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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/51933] [4.7 regression] wrong code due to -free Date: Sun, 22 Jan 2012 10:35:00 -0000 [thread overview] Message-ID: <bug-51933-4-us2WE99Nxt@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-51933-4@http.gcc.gnu.org/bugzilla/> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51933 --- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-01-22 09:42:05 UTC --- Created attachment 26410 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26410 gcc47-pr51933.patch Patch I wrote last night. Passed bootstrap/regtest, the only cases where it prevented something was in the new testcase and in jcf-parse.c (rewrite_reflection_indexes) with -m64, where it fixed an miscompilation. What happened there is that some earlier bb (but in a loop) was doing a SImode->DImode zero extension, and later in the loop there was a SImode ior, followed by HImode->SImode zero extension of that, which fed the earlier SImode->DImode zero extension. The SImode->DImode insn was processed first, removed and changed the HImode->SImode zero extension into HImode->DImode zero extension. But as the HImode->SImode extension was changed, its df links were gone. When the HImode-> zero extension is later processed as candidate, get_defs returns NULL and we assume all the dependencies have been adjusted. Which leads me to thinking that this patch is a wrong approach, and perhaps we should instead DF_DEFER_INSN_RESCAN in ree.c and adjust, so that we can cope with the adjusted insns.
next prev parent reply other threads:[~2012-01-22 9:42 UTC|newest] Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-01-21 14:43 [Bug rtl-optimization/51933] New: [4.7 Regression] Wrong-code " jakub at gcc dot gnu.org 2012-01-21 15:00 ` [Bug rtl-optimization/51933] " jakub at gcc dot gnu.org 2012-01-21 15:51 ` jakub at gcc dot gnu.org 2012-01-21 16:05 ` ebotcazou at gcc dot gnu.org 2012-01-21 16:12 ` [Bug rtl-optimization/51933] [4.7 regression] wrong code " jakub at gcc dot gnu.org 2012-01-21 19:57 ` jakub at gcc dot gnu.org 2012-01-21 22:01 ` ebotcazou at gcc dot gnu.org 2012-01-22 10:35 ` jakub at gcc dot gnu.org [this message] 2012-01-22 19:38 ` jakub at gcc dot gnu.org 2012-01-23 9:42 ` jakub at gcc dot gnu.org 2012-01-23 9:42 ` jakub at gcc dot gnu.org
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