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From: Ulrich Weigand <weigand@immd1.informatik.uni-erlangen.de>
Message-Id: <200305070113.DAA15839@faui11.informatik.uni-erlangen.de>
Subject: Re: GCC 3.3 Prelease broken on s390
To: rth@redhat.com
Date: Wed, 07 May 2003 01:13:00 -0000
Cc: mark@codesourcery.com, gcc@gcc.gnu.org
In-Reply-To: <no.id> from "weigand" at May 07, 2003 02:24:35 AM
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I wrote:

> Interestingly, mainline works fine without any patch.

When your latest mainline patch to unwind-dw2.c is backported 
to 3.3, it works again as well; the patch below does this.

(A full bootstrap/regtest is still running.)

Note that I really only need the first hunk, as the
rest only changes the return value from uw_install_context_1,
which is completely ignored on s390 anyway (as SP is
restored from its stack slot, where the correct new
value was already stored by uw_install_context_1).

What do you think?

Bye,
Ulrich

ChangeLog:

        * unwind-dw2.c (uw_update_context_1): Only set cfa as sp if
        previous frame didn't save sp.  Clear sp for next frame.
        (uw_install_context_1): Honor saved sp from frame.


*** unwind-dw2.c.orig	Wed May  7 02:52:49 2003
--- unwind-dw2.c	Wed May  7 03:00:45 2003
*************** uw_update_context_1 (struct _Unwind_Cont
*** 1059,1069 ****
       In very special situations (such as unwind info for signal return),
       there may be location expressions that use the stack pointer as well.
  
!      Given that other unwind mechanisms generally won't work if you try
!      to represent stack pointer saves and restores directly, we don't
!      bother conditionalizing this at all.  */
!   tmp_sp = (_Unwind_Ptr) context->cfa;
!   orig_context.reg[__builtin_dwarf_sp_column ()] = &tmp_sp;
  
    /* Compute this frame's CFA.  */
    switch (fs->cfa_how)
--- 1059,1075 ----
       In very special situations (such as unwind info for signal return),
       there may be location expressions that use the stack pointer as well.
  
!      Do this conditionally for one frame.  This allows the unwind info
!      for one frame to save a copy of the stack pointer from the previous
!      frame, and be able to use much easier CFA mechanisms to do it.
!      Always zap the saved stack pointer value for the next frame; carrying
!      the value over from one frame to another doesn't make sense.  */
!   if (!orig_context.reg[__builtin_dwarf_sp_column ()])
!     {
!       tmp_sp = (_Unwind_Ptr) context->cfa;
!       orig_context.reg[__builtin_dwarf_sp_column ()] = &tmp_sp;
!     }
!   context->reg[__builtin_dwarf_sp_column ()] = NULL;
  
    /* Compute this frame's CFA.  */
    switch (fs->cfa_how)
*************** uw_install_context_1 (struct _Unwind_Con
*** 1201,1206 ****
--- 1207,1213 ----
  		      struct _Unwind_Context *target)
  {
    long i;
+   void *target_cfa;
  
  #if __GTHREADS
    {
*************** uw_install_context_1 (struct _Unwind_Con
*** 1222,1232 ****
  	memcpy (c, t, dwarf_reg_size_table[i]);
      }
  
    /* We adjust SP by the difference between CURRENT and TARGET's CFA.  */
    if (STACK_GROWS_DOWNWARD)
!     return target->cfa - current->cfa + target->args_size;
    else
!     return current->cfa - target->cfa - target->args_size;
  }
  
  static inline _Unwind_Ptr
--- 1229,1246 ----
  	memcpy (c, t, dwarf_reg_size_table[i]);
      }
  
+   /* If the last frame records a saved stack pointer, use it.  */
+   if (target->reg[__builtin_dwarf_sp_column ()])
+     target_cfa = (void *)(_Unwind_Ptr)
+       _Unwind_GetGR (target, __builtin_dwarf_sp_column ());
+   else
+     target_cfa = target->cfa;
+ 
    /* We adjust SP by the difference between CURRENT and TARGET's CFA.  */
    if (STACK_GROWS_DOWNWARD)
!     return target_cfa - current->cfa + target->args_size;
    else
!     return current->cfa - target_cfa - target->args_size;
  }
  
  static inline _Unwind_Ptr

-- 
  Dr. Ulrich Weigand
  weigand@informatik.uni-erlangen.de