[Bug libgcc/61662] New: Incorrect value calculated for _lrotl on LLP64 systems

[Bug libgcc/61662] New: Incorrect value calculated for _lrotl on LLP64 systems

[gccbugzilla at limegreensocks dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61662

            Bug ID: 61662
           Summary: Incorrect value calculated for _lrotl on LLP64 systems
           Product: gcc
           Version: 4.10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgcc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gccbugzilla at limegreensocks dot com

Created attachment 33037
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=33037&action=edit
Proposed patch

There is a problem in ia32intrin.h.  Extracting bits of the code to highlight
the problem, we get:

#ifdef __x86_64__
#define _lrotl(a,b)        __rolq((a), (b)) // rotate left qword
#else
#define _lrotl(a,b)        __rold((a), (b)) // rotate left dword
#endif

This works correctly for linux, since on linux, longs use 8 bytes on 64bit and
4 bytes on 32bit (aka LP64).  However, in native Windows, longs are 4 bytes for
both (aka LLP64).  

So on 64bit Windows, 4 byte longs get promoted to a qword, bits get rotated
into the upper bytes, then get truncated when cast back into a 4 byte long. 
Oops.

The problem here is that using "#ifdef __x86_64__" to determine the size of a
long does not reliably yield the correct result.

While gcc provides a define named __SIZEOF_LONG__, it doesn't seem like this is
used very often outside of the testsuite.  Therefore the proposed patch
(attached) uses the __LP64__ define.

Testcase:

   printf("sizeof(long): %d sizeof(ptr): %d "
          "_lrotl(0x80000000,1): 0x%lx _lrotr(1,1): 0x%lx\n", 
      sizeof(long), sizeof(void *), _lrotl(0x80000000, 1), _lrotr(1,1));

64bit Windows yields:

sizeof(long): 4 sizeof(ptr): 8 _lrotl(0x80000000,1): 0x0 _lrotr(1,1): 0x0

Applying the patch yields:

sizeof(long): 4 sizeof(ptr): 8 _lrotl(0x80000000,1): 0x1 _lrotr(1,1):
0x80000000

[Bug target/61662] Incorrect value calculated for _lrotl on LLP64 systems

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61662

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-07-01
                 CC|                            |hjl.tools at gmail dot com
          Component|libgcc                      |target
     Ever confirmed|0                           |1

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
Please send the patch to the gcc-patches mailing list. Thanks.

[Bug target/61662] Incorrect value calculated for _lrotl on LLP64 systems

[gccbugzilla at limegreensocks dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61662

--- Comment #2 from David <gccbugzilla at limegreensocks dot com> ---
Sent July 9, 2014: https://gcc.gnu.org/ml/gcc-patches/2014-07/msg00604.html

[Bug target/61662] Incorrect value calculated for _lrotl on LLP64 systems

[gerald at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61662

--- Comment #3 from gerald at gcc dot gnu.org <gerald at gcc dot gnu.org> ---
Author: gerald
Date: Wed Jul 16 22:01:41 2014
New Revision: 212699

URL: https://gcc.gnu.org/viewcvs?rev=212699&root=gcc&view=rev
Log:
    PR target/61662
    * config/i386/ia32intrin.h: Use __LP64__ to determine size of long.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/i386/ia32intrin.h

[Bug target/61662] Incorrect value calculated for _lrotl on LLP64 systems

[gerald at pfeifer dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61662

Gerald Pfeifer <gerald at pfeifer dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |gerald at pfeifer dot com
         Resolution|---                         |FIXED

--- Comment #4 from Gerald Pfeifer <gerald at pfeifer dot com> ---
I committed a minor variation (no code changes) of this patch.

Thanks, David!