[Bug target/15286] ICE cause by reload

[uweigand at gcc dot gnu dot org]

------- Additional Comments From uweigand at gcc dot gnu dot org  2004-10-25 20:42 -------
(My last message got messed up somehow, I'm trying again.)

David Edelsohn wrote: 
 
>Correction.  While the reload changes fix the crash, it looks like there still  
>is a bug because the resulting code does not access the correct SUBREG.  It  
>does not access the LSW. 
 
That would be because alter_subreg doesn't handle paradoxical subregs 
on big-endian machines correctly.  Something like the following (untested) 
should fix that one: 
 
Index: gcc/final.c 
=================================================================== 
RCS file: /cvs/gcc/gcc/gcc/final.c,v 
retrieving revision 1.339 
diff -c -p -r1.339 final.c 
*** gcc/final.c 22 Oct 2004 17:05:05 -0000      1.339 
--- gcc/final.c 25 Oct 2004 20:35:41 -0000 
*************** alter_subreg (rtx *xp) 
*** 2607,2613 **** 
    /* simplify_subreg does not remove subreg from volatile references. 
       We are required to.  */ 
    if (MEM_P (y)) 
!     *xp = adjust_address (y, GET_MODE (x), SUBREG_BYTE (x)); 
    else 
      { 
        rtx new = simplify_subreg (GET_MODE (x), y, GET_MODE (y), 
--- 2607,2628 ---- 
    /* simplify_subreg does not remove subreg from volatile references. 
       We are required to.  */ 
    if (MEM_P (y)) 
!     { 
!       int offset = SUBREG_BYTE (x); 
! 
!       /* For paradoxical subregs on big-endian machines, SUBREG_BYTE 
!        contains 0 instead of the proper offset.  See simplify_subreg.  */ 
!       if (offset == 0 && GET_MODE_SIZE (y) < GET_MODE_SIZE (x)) 
!         { 
!           int difference = GET_MODE_SIZE (y) - GET_MODE_SIZE (x); 
!           if (WORDS_BIG_ENDIAN) 
!             offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD; 
!           if (BYTES_BIG_ENDIAN) 
!             offset += difference % UNITS_PER_WORD; 
!         } 
! 
!       *xp = adjust_address (y, GET_MODE (x), offset); 
!     } 
    else 
      { 
        rtx new = simplify_subreg (GET_MODE (x), y, GET_MODE (y), 
 
 

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15286