[Bug debug/23551] dwarf records for inlines appear incomplete

[Bug debug/23551] dwarf records for inlines appear incomplete

[mfortune at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

Matthew Fortune <mfortune at gmail dot com> changed:

           What    |Removed                     |Added
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                 CC|                            |mfortune at gmail dot com

--- Comment #19 from Matthew Fortune <mfortune at gmail dot com> 2011-04-21 14:07:35 UTC ---
I have one further case that may be worth adding to this ticket which relates
to the order of formal paramters emitted for an inlined subroutine in debug
info.

GCC currently emits formal parameter DIEs for an inlined subroutine in reverse
order to the function's parameters. The DWARF spec is slightly unclear in this
area but does indicate that formal parameters must appear in the same order as
listed in the function prototype in both abstract and concrete instances.

One potential fix would be to change setup_one_parameter in tree-inline.c to
append each new VAR_DECL to the vars list instead of prepend them. There may
however be a more elegant approach by modifying the dwarf engine to detect and
re-order VAR_DECLs that relate to formal paramters and emit them in the correct
order.

If this would be best as a separate ticket then I will open one.

[Bug debug/23551] dwarf records for inlines appear incomplete

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

Richard Biener <rguenth at gcc dot gnu.org> changed:

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

--- Comment #21 from Richard Biener <rguenth at gcc dot gnu.org> ---
There is PR103047 for that now.

[Bug debug/23551] dwarf records for inlines appear incomplete

[aoliva at gcc dot gnu dot org]

------- Comment #18 from aoliva at gcc dot gnu dot org  2007-07-09 19:24 -------
Subject: Bug 23551

Author: aoliva
Date: Mon Jul  9 19:24:23 2007
New Revision: 126492

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=126492
Log:
Revert:
2007-07-06  Alexandre Oliva  <aoliva@redhat.com>
PR debug/23551
* tree-ssa-copyrename.c (copy_rename_partition_coalesce):
Disregard DECL_FROM_INLINE.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-ssa-copyrename.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[aoliva at gcc dot gnu dot org]

------- Comment #17 from aoliva at gcc dot gnu dot org  2007-07-06 08:38 -------
Subject: Bug 23551

Author: aoliva
Date: Fri Jul  6 08:38:40 2007
New Revision: 126402

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=126402
Log:
PR debug/23551
* tree-ssa-copyrename.c (copy_rename_partition_coalesce):
Disregard DECL_FROM_INLINE.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/tree-ssa-copyrename.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[patchapp at dberlin dot org]

------- Comment #16 from patchapp at dberlin dot org  2007-05-10 08:40 -------
Subject: Bug number PR 23551

A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2007-05/msg00703.html


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[fche at redhat dot com]

------- Comment #15 from fche at redhat dot com  2007-03-30 22:10 -------
(In reply to comment #14)
> This is basically the same as case 1 (though a constant instead of a call to
> rand()), now do we want not to prop x1 into x?  I say we always do want that
> because otherwise we get an extra assignment.

I believe the idea was to emit extra DWARF for that copy-propagation, so as to
treat the destination as a location-list-level alias of the source.  The idea
was not to inhibit the copy, just to "document it", if that is sensible &
feasible.

> Plus this issue is not a regression at all because the RTL level does the same.

(Did someone say it was?)


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[pinskia at gcc dot gnu dot org]

------- Comment #14 from pinskia at gcc dot gnu dot org  2007-03-30 22:04 -------
(In reply to comment #13)
> If aoliva is correct in comment# 11, then some information is being lost
> that could be retained with some additional effort.  That would make this
> bug other than invalid - at best a wontfix.

Lets look at this again. A simplified testcase without inlining:
int main ()
{
  int x1 = 3;
  {
  int x = x1;
  int i = 0;
  for (i = 0; i < x; ++i)
    x += i;
  return x;
  }
}

This is basically the same as case 1 (though a constant instead of a call to
rand()), now do we want not to prop x1 into x?  I say we always do want that
because otherwise we get an extra assignment.  Plus this issue is not a
regression at all because the RTL level does the same.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[fche at redhat dot com]

------- Comment #13 from fche at redhat dot com  2007-03-30 19:21 -------
> Case 1, is also too hard to fix as it would make us lose a lot of
> optimizations.

If aoliva is correct in comment# 11, then some information is being lost
that could be retained with some additional effort.  That would make this
bug other than invalid - at best a wontfix.


-- 

fche at redhat dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[pinskia at gcc dot gnu dot org]

------- Comment #12 from pinskia at gcc dot gnu dot org  2006-12-09 05:43 -------
Case 2 was filed as PR 29792 and was declared invalid.
Though we get currently:
        .uleb128 0x2    # (DIE (0x25) DW_TAG_subprogram)
        .ascii "foo\0"  # DW_AT_name
        .byte   0x1     # DW_AT_decl_file (no-inlined-instance-record.c)
        .byte   0x2     # DW_AT_decl_line
        .byte   0x1     # DW_AT_prototyped
        .long   0x40    # DW_AT_type
        .byte   0x3     # DW_AT_inline
        .long   0x40    # DW_AT_sibling
        .uleb128 0x3    # (DIE (0x36) DW_TAG_formal_parameter)
        .ascii "x\0"    # DW_AT_name
        .byte   0x1     # DW_AT_decl_file (no-inlined-instance-record.c)
        .byte   0x1     # DW_AT_decl_line
        .long   0x40    # DW_AT_type
        .byte   0x0     # end of children of DIE 0x25


Case 1, is also too hard to fix as it would make us lose a lot of
optimizations.

Really what GCC is producing is the best debugging you can get for these
functions.


-- 

pinskia at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[aoliva at gcc dot gnu dot org]

------- Comment #11 from aoliva at gcc dot gnu dot org  2006-11-01 06:37 -------
Every inlined function starts with copying of argument initializers into the
formal arguments.  This makes such copies too suitable for SSA coalescing.

It appears to me that it would be desirable to arrange for coalescing to
somehow preserve information as to which variables have been coalesced, such
that we can emit debug info for all coalesced variables, not just one of them.

It sounds like a lot of work, though.


-- 

aoliva at gcc dot gnu dot org changed:

           What    |Removed                     |Added
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                 CC|                            |aoliva at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[drow at gcc dot gnu dot org]

------- Comment #10 from drow at gcc dot gnu dot org  2006-07-21 16:57 -------
(In reply to comment #9)
> Case 1:
> There is no location info for the parameter x because it has been optimized
> away.  Change the variable x in main to y to avoid ambiguity, compile with
> -fdump-tree-all, and look at the t27 and t29 dumps.  In the t27 dump, the
> variable x is there and assigned to.  In the t29 dump, the variable x is there,
> but no longer assigned to.  Since it is no longer assigned to, we never
> allocate space for it, and hence no location attribute can be emitted.  t29 is
> the copyrename dump file.  If I compile with -fno-tree-copyrename, then I do
> get a location attribute for the parameter x in the inlined copy of foo.  I
> don't think there is any bug here, but if there is, it would be in the tree
> copyrename pass, because there is no longer any useful parameter x when it is
> done.

For the record, I encountered this problem today also (formals with no location
information).  Not a single argument had a location.  Adding
-fno-tree-copyrename fixed one (of about seven).  In this case the variables
are all used, mostly in non-trivial ways.  My testcase was eval.c from GDB; the
function evaluate_struct_tuple is inlined and debugging into it is quite hard. 
I'm working on improving this in GDB, but I can't improve where the compiler
gives me nothing to work with.

We already know that there are many similar problems in the tree optimizers;
I'm just adding a data point.


-- 

drow at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-07-21 16:57:25
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[wilson at gcc dot gnu dot org]

------- Comment #9 from wilson at gcc dot gnu dot org  2005-10-13 02:47 -------
If you compile with -dA you will get readable DWARF2 debug info in the .s file.

Case 1:
There is no location info for the parameter x because it has been optimized
away.  Change the variable x in main to y to avoid ambiguity, compile with
-fdump-tree-all, and look at the t27 and t29 dumps.  In the t27 dump, the
variable x is there and assigned to.  In the t29 dump, the variable x is there,
but no longer assigned to.  Since it is no longer assigned to, we never
allocate space for it, and hence no location attribute can be emitted.  t29 is
the copyrename dump file.  If I compile with -fno-tree-copyrename, then I do
get a location attribute for the parameter x in the inlined copy of foo.  I
don't think there is any bug here, but if there is, it would be in the tree
copyrename pass, because there is no longer any useful parameter x when it is
done.

Case 2:
Similar situation.  The tree-ssa optimizers optimize away all trace of the
inline foo function.  By the time we get to the end of tree-ssa, all we have
left is return 11.  If you look in the .00.expand RTL dump, there are no line
number notes or basic block notes associated with the inline foo.  Since there
is no inline foo, the debug output routines can't do anything here.  I tried
all of the -fno-tree-* options, but that doesn't help.  This is apparently
something that can't be turned off.  If we really want debug info in this case,
then the tree optimizers need to be modified to preserve lexical blocks and
variables that originated in inlined functions.  Not clear if this is
desirable.

Case 3:
The difference here is that the tree optimizers are not able to completely
optimize away the for loop in the inline function.  Since we still have lines
of code from the inline function, and stores to the parameter x, when the
tree-ssa optimizers are done, we get the debug info you expect.

Summary, these problems are all issues with tree optimizers destroying info
when optimizing.  Case 1 probably can't be fixed without hurting optimization,
and hence is probably not feasible to fix it.  A partial fix to Case 2 may be
feasible, as the tree optimizers can perhaps be taught to keep the lexical
block needed to represent the inline function foo.  However, as in case 1,
there will be no location attribute for x though, and this can't be fixed
without disabling optimizations.  Case 3 is the good example, there is nothing
broken here.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2005-08-24 21:08 -------
A lot of these are all because we optimize stuff away. like the no-inlined-subroutine is because we just 
get "return 11;".

Others look like they are fixed in 4.1.0.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[graydon at redhat dot com]

------- Additional Comments From graydon at redhat dot com  2005-08-24 20:59 -------
I should also point out that the compile flags for these cases were always
"-finline -O2 -g"; I'm not sure how best to tell gcc to enable function-inlining
(and nothing else), so this might be a mistake on my part. The cases are small
enough that you can retry them on other flags and experiment.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[graydon at redhat dot com]

------- Additional Comments From graydon at redhat dot com  2005-08-24 20:55 -------
Created an attachment (id=9582)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9582&action=view)
case 3, debug info dump


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[graydon at redhat dot com]

------- Additional Comments From graydon at redhat dot com  2005-08-24 20:54 -------
Created an attachment (id=9581)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9581&action=view)
case 3, preprocessed file


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[graydon at redhat dot com]

------- Additional Comments From graydon at redhat dot com  2005-08-24 20:54 -------
Created an attachment (id=9580)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9580&action=view)
case 2, debug info dump


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[graydon at redhat dot com]

------- Additional Comments From graydon at redhat dot com  2005-08-24 20:53 -------
Created an attachment (id=9579)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9579&action=view)
case 2, preprocessed file


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[graydon at redhat dot com]

------- Additional Comments From graydon at redhat dot com  2005-08-24 20:52 -------
Created an attachment (id=9578)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9578&action=view)
case 1, debug info dump


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551

[Bug debug/23551] dwarf records for inlines appear incomplete

[graydon at redhat dot com]

------- Additional Comments From graydon at redhat dot com  2005-08-24 20:52 -------
Created an attachment (id=9577)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9577&action=view)
case 1, preprocessed file


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23551