[Bug debug/44610] New: VTA produces wrong variable location information

[Bug debug/44610] New: VTA produces wrong variable location information

[hariharans at picochip dot com]

If i compile the attached testcase for picochip under -O2, i get the following
location information for variable arg0 in main.

.ascii 16#61# 16#72# 16#67# 16#30# 16#0#   ; arg0\0
.initByte 0x1
.initByte 0x2a
.unalignedInitLong 0x9e
.initByte 0xc
.initByte 0x5b
.initByte 0x93
        .uleb128 0x2
.initByte 0x5b
.initByte 0x93
        .uleb128 0x2
.initByte 0x5b
.initByte 0x93
        .uleb128 0x2
.initByte 0x5b
.initByte 0x93
        .uleb128 0x2
        .uleb128 0xc
.unalignedInitLong _picoMark_Ldebug_ranges0+0xc
        .uleb128 0xa

which my dwarflib reader translates to mean

      <0x42f> (19) Lexical Block:
        Address Ranges: [0x18, 0x8d) [0x94, 0x99)
        <0x434> (20) Data:
          Name: arg0
          Type: <0xe0>
          Is External: false
          Location: DW_OP_reg11 DW_OP_piece: 2 DW_OP_reg11 DW_OP_piece: 2
DW_OP_reg11 DW_OP_piece: 2 DW_OP_reg11 DW_OP_piece: 2

R11 obviously does not contain all 4 piece os this 8-byte variable (a register
is 16-bit in picochip). I have tried to see if this was bug 43982, but the
mainline as of 20Jun with fix for that bug still reproduces this problem. 

The problem with this is that it doesn't actually say variable value is not
present, which is generally okay with -O2. It just gives wrong value silently!
Can you have a look at this, please?

I will attach the source file and the assembly. Please ask me if you need any
other information.


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           Summary: VTA produces wrong variable location information
           Product: gcc
           Version: 4.5.0
            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=44610

[Bug debug/44610] VTA produces wrong variable location information

[hariharans at picochip dot com]

------- Comment #1 from hariharans at picochip dot com  2010-06-21 13:55 -------
Created an attachment (id=20961)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20961&action=view)
The test sourcecode


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44610

[Bug debug/44610] VTA produces wrong variable location information

[hariharans at picochip dot com]

------- Comment #2 from hariharans at picochip dot com  2010-06-21 13:56 -------
Created an attachment (id=20962)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20962&action=view)
The test assembly


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44610

[Bug debug/44610] VTA produces wrong variable location information

[hariharans at picochip dot com]

------- Comment #3 from hariharans at picochip dot com  2010-06-21 13:59 -------
In my first comment, bug 43982 should have been bug 43983


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44610

[Bug debug/44610] VTA produces wrong variable location information

[aoliva at gcc dot gnu dot org]

------- Comment #4 from aoliva at gcc dot gnu dot org  2010-06-23 04:30 -------
Mine


-- 

aoliva at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |aoliva at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2010-06-23 04:30:09
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44610

[Bug debug/44610] VTA produces wrong variable location information

[aoliva at gcc dot gnu dot org]

------- Comment #5 from aoliva at gcc dot gnu dot org  2010-06-23 04:35 -------
Created an attachment (id=20984)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=20984&action=view)
Patch that fixes the problem

The MEMs for each HImode in the DImode args all have NULL MEM_OFFSET (we indeed
don have a constant offset within the loop, for it varies), but when we
delegitimize those addresses during var-tracking, we assume no MEM_OFFSET means
zero MEM_OFFSET, which maps all MEMs to the same VALUE.  The assumption turns
out to be wrong.  We can't delegitimize a MEM to the base address when it may
be offset by an unknown amount.  Testing the patch now.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44610

[Bug debug/44610] VTA produces wrong variable location information

[aoliva at gcc dot gnu dot org]

------- Comment #6 from aoliva at gcc dot gnu dot org  2010-06-25 21:11 -------
Subject: Bug 44610

Author: aoliva
Date: Fri Jun 25 21:11:32 2010
New Revision: 161413

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=161413
Log:
PR debug/44610
* simplify-rtx.c (delegitimize_mem_from_attrs): Don't use a base
address if the offset is unknown.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/simplify-rtx.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44610

[Bug debug/44610] VTA produces wrong variable location information

[aoliva at gcc dot gnu dot org]

------- Comment #7 from aoliva at gcc dot gnu dot org  2010-06-25 21:12 -------
Subject: Bug 44610

Author: aoliva
Date: Fri Jun 25 21:11:56 2010
New Revision: 161414

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=161414
Log:
PR debug/44610
* simplify-rtx.c (delegitimize_mem_from_attrs): Don't use a base
address if the offset is unknown.

Modified:
    branches/gcc-4_5-branch/gcc/ChangeLog
    branches/gcc-4_5-branch/gcc/simplify-rtx.c


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44610

[Bug debug/44610] VTA produces wrong variable location information

[aoliva at gcc dot gnu dot org]

------- Comment #8 from aoliva at gcc dot gnu dot org  2010-06-25 21:13 -------
Fixed


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aoliva at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44610