attribs: Cache the gnu namespace

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.

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.

2 files changed, 19 insertions, 3 deletions

diff --git a/gcc/Makefile.in b/gcc/Makefile.in
index b79421e..e154f7c 100644
--- a/gcc/Makefile.in
+++ b/gcc/Makefile.in
@@ -2816,7 +2816,8 @@ 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 8ad9b3b..95b0d0f 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
@@ -2692,3 +2705,5 @@ attribs_cc_tests ()
 } /* namespace selftest */
 
 #endif /* CHECKING_P */
+
+#include "gt-attribs.h"