x86: Speed up target attribute handling by using a cache

The target attribute handling is very expensive and for the common case
from x86intrin.h where many functions get implicitly the same target
attribute, we can speed up compilation a lot by caching it.

The following patches both create a single entry cache, where they cache
for a particular target attribute argument list the resulting
DECL_FUNCTION_SPECIFIC_TARGET and DECL_FUNCTION_SPECIFIC_OPTIMIZATION
values from ix86_valid_target_attribute_p and use the cache if the
args are the same as last time and we start either from NULL values
of those, or from the recorded values for those from last time.

Compiling a simple:
 #include <x86intrin.h>

 int i;
testcase with ./cc1 -quiet -O2 -isystem include/ test.c
takes on my WS without the patches ~0.392s and with either of the
patches ~0.182s, i.e. roughly half the time as before.
For ./cc1plus -quiet -O2 -isystem include/ test.c
it is slightly worse, the speed up is from ~0.613s to ~0.403s.

The difference between the 2 patches is that the first one uses copy_list
while the second one uses a vec, so I think the second one has the advantage
of creating less GC garbage.
I've verified both patches achieve the same content of those
DECL_FUNCTION_SPECIFIC_TARGET and DECL_FUNCTION_SPECIFIC_OPTIMIZATION
nodes as before on x86intrin.h by doing debug_tree on those and comparing
the stderr from without these patches to with these patches.

2021-12-03  Jakub Jelinek  <jakub@redhat.com>

	* attribs.h (simple_cst_list_equal): Declare.
	* attribs.c (simple_cst_list_equal): No longer static.
	* config/i386/i386-options.c (target_attribute_cache): New variable.
	(ix86_valid_target_attribute_p): Cache DECL_FUNCTION_SPECIFIC_TARGET
	and DECL_FUNCTION_SPECIFIC_OPTIMIZATION based on args.

diff --git a/gcc/attribs.c b/gcc/attribs.c
index c252f5af07b4296630f833a5e4bc8bf60244e049..32c941506f4069acb06a7a6143e08b886938e367 100644 (file)
--- a/gcc/attribs.c
+++ b/gcc/attribs.c
@@ -1285,7 +1285,7 @@ cmp_attrib_identifiers (const_tree attr1, const_tree attr2)
 /* Compare two constructor-element-type constants.  Return 1 if the lists
    are known to be equal; otherwise return 0.  */
 
-static bool
+bool
 simple_cst_list_equal (const_tree l1, const_tree l2)
 {
   while (l1 != NULL_TREE && l2 != NULL_TREE)

diff --git a/gcc/attribs.h b/gcc/attribs.h
index 73f0ccc24b81faf30c6241fa8d9568c045913194..f5899d83c0be80cfc3806d9b4d6ced537b102494 100644 (file)
--- a/gcc/attribs.h
+++ b/gcc/attribs.h
@@ -60,6 +60,7 @@ extern tree build_type_attribute_variant (tree, tree);
 extern tree build_decl_attribute_variant (tree, tree);
 extern tree build_type_attribute_qual_variant (tree, tree, int);
 
+extern bool simple_cst_list_equal (const_tree, const_tree);
 extern bool attribute_value_equal (const_tree, const_tree);
 
 /* Return 0 if the attributes for two types are incompatible, 1 if they

diff --git a/gcc/config/i386/i386-options.c b/gcc/config/i386/i386-options.c
index a4da8331b8b7fc638bb05ca54d41e326cfecaffd..f971e03abad5589b38b79637ca923baa3ff106b1 100644 (file)
--- a/gcc/config/i386/i386-options.c
+++ b/gcc/config/i386/i386-options.c
@@ -1403,6 +1403,8 @@ ix86_valid_target_attribute_tree (tree fndecl, tree args,
   return t;
 }
 
+static GTY(()) tree target_attribute_cache[3];
+
 /* Hook to validate attribute((target("string"))).  */
 
 bool
@@ -1423,6 +1425,19 @@ ix86_valid_target_attribute_p (tree fndecl,
       && strcmp (TREE_STRING_POINTER (TREE_VALUE (args)), "default") == 0)
     return true;
 
+  if ((DECL_FUNCTION_SPECIFIC_TARGET (fndecl) == target_attribute_cache[1]
+       || DECL_FUNCTION_SPECIFIC_TARGET (fndecl) == NULL_TREE)
+      && (DECL_FUNCTION_SPECIFIC_OPTIMIZATION (fndecl)
+         == target_attribute_cache[2]
+         || DECL_FUNCTION_SPECIFIC_OPTIMIZATION (fndecl) == NULL_TREE)
+      && simple_cst_list_equal (args, target_attribute_cache[0]))
+    {
+      DECL_FUNCTION_SPECIFIC_TARGET (fndecl) = target_attribute_cache[1];
+      DECL_FUNCTION_SPECIFIC_OPTIMIZATION (fndecl)
+       = target_attribute_cache[2];
+      return true;
+    }
+
   tree old_optimize = build_optimization_node (&global_options,
                                               &global_options_set);
 
@@ -1459,8 +1474,17 @@ ix86_valid_target_attribute_p (tree fndecl,
   if (new_target == error_mark_node)
     ret = false;
 
-  else if (fndecl && new_target)
+  else if (new_target)
     {
+      if (DECL_FUNCTION_SPECIFIC_TARGET (fndecl) == NULL_TREE
+         && DECL_FUNCTION_SPECIFIC_OPTIMIZATION (fndecl) == NULL_TREE)
+       {
+         target_attribute_cache[0] = copy_list (args);
+         target_attribute_cache[1] = new_target;
+         target_attribute_cache[2]
+           = old_optimize != new_optimize ? new_optimize : NULL_TREE;
+       }
+
       DECL_FUNCTION_SPECIFIC_TARGET (fndecl) = new_target;
 
       if (old_optimize != new_optimize)