[Bug debug/45299] New: Dwarf information is wrong with optimised code.

[Bug debug/45299] New: Dwarf information is wrong with optimised code.

[hariharans at picochip dot com]

I saw this problem initially on 4.5.0 compiler, but the same problem happens on
mainline too. In function arraysum in the attached example, the parameter
array, which is a pointer to array of


-- 
           Summary: Dwarf information is wrong with optimised code.
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: hariharans at picochip dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: picochip-unknown-none


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299

[Bug debug/45299] Dwarf information is wrong with optimised code.

[hariharans at picochip dot com]

------- Comment #1 from hariharans at picochip dot com  2010-08-16 16:17 -------
Sorry for the incomplete description. The actual description:

I saw this problem initially on 4.5.0 compiler, but the same problem happens on
mainline too. In function arraysum in the attached example, the parameter
array, which is a pointer to array of int actually gets reflected in dwarf
wrong. The dwarf reader that we have says this

      <0x457> (15) Inlined subroutine: "arraySum"
        Called from:
          File: /home/gccuser/Tools/Verification/Debugger/symbolic/symbolic.vhd
          Line: 603
          Column: 0
        Address Ranges: [0x40, 0x63) 
        <0x463> (16) Parameter:
          Name: size
          Type: <0x35a>
          Location: DW_OP_reg1 
        <0x46a> (17) Parameter:
          Name: array
          Type: <0x3f3>
          Location: 
        [47, 51) : DW_OP_reg0 

In the range [47,51) array parameter resides in reg0, according to dwarf. This
is valid only at instruction at 47.  The instruction does this.

ldw (r0)0, r0

So, r0 now contains the first value in the array instead of the address and
hence the dwarf is wrong for the rest of this address range.

Disabling VTA means most of the variables in this testcase become "Not
Present".

I will add the source file, assembly and address encoded assembly so you can
see what is going on. Please let me know if you need any other information.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299

[Bug debug/45299] Dwarf information is wrong with optimised code.

[hariharans at picochip dot com]

------- Comment #2 from hariharans at picochip dot com  2010-08-16 16:19 -------
Created an attachment (id=21492)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21492&action=view)
The source code


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299

[Bug debug/45299] Dwarf information is wrong with optimised code.

[hariharans at picochip dot com]

------- Comment #4 from hariharans at picochip dot com  2010-08-16 16:24 -------
Created an attachment (id=21494)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21494&action=view)
assembly code


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299

[Bug debug/45299] Dwarf information is wrong with optimised code.

[hariharans at picochip dot com]

------- Comment #3 from hariharans at picochip dot com  2010-08-16 16:23 -------
Created an attachment (id=21493)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21493&action=view)
The source code


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hariharans at picochip dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #21492|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299

[Bug debug/45299] Dwarf information is wrong with optimised code.

[hariharans at picochip dot com]

------- Comment #5 from hariharans at picochip dot com  2010-08-16 16:28 -------
Created an attachment (id=21495)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21495&action=view)
address encoded assembly


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299

[Bug target/45299] Dwarf information is wrong with optimised code.

[jakub at gcc dot gnu dot org]

------- Comment #6 from jakub at gcc dot gnu dot org  2010-08-17 10:06 -------
Sounds like a target bug.
After variable_tracking_main the notes look correct:
(note 88 23 89 2 (var_location array (reg:HI 0 R0 [ pass_through_array ]))
NOTE_INSN_VAR_LOCATION)

(note 89 88 90 2 (var_location size (reg:HI 1 R1 [ pass_through_size ]))
NOTE_INSN_VAR_LOCATION)

(note 90 89 32 2 (var_location i (const_int 0 [0])) NOTE_INSN_VAR_LOCATION)

(insn:TI 32 90 91 2 (set (reg/v:HI 0 R0 [orig:50 sum ] [50])
        (mem:HI (reg/f:HI 0 R0 [orig:62 pass_through_array ] [62]) [2
*pass_through_array_1(D)+0 S2 A16])) b45299.c:12 15 {movhi}
     (nil))

(note 91 32 92 2 (var_location pass_through_array (reg/v/f:HI 5 R5 [orig:62
pass_through_array ] [62])) NOTE_INSN_VAR_LOCATION)

(note 92 91 93 2 (var_location array (reg/v/f:HI 5 R5 [orig:62
pass_through_array ] [62])) NOTE_INSN_VAR_LOCATION)

but then reorder_var_tracking_notes drops some notes on the floor and moves
others.  Clearly a target bug.  Dropping on the floor is certainly wrong, and
the moving results in invalid debug info too.


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jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|debug                       |target
           Keywords|wrong-debug                 |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299

[Bug target/45299] Dwarf information is wrong with optimised code.

[hariharans at picochip dot com]

------- Comment #7 from hariharans at picochip dot com  2010-08-28 16:14 -------
picochip is a vliw processor and reorder_var_tracking_notes tries to move debug
instructions from middle of vliw instructions out. There was a bug in that
which resulted in this problem. 


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299

[Bug target/45299] Dwarf information is wrong with optimised code.

[hariharans at picochip dot com]

------- Comment #8 from hariharans at picochip dot com  2010-08-28 16:15 -------
Created an attachment (id=21585)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=21585&action=view)
Patch to fix the problem


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299

[Bug target/45299] Dwarf information is wrong with optimised code.

[hariharans at picochip dot com]

------- Comment #9 from hariharans at picochip dot com  2010-08-28 17:17 -------
Fixed on mainline.


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hariharans at picochip dot com changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45299