_attribute_namespace (const_tree attr)
 {
   if (cxx11_attribute_p (attr))
     return TREE_PURPOSE (TREE_PURPOSE (attr));
-  return get_identifier ("gnu");
+  return get_gnu_namespace ();
 }
 
 /* Check LAST_DECL and NODE of the same symbol for attributes that are
@@ -2689,3 +2702,5 @@ attribs_cc_tests ()
 } /* namespace selftest */
 
 #endif /* CHECKING_P */
+
+#include "gt-attribs.h"
-- 
2.25.1