IPA ICF: add no_icf attribute.

* c-common.c (handle_noicf_attribute): New function.
	* doc/extend.texi (no_icf): Add new attribute description.
	* ipa-icf.c (sem_item_optimizer::merge_classes): Handle cases
	where the pass attempts to merge a function with no_icf attribute.
	* gcc.dg/ipa/ipa-icf-33.c: New test.

From-SVN: r219848

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2015-01-19  Martin Liska  <mliska@suse.cz>
+
+	* doc/extend.texi (no_icf): Add new attribute description.
+	* ipa-icf.c (sem_item_optimizer::merge_classes): Handle cases
+	where the pass attempts to merge a function with no_icf attribute.
+
 2015-01-19  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
 
 	PR target/64532

gcc/c-family/ChangeLog

@@ -1,3 +1,7 @@
+2015-01-19  Martin Liska  <mliska@suse.cz>
+
+	* c-common.c (handle_noicf_attribute): New function.
+
 2015-01-15  Thomas Schwinge  <thomas@codesourcery.com>
 	    Bernd Schmidt  <bernds@codesourcery.com>
 	    James Norris  <jnorris@codesourcery.com>

gcc/c-family/c-common.c

@@ -330,6 +330,7 @@ static tree handle_no_sanitize_undefined_attribute (tree *, tree, tree, int,
 static tree handle_stack_protect_attribute (tree *, tree, tree, int, bool *);
 static tree handle_noinline_attribute (tree *, tree, tree, int, bool *);
 static tree handle_noclone_attribute (tree *, tree, tree, int, bool *);
+static tree handle_noicf_attribute (tree *, tree, tree, int, bool *);
 static tree handle_leaf_attribute (tree *, tree, tree, int, bool *);
 static tree handle_always_inline_attribute (tree *, tree, tree, int,
 					    bool *);
@@ -664,6 +665,8 @@ const struct attribute_spec c_common_attribute_table[] =
 			      handle_noinline_attribute, false },
   { "noclone",                0, 0, true,  false, false,
 			      handle_noclone_attribute, false },
+  { "no_icf",                 0, 0, true,  false, false,
+			      handle_noicf_attribute, false },
   { "leaf",                   0, 0, true,  false, false,
 			      handle_leaf_attribute, false },
   { "always_inline",          0, 0, true,  false, false,
@@ -6853,6 +6856,24 @@ handle_noclone_attribute (tree *node, tree name,
   return NULL_TREE;
 }
 
+/* Handle a "no_icf" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_noicf_attribute (tree *node, tree name,
+			tree ARG_UNUSED (args),
+			int ARG_UNUSED (flags), 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 "always_inline" attribute; arguments as in
    struct attribute_spec.handler.  */
 

gcc/doc/extend.texi

@@ -2195,6 +2195,7 @@ attribute specification inside double parentheses.  The following
 attributes are currently defined for functions on all targets:
 @code{aligned}, @code{alloc_size}, @code{alloc_align}, @code{assume_aligned},
 @code{noreturn}, @code{returns_twice}, @code{noinline}, @code{noclone},
+@code{no_icf},
 @code{always_inline}, @code{flatten}, @code{pure}, @code{const},
 @code{nothrow}, @code{sentinel}, @code{format}, @code{format_arg},
 @code{no_instrument_function}, @code{no_split_stack},
@@ -3475,6 +3476,11 @@ cloning---a mechanism that produces specialized copies of functions
 and which is (currently) performed by interprocedural constant
 propagation.
 
+@item no_icf
+@cindex @code{no_icf} function attribute
+This function attribute prevents a functions from being merged with another
+semantically equivalent function.
+
 @item nonnull (@var{arg-index}, @dots{})
 @cindex @code{nonnull} function attribute
 The @code{nonnull} attribute specifies that some function parameters should

gcc/ipa-icf.c

@@ -2373,6 +2373,16 @@ sem_item_optimizer::merge_classes (unsigned int prev_class_count)
 			 source->asm_name (), alias->asm_name ());
 	      }
 
+	    if (lookup_attribute ("no_icf", DECL_ATTRIBUTES (alias->decl)))
+	      {
+	        if (dump_file)
+		  fprintf (dump_file,
+			   "Merge operation is skipped due to no_icf "
+			   "attribute.\n\n");
+
+		continue;
+	      }
+
 	    if (dump_file && (dump_flags & TDF_DETAILS))
 	      {
 		source->dump_to_file (dump_file);

gcc/testsuite/ChangeLog

@@ -1,3 +1,7 @@
+2015-01-19  Martin Liska  <mliska@suse.cz>
+
+	* gcc.dg/ipa/ipa-icf-33.c: New test.
+
 2015-01-19  Felix Yang  <felix.yang@huawei.com>
 	    Haijian Zhang  <z.zhanghaijian@huawei.com>
 

gcc/testsuite/gcc.dg/ipa/ipa-icf-33.c

@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+/* { dg-options "-O0 -fipa-icf -fdump-ipa-icf"  } */
+
+#include <stdio.h>
+
+static int
+__attribute__ ((no_icf))
+foo()
+{
+  return 2;
+}
+
+static int
+__attribute__ ((no_icf))
+bar()
+{
+  return 2;
+}
+
+int main()
+{
+  return foo() - bar();
+}
+
+/* { dg-final { scan-ipa-dump "Equal symbols: 1" "icf"  } } */
+/* { dg-final { scan-ipa-dump "Equal symbols: 1" "icf"  } } */
+/* { dg-final { cleanup-ipa-dump "icf" } } */