[Bug optimization/15345] New: unreferenced nested inline functions not optimized away

[Bug optimization/15345] New: unreferenced nested inline functions not optimized away

[dank at kegel dot com]

On gcc-3.4.0, unreferenced nested inline functions are not
optimized away at -O0 or -O1.  This is a regression from gcc-2.95.x and gcc-3.2.2.
This breaks building glibc-2.3.2 for sparc64 (see
http://sources.redhat.com/ml/libc-alpha/2004-05/msg00066.html)
No idea why it doesn't break other architectures.

Here's a small test case:

void f(void)
{
        inline int g(void) {
            extern int should_be_optimized_away(void);
            return should_be_optimized_away();
        }
}

Compile with -S, then examine the .s file; you'll
see a reference to should_be_optimized_away that shouldn't be there.

-- 
           Summary: unreferenced nested inline functions not optimized away
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dank at kegel dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug optimization/15345] [3.4/3.5 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-09 18:59 -------
Confirmed, fixed already on the tree-ssa.  I do not know if this will get fixed for 3.4.1 at all.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |pessimizes-code
      Known to fail|                            |3.4.0 3.5.0
      Known to work|                            |tree-ssa 3.3.3
   Last reconfirmed|0000-00-00 00:00:00         |2004-05-09 18:59:11
               date|                            |
            Summary|unreferenced nested inline  |[3.4/3.5 Regression] [non-
                   |functions not optimized away|unit-at-a-time] unreferenced
                   |                            |nested inline functions not
                   |                            |optimized away
   Target Milestone|---                         |3.4.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-06-12 22:05 -------
Jan, please investigate this problem.  There are a lot of unit-at-a-time related
regressions targeted at 3.4.1; please look at all of them and indicate your
thoughts.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[jh at suse dot cz]

------- Additional Comments From jh at suse dot cz  2004-06-13 14:13 -------
Subject: Re:  [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

> 
> ------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-06-12 22:05 -------
> Jan, please investigate this problem.  There are a lot of unit-at-a-time related
> regressions targeted at 3.4.1; please look at all of them and indicate your
> thoughts.

I am still offline till day after tomorrow but I will look into that
afterwards.
The irritating thing about this testcase is that nested functions bypass
cgraph code completely on GCC before tree-ssa merge and thus it does not
deffer and elliminate it.
I am quite surprised that this used to be working on 2.95 and 3.2.  To
get it back I guess I will need to add some hacks into the frontend to
ask the cgraph about the reachability.

Honza


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[hubicka at gcc dot gnu dot org]

------- Additional Comments From hubicka at gcc dot gnu dot org  2004-06-21 17:47 -------
I've tried 3 different simple tricks to get this working right, but they've all failed in nasty interference in between trampolines and function ellimination.
Given the fact that nested functions are rarely used and ellimination of outline copy of function is not promised anywhere and that mainline already handles this right by unnesting, I would suggest to mark this as WONTFIX.
Honza

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-06-21 21:22 -------
Fixed in GCC 3.5; won't be fixed in GCC 3.4.x.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|3.4.1                       |3.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-07-09 16:48 -------
*** Bug 16450 has been marked as a duplicate of this bug. ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[jakub at gcc dot gnu dot org]

------- Additional Comments From jakub at gcc dot gnu dot org  2004-07-19 14:11 -------
This bug is IMHO very severe, it makes GCC 3.4.x totally unusable for glibc
builds as it almost doubles the size of the dynamic linker.
Can't this decision be reconsidered?

It worked just fine until GCC 3.3.x because of the DECL_DEFER_OUTPUT setting
in rest_of_compilation (now rest_of_handle_inlining).

I have played with:
--- gcc/toplev.c.jj        2004-02-20 19:37:45.000000000 +0100
+++ gcc/toplev.c    2004-07-19 15:50:30.985366840 +0200
@@ -2714,9 +2714,13 @@ rest_of_handle_inlining (tree decl)
             for unreferenced symbols.  See g77.f-torture/execute/980520-1.f.
             But removing this line from the check breaks all languages that
             use the call graph to output symbols.  This hard-coded check is
-            the least invasive work-around.  */
+            the least invasive work-around.
+            C nested functions need to be deferred here too, otherwise
+            they will be emitted even when never used.  */
          && (flag_inline_functions
-             || strcmp (lang_hooks.name, "GNU F77") == 0)
+             || strcmp (lang_hooks.name, "GNU F77") == 0
+             || (strcmp (lang_hooks.name, "GNU C") == 0
+                 && DECL_CONTEXT (decl)))
          && ((! TREE_PUBLIC (decl) && ! TREE_ADDRESSABLE (decl)
               && ! TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl))
               && ! flag_keep_inline_functions)

Honza, can you see what problems could this cause?

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[jh at suse dot cz]

------- Additional Comments From jh at suse dot cz  2004-07-19 15:43 -------
Subject: Re:  [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

> 
> ------- Additional Comments From jakub at gcc dot gnu dot org  2004-07-19 14:11 -------
> This bug is IMHO very severe, it makes GCC 3.4.x totally unusable for glibc
> builds as it almost doubles the size of the dynamic linker.
> Can't this decision be reconsidered?

Why exactly does glibc rely on elliminating unused nested functions?
> 
> It worked just fine until GCC 3.3.x because of the DECL_DEFER_OUTPUT setting
> in rest_of_compilation (now rest_of_handle_inlining).
> 
> I have played with:
> --- gcc/toplev.c.jj        2004-02-20 19:37:45.000000000 +0100
> +++ gcc/toplev.c    2004-07-19 15:50:30.985366840 +0200
> @@ -2714,9 +2714,13 @@ rest_of_handle_inlining (tree decl)
>              for unreferenced symbols.  See g77.f-torture/execute/980520-1.f.
>              But removing this line from the check breaks all languages that
>              use the call graph to output symbols.  This hard-coded check is
> -            the least invasive work-around.  */
> +            the least invasive work-around.
> +            C nested functions need to be deferred here too, otherwise
> +            they will be emitted even when never used.  */
>           && (flag_inline_functions
> -             || strcmp (lang_hooks.name, "GNU F77") == 0)
> +             || strcmp (lang_hooks.name, "GNU F77") == 0
> +             || (strcmp (lang_hooks.name, "GNU C") == 0
> +                 && DECL_CONTEXT (decl)))
>           && ((! TREE_PUBLIC (decl) && ! TREE_ADDRESSABLE (decl)
>                && ! TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl))
>                && ! flag_keep_inline_functions)
> 
> Honza, can you see what problems could this cause?

That might work (using the old deffering code path just didn't occured
to me).  Instead of relying on the hooks, I think we might simply use
cgraph_node (decl)->origin test so we won't mess up for methods (this is
why you need the checks for languages, right?)

Thanks!
Honza
> 
> -- 
> 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345
> 
> ------- You are receiving this mail because: -------
> You are on the CC list for the bug, or are watching someone who is.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-07-21 07:37 -------
Subject: Bug 15345

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_4-branch
Changes by:	jakub@gcc.gnu.org	2004-07-21 07:37:18

Modified files:
	gcc            : ChangeLog tree-optimize.c toplev.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/gcc.dg/torture: nested-fn-1.c 

Log message:
	PR middle-end/15345
	PR c/16450
	* toplev.c (rest_of_handle_inlining): Set DECL_DEFER_OUTPUT on C
	nested functions as well.
	* tree-optimize.c (tree_rest_of_compilation): Don't clear decl rtls
	for deferred nested inlines.
	
	* gcc.dg/torture/nested-fn-1.c: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=2.2326.2.563&r2=2.2326.2.564
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/tree-optimize.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=2.8.8.5&r2=2.8.8.6
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/toplev.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.863.4.10&r2=1.863.4.11
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.3389.2.231&r2=1.3389.2.232
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/torture/nested-fn-1.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=NONE&r2=1.1.2.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-07-21 07:39 -------
Subject: Bug 15345

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	jakub@gcc.gnu.org	2004-07-21 07:39:09

Modified files:
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/gcc.dg/torture: nested-fn-1.c 

Log message:
	PR middle-end/15345
	PR c/16450
	* gcc.dg/torture/nested-fn-1.c: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.4029&r2=1.4030
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/gcc.dg/torture/nested-fn-1.c.diff?cvsroot=gcc&r1=1.1&r2=1.2



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345

[Bug middle-end/15345] [3.4 Regression] [non-unit-at-a-time] unreferenced nested inline functions not optimized away

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to work|tree-ssa 3.3.3 3.5.0        |tree-ssa 3.3.3 3.5.0 3.4.2
   Target Milestone|3.5.0                       |3.4.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15345