Bug 41558 - gfortran -O code excessive DW_OP_deref's
Summary: gfortran -O code excessive DW_OP_deref's
Status: RESOLVED FIXED
Alias: None
Product: gcc
Classification: Unclassified
Component: debug (show other bugs)
Version: 4.5.0
: P3 normal
Target Milestone: ---
Assignee: Jakub Jelinek
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2009-10-03 19:10 UTC by Jan Kratochvil
Modified: 2009-10-12 19:09 UTC (History)
3 users (show)

See Also:
Host:
Target: x86_64-unknown-linux-gnu
Build:
Known to work:
Known to fail:
Last reconfirmed:

Attachments
gcc45-pr41558.patch (4.74 KB, patch)
2009-10-05 09:52 UTC, Jakub Jelinek 		Details | Diff
View All Add an attachment (proposed patch, testcase, etc.)

Note You need to log in before you can comment on or make changes to this bug.
Description Jan Kratochvil 2009-10-03 19:10:47 UTC 
GNU Fortran (GCC) 4.5.0 20091003 (experimental)

  subroutine f(s)
  character*3 s
  s = s
  end
  call f ('foo')
  end

gdb -nx -ex 'b 3' -ex r -ex 'p s' ./file
->
Cannot access memory at address 0x6f6f66

 <2><4a>: Abbrev Number: 3 (DW_TAG_formal_parameter)
    <4b>   DW_AT_name        : s        
    <4f>   DW_AT_type        : <0x64>   
    <53>   DW_AT_location    : 4 byte block: 75 0 6 6   (DW_OP_breg5: 0; DW_OP_deref; DW_OP_deref)

If I patch those two DW_OP_deref -> DW_OP_nop then GDB prints:
$1 = 'foo'

gfortran -o 1 1.f90 -Wall -g -O1 

currently:
.LC0:
        .ascii  "foo"
...
        movl    $.LC0, %edi
...
        .byte   0x4     # DW_AT_location
        .byte   0x75    # DW_OP_breg5
        .sleb128 0
        .byte   0x6     # DW_OP_deref
        .byte   0x6     # DW_OP_deref
Comment 1 Jakub Jelinek 2009-10-05 09:52:24 UTC 
Created attachment 18706 [details]
gcc45-pr41558.patch

Patch I'm going to bootstrap/regtest.

BTW, gdb 7.0.50.20091005-cvs doesn't work with the guality.exp testcases well, something broke in it recently.  6.8.91.20090917-1.fc12 works fine.
Comment 2 Jakub Jelinek 2009-10-05 19:51:12 UTC 
Subject: Bug 41558

Author: jakub
Date: Mon Oct  5 19:50:57 2009
New Revision: 152467

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=152467
Log:
	PR debug/41558
	* dwarf2out.c (loc_by_reference): Removed.
	(dw_loc_list_1): New function.
	(dw_loc_list): Remove toplev argument, add want_address argument.
	Don't look at decl_by_reference_p at all.  Use dw_loc_list_1.
	(loc_list_from_tree) <case VAR_DECL>: Pass want_address rather than
	want_address == 2 to dw_loc_list.  For successful dw_loc_list
	set have_address to 1 only if want_address is not 0.

	* gcc.dg/guality/guality.exp: Move gdb-test proc into...
	* lib/gcc-gdb-test.exp: ... here.  New file.
	* gfortran.dg/guality/guality.exp: New file.
	* gfortran.dg/guality/pr41558.f90: New test.
	* gfortran.dg/guality/arg1.f90: New test.

Added:
    trunk/gcc/testsuite/gfortran.dg/guality/
    trunk/gcc/testsuite/gfortran.dg/guality/arg1.f90
    trunk/gcc/testsuite/gfortran.dg/guality/guality.exp
    trunk/gcc/testsuite/gfortran.dg/guality/pr41558.f90
    trunk/gcc/testsuite/lib/gcc-gdb-test.exp
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/dwarf2out.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/guality/guality.exp
Comment 3 Jan Kratochvil 2009-10-06 15:28:07 UTC 
(In reply to comment #1)
> BTW, gdb 7.0.50.20091005-cvs doesn't work with the guality.exp testcases well,
> something broke in it recently.  6.8.91.20090917-1.fc12 works fine.

There is an array with variable size: integer :: a(n), n
VLA support is still missing in FSF GDB, it is present in Archer (+Fedora) branch archer-jankratochvil-vla:
http://sourceware.org/gdb/wiki/ArcherBranchManagement
Comment 4 Jakub Jelinek 2009-10-12 19:09:24 UTC 
Fixed.