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From: "rearnsha at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug target/63408] [4.8 regression] GCC emits incorrect FMA instruction on Cortex-M4 target Date: Tue, 30 Sep 2014 10:21:00 -0000 [thread overview] Message-ID: <bug-63408-4-OugfPFkSkp@http.gcc.gnu.org/bugzilla/> (raw) In-Reply-To: <bug-63408-4@http.gcc.gnu.org/bugzilla/> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63408 Richard Earnshaw <rearnsha at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |NEW Last reconfirmed| |2014-09-30 CC| |ramana at gcc dot gnu.org Summary|GCC emits incorrect FMA |[4.8 regression] GCC emits |instruction on Cortex-M4 |incorrect FMA instruction |target |on Cortex-M4 target Ever confirmed|0 |1 --- Comment #3 from Richard Earnshaw <rearnsha at gcc dot gnu.org> --- Confirmed. The compiler thinks (incorrectly) that the conversion of b to float can be merged with the negation by using the fixed-to-float conversion operation in the back-end. That is, it thinks (insn 10 9 11 2 (set (reg:SF 121 [ D.4093 ]) (mult:SF (float:SF (reg:SI 0 r0 [ b ])) (const_double:SF -4.656612873077392578125e-10 [-0x0.8p-30]))) is a legitimate instruction. vfp3_const_double_for_fract_bits() needs to be made aware that negative values cannot be used in this context. This is almost certainly a regression since the pattern was added.
next prev parent reply other threads:[~2014-09-30 10:21 UTC|newest] Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <bug-63408-4@http.gcc.gnu.org/bugzilla/> 2014-09-29 18:21 ` [Bug target/63408] " pinskia at gcc dot gnu.org 2014-09-29 19:22 ` itay at phobotic dot com 2014-09-30 10:21 ` rearnsha at gcc dot gnu.org [this message] 2014-11-19 13:28 ` [Bug target/63408] [4.8 regression] GCC emits incorrect fixed->fp conversion " rguenth at gcc dot gnu.org 2014-12-10 13:11 ` [Bug target/63408] [4.8/4.9/5 " rguenth at gcc dot gnu.org 2014-12-19 13:35 ` jakub at gcc dot gnu.org 2015-01-20 9:31 ` ramana at gcc dot gnu.org 2015-06-21 14:55 ` [Bug target/63408] [4.8/4.9/5/6 " itay at phobotic dot com 2015-06-23 8:16 ` rguenth at gcc dot gnu.org 2015-06-23 11:19 ` [Bug target/63408] [4.9/5/6 " ramana at gcc dot gnu.org 2015-06-23 12:57 ` itay at phobotic dot com 2015-06-23 13:48 ` ramana at gcc dot gnu.org 2015-06-23 16:16 ` ramana at gcc dot gnu.org 2015-06-24 8:28 ` ramana at gcc dot gnu.org 2015-06-25 8:36 ` ramana at gcc dot gnu.org 2015-06-26 20:03 ` jakub at gcc dot gnu.org 2015-06-26 20:33 ` jakub at gcc dot gnu.org 2015-07-01 8:02 ` ramana at gcc dot gnu.org
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