Preserve callee cgraph edges when callgraph profiles sections are requested. (issue5101042)

[Sriraman Tallam]

Forgot to mention the changes:

	* cgraphbuild.c (remove_cgraph_callee_edges): Preserve callee edges if
	callgraph profiles are needed.
	* final.c (rest_of_handle_final): Rename .note.callgraph sections as
	.gnu.callgraph sections.
	* tree-optimize.c (gate_all_optimizations): Set
	cgraph_callee_edges_final_cleanup to true.
	(cgraph_callee_edges_final_cleanup): New global variable.

	* g++.dg/tree-prof/callgraph-profiles.C: New test.

On Thu, Sep 22, 2011 at 4:01 PM, Sriraman Tallam <tmsriram@google.com> wrote:
> This patch preserves cgraph callee edges till pass_final if callgraph
> edge profiles sections are requested.  It also renames callgraph edge
> profile sections to be .gnu.callgraph instead of .note.callgraph
>
>
> Index: cgraphbuild.c
> ===================================================================
> --- cgraphbuild.c       (revision 179098)
> +++ cgraphbuild.c       (working copy)
> @@ -697,10 +697,18 @@ struct gimple_opt_pass pass_rebuild_cgraph_edges =
>  }
>  };
>
> +/* Defined in tree-optimize.c  */
> +extern bool cgraph_callee_edges_final_cleanup;
>
>  static unsigned int
>  remove_cgraph_callee_edges (void)
>  {
> +  /* The -fcallgraph-profiles-sections flag needs the call-graph preserved
> +     till pass_final.  */
> +  if (cgraph_callee_edges_final_cleanup
> +      && flag_callgraph_profiles_sections)
> +      return 0;
> +
>   cgraph_node_remove_callees (cgraph_node (current_function_decl));
>   return 0;
>  }
> Index: final.c
> ===================================================================
> --- final.c     (revision 179098)
> +++ final.c     (working copy)
> @@ -4425,10 +4425,11 @@ rest_of_handle_final (void)
>      profiling information. */
>   if (flag_callgraph_profiles_sections
>       && flag_profile_use
> -      && cgraph_node (current_function_decl) != NULL)
> +      && cgraph_node (current_function_decl) != NULL
> +      && (cgraph_node (current_function_decl))->callees != NULL)
>     {
>       flags = SECTION_DEBUG;
> -      asprintf (&profile_fnname, ".note.callgraph.text.%s", fnname);
> +      asprintf (&profile_fnname, ".gnu.callgraph.text.%s", fnname);
>       switch_to_section (get_section (profile_fnname, flags, NULL));
>       fprintf (asm_out_file, "\t.string \"Function %s\"\n", fnname);
>       dump_cgraph_profiles ();
> Index: testsuite/g++.dg/tree-prof/callgraph-profiles.C
> ===================================================================
> --- testsuite/g++.dg/tree-prof/callgraph-profiles.C     (revision 0)
> +++ testsuite/g++.dg/tree-prof/callgraph-profiles.C     (revision 0)
> @@ -0,0 +1,29 @@
> +/* Verify if call-graph profile sections are created
> +   with -fcallgraph-profiles-sections. */
> +/* { dg-options "-O2 -fcallgraph-profiles-sections -ffunction-sections --save-temps" } */
> +
> +int __attribute__ ((noinline))
> +foo ()
> +{
> +  return 1;
> +}
> +
> +int __attribute__ ((noinline))
> +bar ()
> +{
> +  return 0;
> +}
> +
> +int main ()
> +{
> +  int sum;
> +  for (int i = 0; i< 1000; i++)
> +    {
> +      sum = foo () + bar();
> +    }
> +  return sum * bar ();
> +}
> +
> +/* { dg-final-use { scan-assembler "\.gnu\.callgraph\.text\.main" } } */
> +/* { dg-final-use { scan-assembler "\.string \"1000\"" } } */
> +/* { dg-final-use { cleanup-saved-temps } }  */
> Index: tree-optimize.c
> ===================================================================
> --- tree-optimize.c     (revision 179098)
> +++ tree-optimize.c     (working copy)
> @@ -48,11 +48,17 @@ along with GCC; see the file COPYING3.  If not see
>  #include "plugin.h"
>  #include "regset.h"    /* FIXME: For reg_obstack.  */
>
> +/* Decides if the cgraph callee edges are being cleaned up for the
> +   last time.  */
> +bool cgraph_callee_edges_final_cleanup = false;
> +
>  /* Gate: execute, or not, all of the non-trivial optimizations.  */
>
>  static bool
>  gate_all_optimizations (void)
>  {
> +  /* The cgraph callee edges can be cleaned up for the last time.  */
> +  cgraph_callee_edges_final_cleanup = true;
>   return (optimize >= 1
>          /* Don't bother doing anything if the program has errors.
>             We have to pass down the queue if we already went into SSA */
>
> --
> This patch is available for review at http://codereview.appspot.com/5101042
>