Re: target/7533: gcc 3.0.2 h8300 right shift 15 is wrong

Re: target/7533: gcc 3.0.2 h8300 right shift 15 is wrong

[Dick Wesseling]

The following reply was made to PR target/7533; it has been noted by GNATS.

From: Dick Wesseling <ftu@fi.uu.nl>
To: gcc-gnats@gcc.gnu.org, nobody@gcc.gnu.org
Cc:  
Subject: Re: target/7533: gcc 3.0.2 h8300 right shift 15 is wrong 
Date: Thu, 08 Aug 2002 02:32:26 +0200

 This is a multipart MIME message.
 
 --==_Exmh_-7999550880
 Content-Type: text/plain; charset=us-ascii
 
 I hate to admit this, but I was a bit too trigger-happy with my patch. 
 That 'r' should have been a 'T'. Here is the correct patch
 
 
 
 --==_Exmh_-7999550880
 Content-Type: text/plain ; name="h8300-gcc-3.0.2-patch"; charset=us-ascii
 Content-Description: h8300-gcc-3.0.2-patch
 Content-Transfer-Encoding: quoted-printable
 
 *** gcc-3.0.2/gcc/config/h8300/h8300.c.orig	Wed Nov 21 18:09:08 2001
 --- gcc-3.0.2/gcc/config/h8300/h8300.c	Thu Aug  8 01:48:15 2002
 ***************
 *** 2477,2487 ****
   	    {
   	    case SHIFT_ASHIFT:
   	      info->special =3D "shlr.w\t%e0\n\tmov.w\t%f0,%e0\n\txor.w\t%f0,%=
 f0\n\trotxr.l\t%S0";
   	      goto end;
   	    case SHIFT_LSHIFTRT:
 ! 	      info->special =3D "shll.w\t%e0\n\tmov.w\t%e0,%f0\n\txor.w\t%e0,%=
 e0\n\trotxl.l\t%S0";
   	      goto end;
   	    }
   	}
         else if ((TARGET_H8300 && count =3D=3D 16)
   	       || (TARGET_H8300H && 16 <=3D count && count <=3D 19)
 --- 2477,2487 ----
   	    {
   	    case SHIFT_ASHIFT:
   	      info->special =3D "shlr.w\t%e0\n\tmov.w\t%f0,%e0\n\txor.w\t%f0,%=
 f0\n\trotxr.l\t%S0";
   	      goto end;
   	    case SHIFT_LSHIFTRT:
 ! 	      info->special =3D "shll.w\t%T0\n\tmov.w\t%e0,%f0\n\txor.w\t%e0,%=
 e0\n\trotxl.l\t%S0";
   	      goto end;
   	    }
   	}
         else if ((TARGET_H8300 && count =3D=3D 16)
   	       || (TARGET_H8300H && 16 <=3D count && count <=3D 19)
 
 --==_Exmh_-7999550880--
 
 

Re: target/7533: gcc 3.0.2 h8300 right shift 15 is wrong

[kazu]

Synopsis: gcc 3.0.2 h8300 right shift 15 is wrong

Responsible-Changed-From-To: unassigned->kazu
Responsible-Changed-By: kazu
Responsible-Changed-When: Thu Nov  7 05:58:20 2002
Responsible-Changed-Why:
    .
State-Changed-From-To: open->closed
State-Changed-By: kazu
State-Changed-When: Thu Nov  7 05:58:20 2002
State-Changed-Why:
    Fixed in 3.3.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7533

target/7533: gcc 3.0.2 h8300 right shift 15 is wrong

[ftu]

>Number:         7533
>Category:       target
>Synopsis:       gcc 3.0.2 h8300 right shift 15 is wrong
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          wrong-code
>Submitter-Id:   net
>Arrival-Date:   Wed Aug 07 16:36:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     dick wesseling
>Release:        3.0.2
>Organization:
>Environment:
h8300 cross compiler
>Description:
The h8300 backend attempts to decompose unsigned >>15 into:

 1) a single half register left shift, which moves 1 bit into the carry
    register,

 2) followed by half register MOV and XOR which has the effect of >>16

 3) followed by a single bit full register left rotate which combines
    the carry and the register.


The bug is that step 1) uses the wrong register half.

consider the following code:

unsigned long s15(unsigned long in)  {
        return in>>15;
}

if the input parameter is EeeeeeeeeeeeeeeeRxxxxxxxxxxxxxxx 
then the following happens:

;       GCC For the Hitachi H8/300
;       By Hitachi America Ltd and Cygnus Support
; -O2

        .h8300s
        .file   "h8300-shift-bug.c"
        .section .text
        .align 1
        .global _s15
_s15:                       Carry  e0              r0
        push.l  er6
        mov.l   er7,er6         -  EeeeeeeeeeeeeeeeRxxxxxxxxxxxxxxx
> >      shll.w  e0              E  eeeeeeeeeeeeeee0Rxxxxxxxxxxxxxxx
        mov.w   e0,r0           E  eeeeeeeeeeeeeee0eeeeeeeeeeeeeee0
        xor.w   e0,e0           E  0000000000000000eeeeeeeeeeeeeee0
        rotxl.l er0             0  0000000000000000eeeeeeeeeeeeeeeE
        pop.l   er6
        rts
        .end
        .ident
"GCC: (GNU) 3.0.2"

The intended code was:

        push.l  er6         Carry  e0              r0
        mov.l   er7,er6         -  EeeeeeeeeeeeeeeeRrrrrrrrrrrrrrrr
> >      shll.w  r0              R  Eeeeeeeeeeeeeeeerrrrrrrrrrrrrrr0
        mov.w   e0,r0           R  EeeeeeeeeeeeeeeeEeeeeeeeeeeeeeee
        xor.w   e0,e0           R  0000000000000000Eeeeeeeeeeeeeeee
        rotxl.l er0             -  000000000000000EeeeeeeeeeeeeeeeR
        
>How-To-Repeat:
compile this function:
unsigned long s15(unsigned long in)  {
        return in>>15;
}
>Fix:
*** gcc-3.0.2/gcc/config/h8300/h8300.c.orig     Wed Nov 21 18:09:08 2001
--- gcc-3.0.2/gcc/config/h8300/h8300.c  Thu Aug  8 00:55:36 2002
***************
*** 2477,2487 ****
            {
            case SHIFT_ASHIFT:
              info->special = "shlr.w\t%e0\n\tmov.w\t%f0,%e0\n\txor.w\t%f0,%f0\n\trotxr.l\t%S0";
              goto end;
            case SHIFT_LSHIFTRT:
!             info->special = "shll.w\t%e0\n\tmov.w\t%e0,%f0\n\txor.w\t%e0,%e0\n\trotxl.l\t%S0";
              goto end;
            }
        }
        else if ((TARGET_H8300 && count == 16)
               || (TARGET_H8300H && 16 <= count && count <= 19)
--- 2477,2487 ----
            {
            case SHIFT_ASHIFT:
              info->special = "shlr.w\t%e0\n\tmov.w\t%f0,%e0\n\txor.w\t%f0,%f0\n\trotxr.l\t%S0";
              goto end;
            case SHIFT_LSHIFTRT:
!             info->special = "shll.w\t%r0\n\tmov.w\t%e0,%f0\n\txor.w\t%e0,%e0\n\trotxl.l\t%S0";
              goto end;
            }
        }
        else if ((TARGET_H8300 && count == 16)
               || (TARGET_H8300H && 16 <= count && count <= 19)
>Release-Note:
>Audit-Trail:
>Unformatted: