[Bug target/29198] New: Incorrect reference to __thread array with -fPIC -O2 on x86

[Bug target/29198] New: Incorrect reference to __thread array with -fPIC -O2 on x86

[ian at airs dot com]

I compiled this C code with current mainline with -fPIC -O2 on x86 GNU/Linux:

extern int f2 (int, int, int, int);
struct s { char b[4]; };
__thread struct s a[2];
void f1 (int a1, int a2)
{
  int i, j;
  for (i = 0; i < 4; i++)
    {
      int tot = 0;
      for (j = 0; j < 4; j++)
        tot += f2 (a1, a2, i, j);
      a[0].b[i] = tot;
    }
 }

The resulting assembler file had this in it:

        movl    a@GOT(%ebx), %ecx

But a is declared with __thread.  This should instead be something like:

        leal    a@TLSGD(,%ebx,1), %eax
        call    ___tls_get_addr@PLT

In the real code there are other references to a, which leads to a linker
error:

`a' accessed both as normal and thread local symbol

I believe the bug is in legitimize_address or in legitimize_pic_address in
config/i386/i386.c.  legitimize_address gets called with

(plus:SI (reg/v:SI 64 [ i ])
    (symbol_ref:SI ("a") [flags 0x8] <var_decl 0xb7c630b0 a>))

When it sees a symbol as the right-hand operand of a PLUS, it calls
legitimize_pic_address.  That returns an UNSPEC_GOT.  Somewhere along the way,
it needs to call legitimize_tls_address.


-- 
           Summary: Incorrect reference to __thread array with -fPIC -O2 on
                    x86
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ian at airs dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198

[Bug target/29198] [4.0/4.1/4.2 Regression] Incorrect reference to __thread array with -fPIC -O2 on x86

[pinskia at gcc dot gnu dot org]

------- Comment #1 from pinskia at gcc dot gnu dot org  2006-09-24 05:29 -------
Confirmed, this testcase worked in 3.4.0 but that might just mean this is a
latent bug.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |wrong-code
      Known to fail|                            |4.0.0 4.1.0 4.2.0
      Known to work|                            |3.4.0
   Last reconfirmed|0000-00-00 00:00:00         |2006-09-24 05:29:30
               date|                            |
            Summary|Incorrect reference to      |[4.0/4.1/4.2 Regression]
                   |__thread array with -fPIC - |Incorrect reference to
                   |O2 on x86                   |__thread array with -fPIC -
                   |                            |O2 on x86
   Target Milestone|---                         |4.0.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198

[Bug target/29198] [4.0/4.1/4.2 Regression] Incorrect reference to __thread array with -fPIC -O2 on x86

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2006-09-24 05:31 -------
I should note that -fno-ivopts causes to produce the correct result for this
testcase.  I am going to try to find a testcase that fails even with 3.4.0.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198

[Bug target/29198] [4.0/4.1/4.2 Regression] Incorrect reference to __thread array with -fPIC -O2 on x86

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2006-09-24 05:34 -------
Here is a testcase which shows this is a latent bug:
extern int f2 (int, int, int, int);
struct s { char b[4]; };
__thread struct s a[2];
void f1 (int a1, int a2)
{
  int i, j;
  for (i = 0; i < 4; i++)
    {
      int tot = 0;
      for (j = 0; j < 4; j++)
        tot += f2 (a1, a2, i, j);
      *(&a[0].b[0] + i) = tot;
    }
 }


------
But since the orginal testcase worked in 3.4.0, this should be still marked as
a regression, IV-OPTs is causing the latent bug to show up.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198

[Bug target/29198] [4.0/4.1/4.2 Regression] Incorrect reference to __thread array with -fPIC -O2 on x86

[jakub at gcc dot gnu dot org]

-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jakub at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2006-09-24 05:29:30         |2006-09-29 11:29:51
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198

[Bug target/29198] [4.0/4.1/4.2 Regression] Incorrect reference to __thread array with -fPIC -O2 on x86

[mmitchel at gcc dot gnu dot org]

------- Comment #4 from mmitchel at gcc dot gnu dot org  2006-10-01 22:59 -------
I'm marking this P2, rather than P1, because the use of TLS structures seems a
bit of a corner-case.  Feel free to lobby to make this a P1.


-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198

[Bug target/29198] [4.0/4.1/4.2 Regression] Incorrect reference to __thread array with -fPIC -O2 on x86

[jakub at gcc dot gnu dot org]

------- Comment #5 from jakub at gcc dot gnu dot org  2006-10-06 07:25 -------
Subject: Bug 29198

Author: jakub
Date: Fri Oct  6 07:25:02 2006
New Revision: 117483

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=117483
Log:
        PR target/29198
        * config/i386/i386.c (legitimize_pic_address): Reject TLS symbols.
        * config/i386/predicates.md (local_symbolic_operand): Likewise.

        * gcc.dg/tls/opt-12.c: New test.

Added:
    trunk/gcc/testsuite/gcc.dg/tls/opt-12.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/i386.c
    trunk/gcc/config/i386/predicates.md
    trunk/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198

[Bug target/29198] [4.0/4.1/4.2 Regression] Incorrect reference to __thread array with -fPIC -O2 on x86

[jakub at gcc dot gnu dot org]

------- Comment #6 from jakub at gcc dot gnu dot org  2006-10-06 07:35 -------
Subject: Bug 29198

Author: jakub
Date: Fri Oct  6 07:35:45 2006
New Revision: 117486

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=117486
Log:
        PR target/29198
        * config/i386/i386.c (legitimize_pic_address): Reject TLS symbols.
        * config/i386/predicates.md (local_symbolic_operand): Likewise.

        * gcc.dg/tls/opt-12.c: New test.

Added:
    branches/gcc-4_1-branch/gcc/testsuite/gcc.dg/tls/opt-12.c
Modified:
    branches/gcc-4_1-branch/gcc/ChangeLog
    branches/gcc-4_1-branch/gcc/config/i386/i386.c
    branches/gcc-4_1-branch/gcc/config/i386/predicates.md
    branches/gcc-4_1-branch/gcc/testsuite/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198

[Bug target/29198] [4.0 Regression] Incorrect reference to __thread array with -fPIC -O2 on x86

[jakub at gcc dot gnu dot org]

------- Comment #7 from jakub at gcc dot gnu dot org  2006-10-06 07:41 -------
Fixed on the trunk and on 4.1 branch.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|4.0.0 4.1.0 4.2.0           |4.0.0 4.1.0 4.1.1
      Known to work|3.4.0                       |3.4.0 4.1.2 4.2.0
            Summary|[4.0/4.1/4.2 Regression]    |[4.0 Regression] Incorrect
                   |Incorrect reference to      |reference to __thread array
                   |__thread array with -fPIC - |with -fPIC -O2 on x86
                   |O2 on x86                   |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198

[Bug target/29198] [4.0 Regression] Incorrect reference to __thread array with -fPIC -O2 on x86

[gdr at gcc dot gnu dot org]

------- Comment #8 from gdr at gcc dot gnu dot org  2007-02-03 20:22 -------
Fixed in GCC-4.1.2.


-- 

gdr at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29198