public inbox for gcc-bugs@sourceware.org help / color / mirror / Atom feed
From: "ktkachov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/42575] arm-eabi-gcc 64-bit multiply weirdness Date: Mon, 17 Nov 2014 16:23:00 -0000 [thread overview] Message-ID: <bug-42575-4-yRggJgf8EK@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-42575-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=42575 ktkachov at gcc dot gnu.org changed: What |Removed |Added ---------------------------------------------------------------------------- Status|RESOLVED |REOPENED Resolution|FIXED |--- --- Comment #13 from ktkachov at gcc dot gnu.org --- So I see this regression still, but only for some -mcpu options. For example for -mcpu=cortex-a15 we get: mul r3, r0, r3 strd r4, [sp, #-8]! umull r4, r5, r0, r2 mla r1, r2, r1, r3 mov r0, r4 add r5, r1, r5 mov r1, r5 ldrd r4, [sp] add sp, sp, #8 whereas for cortex-a7 we get: mul r3, r0, r3 mla r3, r2, r1, r3 umull r0, r1, r0, r2 add r1, r3, r1 I think the problem here is reload. If I look at the the dump of postreload, for the 'bad' RTL I see: r0(SI) := r0(SI) r3(SI) := r0(SI) * r3(SI) r4(DI) := r0(SI) * r2(SI) //with sign extension r1(SI) := r2(SI) * r1(SI) + r3(SI) r5(SI) := r1(SI) + r5(SI) r0(DI) := r4(DI) whereas for the good one I see: r0(SI) := r0(SI) r3(SI) := r0(SI) * r3(SI) r3(SI) := r2(SI) * r1(SI) + r3(SI) r0(DI) := r0(SI) * r2(SI) //with sign extension r1(SI) := r3(SI) + r1(SI) r0(DI) := r0(DI) In the good one the final insn is eliminated due to being dead, whereas the in the bad one the final DImode move is split into two moves. Sched1 changed the order of the mult and mult-accumulate but it's the register allocator that causes the bad codegen
next prev parent reply other threads:[~2014-11-17 16:23 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <bug-42575-4@http.gcc.gnu.org/bugzilla/> 2011-09-20 20:54 ` jules at gcc dot gnu.org 2013-05-29 9:55 ` ktkachov at gcc dot gnu.org 2014-02-14 7:44 ` bernd.edlinger at hotmail dot de 2014-02-14 7:47 ` bernd.edlinger at hotmail dot de 2014-11-17 16:23 ` ktkachov at gcc dot gnu.org [this message] 2015-02-12 14:40 ` ktkachov at gcc dot gnu.org 2015-03-26 16:14 ` ktkachov at gcc dot gnu.org 2010-01-01 17:33 [Bug c/42575] New: arm-eabi-gcc 4.2.1 " sliao at google dot com 2010-01-04 10:54 ` [Bug rtl-optimization/42575] arm-eabi-gcc " ramana at gcc dot gnu dot org 2010-02-08 10:47 ` steven at gcc dot gnu dot org 2010-02-08 10:52 ` steven at gcc dot gnu dot org 2010-02-22 21:06 ` drow at gcc dot gnu dot org 2010-07-29 12:40 ` bernds at gcc dot gnu dot org 2010-08-18 10:34 ` mkuvyrkov at gcc dot gnu dot org 2010-08-18 10:43 ` mkuvyrkov at gcc dot gnu dot org
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=bug-42575-4-yRggJgf8EK@http.gcc.gnu.org/bugzilla/ \ --to=gcc-bugzilla@gcc.gnu.org \ --cc=gcc-bugs@gcc.gnu.org \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).