gcov: Add -fprofile-info-section support

Register the profile information in the specified section instead of using a
constructor/destructor.  A pointer to the profile information generated by
-fprofile-arcs or -ftest-coverage is placed in the specified section for each
translation unit.  This option disables the profile information registration
through a constructor and it disables the profile information processing
through a destructor.

I am not sure how I can test this option.  One approach would be to assemble a
test file, then scan it and check that a .gcov_info section is present and no
__gcov_init() and __gcov_exit() calls are present.  Is there an example for
this in the test suite?

gcc/

	* common.opt (fprofile-info-section): New.
	* coverage.c (build_gcov_info_var_registration): New.
	(coverage_obj_init): Evaluate profile_info_section and use
	build_gcov_info_var_registration().
	* doc/invoke.texi (fprofile-info-section): Document.
	* opts.c (common_handle_option): Process fprofile-info-section
	option.

gcc/testsuite/ChangeLog:

	* gcc.dg/profile-info-section.c: New test.

1 files changed, 26 insertions, 2 deletions

diff --git a/gcc/coverage.c b/gcc/coverage.c
index 7711412..d299e48 100644
--- a/gcc/coverage.c
+++ b/gcc/coverage.c
@@ -1097,6 +1097,25 @@ build_gcov_exit_decl (void)
   cgraph_build_static_cdtor ('D', dtor, priority);
 }
 
+/* Generate the pointer to the gcov_info_var in a dedicated section.  */
+
+static void
+build_gcov_info_var_registration (tree gcov_info_type)
+{
+  tree var = build_decl (BUILTINS_LOCATION,
+			 VAR_DECL, NULL_TREE,
+			 build_pointer_type (gcov_info_type));
+  TREE_STATIC (var) = 1;
+  TREE_READONLY (var) = 1;
+  char name_buf[32];
+  ASM_GENERATE_INTERNAL_LABEL (name_buf, "LPBX", 2);
+  DECL_NAME (var) = get_identifier (name_buf);
+  get_section (profile_info_section, SECTION_UNNAMED, NULL);
+  set_decl_section_name (var, profile_info_section);
+  DECL_INITIAL (var) = build_fold_addr_expr (gcov_info_var);
+  varpool_node::finalize_decl (var);
+}
+
 /* Create the gcov_info types and object.  Generate the constructor
    function to call __gcov_init.  Does not generate the initializer
    for the object.  Returns TRUE if coverage data is being emitted.  */
@@ -1151,8 +1170,13 @@ coverage_obj_init (void)
   ASM_GENERATE_INTERNAL_LABEL (name_buf, "LPBX", 0);
   DECL_NAME (gcov_info_var) = get_identifier (name_buf);
 
-  build_init_ctor (gcov_info_type);
-  build_gcov_exit_decl ();
+  if (profile_info_section)
+    build_gcov_info_var_registration (gcov_info_type);
+  else
+    {
+      build_init_ctor (gcov_info_type);
+      build_gcov_exit_decl ();
+    }
 
   return true;
 }