Re: Build problems on Solaris 2.5.1

[Richard Earnshaw <rearnsha at arm dot com>]

> The problem is decode_rtx_const, which tries to memset its VALUE argument.
> However, this has just been xmalloced (in record_constant_rtx) with
> 
> 
>       ptr = ((struct constant_descriptor *) 
>              xcalloc (1, 
>                       (sizeof (struct constant_descriptor) 
>                        + sizeof (struct rtx_const) - 1)));
>       decode_rtx_const (mode, x, (struct rtx_const *) ptr->contents);
> 
> Now the native compiler is optimizing the memset into two "std" 
> instructions.  Unfortunately, the pointer is only word aligned, not dword 
> aligned, so the std instruction is generating a bus error.
> 
> Now it looks to me that the code in record_constant_rtx is doing the dodgy 
> thing (since after all, it is messing around with casts), but I could be 
> wrong.  Is it reasonable to expect struct rtx_const to be dword aligned on 
> a sparc?
> 


Here's a patch

<date>  Richard Earnshaw (rearnsha@arm.com>

	* varasm.c (struct constant_descriptor): Put CONTENTS inside a
	union to make it well-aligned.  Update all uses.


Index: varasm.c
===================================================================
RCS file: /cvs/gcc/egcs/gcc/varasm.c,v
retrieving revision 1.137
diff -p -r1.137 varasm.c
*** varasm.c	2000/11/03 18:55:53	1.137
--- varasm.c	2000/11/10 15:20:55
*************** struct constant_descriptor
*** 2327,2333 ****
    struct constant_descriptor *next;
    char *label;
    rtx rtl;
!   unsigned char contents[1];
  };
  
  #define HASHBITS 30
--- 2327,2337 ----
    struct constant_descriptor *next;
    char *label;
    rtx rtl;
!   union 
!   {
!     unsigned char contents[1];
!     double algn;	/* Make sure this is well aligned.  */
!   } u;
  };
  
  #define HASHBITS 30
*************** compare_constant (exp, desc)
*** 2477,2483 ****
       tree exp;
       struct constant_descriptor *desc;
  {
!   return 0 != compare_constant_1 (exp, desc->contents);
  }
  
  /* Compare constant expression EXP with a substring P of a constant descriptor.
--- 2481,2487 ----
       tree exp;
       struct constant_descriptor *desc;
  {
!   return 0 != compare_constant_1 (exp, desc->u.contents);
  }
  
  /* Compare constant expression EXP with a substring P of a constant descriptor.
*************** compare_constant_rtx (mode, x, desc)
*** 3475,3481 ****
       rtx x;
       struct constant_descriptor *desc;
  {
!   register int *p = (int *) desc->contents;
    register int *strp;
    register int len;
    struct rtx_const value;
--- 3479,3485 ----
       rtx x;
       struct constant_descriptor *desc;
  {
!   register int *p = (int *) desc->u.contents;
    register int *strp;
    register int len;
    struct rtx_const value;
*************** record_constant_rtx (mode, x)
*** 3505,3512 ****
    ptr = ((struct constant_descriptor *) 
  	 xcalloc (1, 
  		  (sizeof (struct constant_descriptor) 
! 		   + sizeof (struct rtx_const) - 1)));
!   decode_rtx_const (mode, x, (struct rtx_const *) ptr->contents);
  
    return ptr;
  }
--- 3509,3516 ----
    ptr = ((struct constant_descriptor *) 
  	 xcalloc (1, 
  		  (sizeof (struct constant_descriptor) 
! 		   + sizeof (struct rtx_const) - sizeof (double))));
!   decode_rtx_const (mode, x, (struct rtx_const *) ptr->u.contents);
  
    return ptr;
  }