Re: [PATCH] Introduce no_profile_instrument_function attribute (PR gcov-profile/68025)

[Martin Liška <mliska at suse dot cz>]

On 07/27/2016 11:33 PM, Jeff Law wrote:
> On 07/27/2016 02:27 AM, Martin Liška wrote:
>> Hi.
>>
>> As mentioned in the PR gcov-profile/68025, there's a request not to instrument
>> some functions (e.g. a in linux kernel). Thus, I come with a new attribute no_profile_instrument_function
>> which skips any profiling instrumentation.
>>
>> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
> Conceptually fine.  I think you need an update to extensions.texi to document the new attribute.  With that missing bit added, this will be fine for the trunk.
> 
> jeff

Thanks for the review, attaching final version of the patch I've just installed.

Martin

>From aa758454a83da441e5679eaa5f37a00126eb3298 Mon Sep 17 00:00:00 2001
From: marxin <mliska@suse.cz>
Date: Tue, 26 Jul 2016 15:03:29 +0200
Subject: [PATCH] Introduce no_profile_instrument_function attribute

gcc/ChangeLog:

2016-07-26  Martin Liska  <mliska@suse.cz>

	PR gcov-profile/68025
	* tree-profile.c (tree_profiling): Respect
	no_profile_instrument_function attribute.
	* doc/extend.texi: Document no_profile_instrument_function
	attribute.

gcc/c-family/ChangeLog:

2016-07-26  Martin Liska  <mliska@suse.cz>

	PR gcov-profile/68025
	* c-common.c (handle_no_profile_instrument_function_attribute):

gcc/testsuite/ChangeLog:

2016-07-26  Martin Liska  <mliska@suse.cz>

	PR gcov-profile/68025
	* gcc.dg/no_profile_instrument_function-attr-1.c: New test.
---
 gcc/c-family/c-common.c                            | 21 ++++++++++++++++++++
 gcc/doc/extend.texi                                |  6 ++++++
 .../gcc.dg/no_profile_instrument_function-attr-1.c | 23 ++++++++++++++++++++++
 gcc/tree-profile.c                                 |  3 +++
 4 files changed, 53 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c

diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 1c5974a..35b5e5d 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -353,6 +353,8 @@ static tree handle_tls_model_attribute (tree *, tree, tree, int,
 					bool *);
 static tree handle_no_instrument_function_attribute (tree *, tree,
 						     tree, int, bool *);
+static tree handle_no_profile_instrument_function_attribute (tree *, tree,
+							     tree, int, bool *);
 static tree handle_malloc_attribute (tree *, tree, tree, int, bool *);
 static tree handle_returns_twice_attribute (tree *, tree, tree, int, bool *);
 static tree handle_no_limit_stack_attribute (tree *, tree, tree, int,
@@ -717,6 +719,9 @@ const struct attribute_spec c_common_attribute_table[] =
   { "no_instrument_function", 0, 0, true,  false, false,
 			      handle_no_instrument_function_attribute,
 			      false },
+  { "no_profile_instrument_function",  0, 0, true, false, false,
+			      handle_no_profile_instrument_function_attribute,
+			      false },
   { "malloc",                 0, 0, true,  false, false,
 			      handle_malloc_attribute, false },
   { "returns_twice",          0, 0, true,  false, false,
@@ -8293,6 +8298,22 @@ handle_no_instrument_function_attribute (tree *node, tree name,
   return NULL_TREE;
 }
 
+/* Handle a "no_profile_instrument_function" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_no_profile_instrument_function_attribute (tree *node, tree name, tree,
+						 int, bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) != FUNCTION_DECL)
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored", name);
+      *no_add_attrs = true;
+    }
+
+  return NULL_TREE;
+}
+
 /* Handle a "malloc" attribute; arguments as in
    struct attribute_spec.handler.  */
 
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index ad8898c..70636c1 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -2853,6 +2853,12 @@ If @option{-finstrument-functions} is given, profiling function calls are
 generated at entry and exit of most user-compiled functions.
 Functions with this attribute are not so instrumented.
 
+@item no_profile_instrument_function
+@cindex @code{no_profile_instrument_function} function attribute
+The @code{no_profile_instrument_function} attribute on functions is used
+to inform the compiler that it should not process any profile feedback based
+optimization code instrumentation.
+
 @item no_reorder
 @cindex @code{no_reorder} function attribute
 Do not reorder functions or variables marked @code{no_reorder}
diff --git a/gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c b/gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c
new file mode 100644
index 0000000..c93d171
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/no_profile_instrument_function-attr-1.c
@@ -0,0 +1,23 @@
+/* { dg-options "-O2 -fprofile-generate -fdump-tree-optimized" } */
+
+__attribute__ ((no_profile_instrument_function))
+int foo()
+{
+  return 0;
+}
+
+__attribute__ ((no_profile_instrument_function))
+int bar()
+{
+  return 1;
+}
+
+int main ()
+{
+  return foo ();
+}
+
+/* { dg-final { scan-tree-dump-times "__gcov0\\.main.* = PROF_edge_counter" 1 "optimized"} } */
+/* { dg-final { scan-tree-dump-times "__gcov_indirect_call_profiler_v2" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__gcov_time_profiler" 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times "__gcov_init" 1 "optimized" } } */
diff --git a/gcc/tree-profile.c b/gcc/tree-profile.c
index 1f3a726..39fe15f 100644
--- a/gcc/tree-profile.c
+++ b/gcc/tree-profile.c
@@ -524,6 +524,9 @@ tree_profiling (void)
       if (DECL_SOURCE_LOCATION (node->decl) == BUILTINS_LOCATION)
 	continue;
 
+      if (lookup_attribute ("no_profile_instrument_function",
+			    DECL_ATTRIBUTES (node->decl)))
+	continue;
       /* Do not instrument extern inline functions when testing coverage.
 	 While this is not perfectly consistent (early inlined extern inlines
 	 will get acocunted), testsuite expects that.  */
-- 
2.9.2