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From: "marcel.kyas@fu-berlin.de" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug c/53416] New: 4.7.0 Wrong code when optimising loop involving _rdrand32_step Date: Sat, 19 May 2012 17:15:00 -0000 [thread overview] Message-ID: <bug-53416-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53416 Bug #: 53416 Summary: 4.7.0 Wrong code when optimising loop involving _rdrand32_step Classification: Unclassified Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: c AssignedTo: unassigned@gcc.gnu.org ReportedBy: marcel.kyas@fu-berlin.de Created attachment 27440 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27440 Reduced test case The attached file prints different output depending whether it is compiled with -O0, -O1 or -O2 on gcc-Version 4.7.0 20120507 (Red Hat 4.7.0-5) (GCC). When the file is built with gcc -std=c99 -mrdrnd -O0 rngtest.i, it prints four different random numbers. If it is built with gcc -std=c99 -mrdrnd -O1 rngtest.i, it prints the same number four times. If it is built with gcc -std=c99 -mrdrnd -O2 rngtest.i, it prints the random number four times and prints the random number as the result of the call to _rdrand32_step. The last one is especially surprising, because _rdrand32_step should only return 0 or 1.
next reply other threads:[~2012-05-19 14:56 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-05-19 17:15 marcel.kyas@fu-berlin.de [this message] 2012-05-20 17:48 ` [Bug target/53416] " hjl.tools at gmail dot com 2012-05-20 18:22 ` hjl.tools at gmail dot com 2012-05-21 12:41 ` hjl at gcc dot gnu.org 2012-05-21 13:07 ` hjl at gcc dot gnu.org 2012-05-21 13:09 ` hjl at gcc dot gnu.org 2012-05-21 13:10 ` hjl.tools at gmail dot com
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