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* [Bug libgcc/61662] New: Incorrect value calculated for _lrotl on LLP64 systems @ 2014-07-01 7:06 gccbugzilla at limegreensocks dot com 2014-07-01 22:43 ` [Bug target/61662] " hjl.tools at gmail dot com ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: gccbugzilla at limegreensocks dot com @ 2014-07-01 7:06 UTC (permalink / raw) To: gcc-bugs 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug target/61662] Incorrect value calculated for _lrotl on LLP64 systems 2014-07-01 7:06 [Bug libgcc/61662] New: Incorrect value calculated for _lrotl on LLP64 systems gccbugzilla at limegreensocks dot com @ 2014-07-01 22:43 ` hjl.tools at gmail dot com 2014-07-15 17:14 ` gccbugzilla at limegreensocks dot com ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: hjl.tools at gmail dot com @ 2014-07-01 22:43 UTC (permalink / raw) To: gcc-bugs 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. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug target/61662] Incorrect value calculated for _lrotl on LLP64 systems 2014-07-01 7:06 [Bug libgcc/61662] New: Incorrect value calculated for _lrotl on LLP64 systems gccbugzilla at limegreensocks dot com 2014-07-01 22:43 ` [Bug target/61662] " hjl.tools at gmail dot com @ 2014-07-15 17:14 ` gccbugzilla at limegreensocks dot com 2014-07-16 22:02 ` gerald at gcc dot gnu.org 2014-07-16 22:03 ` gerald at pfeifer dot com 3 siblings, 0 replies; 5+ messages in thread From: gccbugzilla at limegreensocks dot com @ 2014-07-15 17:14 UTC (permalink / raw) To: gcc-bugs 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug target/61662] Incorrect value calculated for _lrotl on LLP64 systems 2014-07-01 7:06 [Bug libgcc/61662] New: Incorrect value calculated for _lrotl on LLP64 systems gccbugzilla at limegreensocks dot com 2014-07-01 22:43 ` [Bug target/61662] " hjl.tools at gmail dot com 2014-07-15 17:14 ` gccbugzilla at limegreensocks dot com @ 2014-07-16 22:02 ` gerald at gcc dot gnu.org 2014-07-16 22:03 ` gerald at pfeifer dot com 3 siblings, 0 replies; 5+ messages in thread From: gerald at gcc dot gnu.org @ 2014-07-16 22:02 UTC (permalink / raw) To: gcc-bugs 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 ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug target/61662] Incorrect value calculated for _lrotl on LLP64 systems 2014-07-01 7:06 [Bug libgcc/61662] New: Incorrect value calculated for _lrotl on LLP64 systems gccbugzilla at limegreensocks dot com ` (2 preceding siblings ...) 2014-07-16 22:02 ` gerald at gcc dot gnu.org @ 2014-07-16 22:03 ` gerald at pfeifer dot com 3 siblings, 0 replies; 5+ messages in thread From: gerald at pfeifer dot com @ 2014-07-16 22:03 UTC (permalink / raw) To: gcc-bugs 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! ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2014-07-16 22:03 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2014-07-01 7:06 [Bug libgcc/61662] New: Incorrect value calculated for _lrotl on LLP64 systems gccbugzilla at limegreensocks dot com 2014-07-01 22:43 ` [Bug target/61662] " hjl.tools at gmail dot com 2014-07-15 17:14 ` gccbugzilla at limegreensocks dot com 2014-07-16 22:02 ` gerald at gcc dot gnu.org 2014-07-16 22:03 ` gerald at pfeifer dot com
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