[Bug target/14346] New: With -fpic/-fPIC, thunks jump through PLT, not directly to thunked function

[Bug target/14346] New: With -fpic/-fPIC, thunks jump through PLT, not directly to thunked function

[hp at gcc dot gnu dot org]

As in summary.  Because thunks do not set up the PIC register, going through the
PLT causes a SEGV in best case.  Another PIC construct than for normal calls
must be used, but unfortunately the only (currently) available PC-relative PIC
reloc for cris-axis-linux-gnu requests a PLT.  The thunked function is global. 
Using a local symbol makes the linker omit the redirection through the PLT and
the jump goes directly to the right place.

On trunk and 3.4 branch, the thunk uses a local symbol (equated to the thunked
function, generated by generic code), so TRT happens.
See <URL:http://gcc.gnu.org/ml/gcc-patches/2003-06/msg02603.html> for
the first of the patch where the generic local-thunk was implemented (needed
follow-up patches for correctness).  I'll go with a target-local patch.

Testcase:
-------------- th1.h
class B
{
  int bb1;
  int bb2;
 public:
  virtual void b();
};
extern class B* mka();
-------------- th1.cc (compile and link with -fpic -shared -o libth1.so)
#include "th1.h"
class A
{
  int aa;
public:
  virtual void a() = 0;
};

class C : public A, public B
{
  int cc;
public:
  virtual void b();
  virtual void a();
};

extern "C" void abort (void);
extern "C" void exit (int);

class B* mka (void)
{
  return new C;
}

void C::b(void)
{
  exit (0);
}

void B::b(void)
{
  abort ();
}

void C::a(void)
{
  abort ();
}
-------------- m.cc (compile and link with -L. -lth1, expect normal exit)

#include "th1.h"
extern "C" void abort (void);
int ii[10];
int main(void)
{
  register int picreg
#if defined (__CRIS__) && !defined (__PIC__) && !defined (__pic__)
    __asm__ ("r0")
#endif
    = -1;
  class B *bb = mka();
  bb->b();
  // Make sure picreg is alive and used after bb->b() above.
  asm ("" : : "r" (picreg));
  abort ();
}

-- 
           Summary: With -fpic/-fPIC, thunks jump through PLT, not directly
                    to thunked function
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P1
         Component: target
        AssignedTo: hp at gcc dot gnu dot org
        ReportedBy: hp at gcc dot gnu dot org
                CC: gcc-bugs at gcc dot gnu dot org
GCC target triplet: cris-axis-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14346

[Bug target/14346] With -fpic/-fPIC, thunks jump through PLT, not directly to thunked function

[hp at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2004-02-29 16:14:01
               date|                            |
   Target Milestone|---                         |3.3.4
            Version|unknown                     |3.2.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14346

[Bug target/14346] [3.3 only] With -fpic/-fPIC, thunks jump through PLT, not directly to thunked function

[hp at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |critical


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14346

[Bug target/14346] [3.3 only] With -fpic/-fPIC, thunks jump through PLT, not directly to thunked function

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-02-29 21:46 -------
Subject: Bug 14346

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_3-branch
Changes by:	hp@gcc.gnu.org	2004-02-29 21:46:29

Modified files:
	gcc            : ChangeLog 
	gcc/config/cris: cris.c 

Log message:
	PR target/14346
	* config/cris/cris.c (cris_asm_output_mi_thunk): For PIC, prepend
	TAB to jumping "add.d" insn.  Avoid PLT indirection by equating a
	local symbol and jumping through it.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.16114.2.913&r2=1.16114.2.914
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/config/cris/cris.c.diff?cvsroot=gcc&only_with_tag=gcc-3_3-branch&r1=1.32.4.2&r2=1.32.4.3



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14346

[Bug target/14346] [3.3 only] With -fpic/-fPIC, thunks jump through PLT, not directly to thunked function

[hp at gcc dot gnu dot org]

------- Additional Comments From hp at gcc dot gnu dot org  2004-02-29 21:52 -------
See <URL:http://gcc.gnu.org/ml/gcc-patches/2004-02/msg02798.html>.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14346