From: Segher Boessenkool <segher@kernel.crashing.org>
To: Bernd Schmidt <bschmidt@redhat.com>
Cc: Richard Biener <richard.guenther@gmail.com>,
Michael Meissner <meissner@linux.vnet.ibm.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
David Edelsohn <dje.gcc@gmail.com>,
Bill Schmidt <wschmidt@linux.vnet.ibm.com>
Subject: Re: [PATCH], PowerPC support to enable -mlra and/or -mfloat128
Date: Tue, 12 Jul 2016 16:31:00 -0000 [thread overview]
Message-ID: <20160712163134.GH13551@gate.crashing.org> (raw)
In-Reply-To: <0c9127b4-5320-a5be-b9fd-2c50451b34c3@redhat.com>
On Tue, Jul 12, 2016 at 05:17:04PM +0200, Bernd Schmidt wrote:
> The Blackfin thing happens frequently with -fomit-frame-pointer when we have
>
> (insn 66 64 70 8 (set (reg:SI 96 [ ivtmp.32 ])
> (reg/f:SI 15 FP)) 19 {*movsi_insn}
>
> Which LRA transforms to an invalid insn:
>
> (insn 66 64 70 8 (set (reg:SI 15 FP [orig:96 ivtmp.32 ] [96])
> (plus:SI (reg/f:SI 14 SP)
> (const_int 4 [0x4]))) 50 {addsi3}
> (expr_list:REG_EQUAL (reg/f:SI 15 FP)
> (nil)))
>
> Haven't fully debugged it but it looks like an instance of the same
> problem: not using the correct register numbers in elimination. An FP+FP
> addition would be fine (which is how I'm guessing we arrived at this
> pattern), but once you substitute the real register number you get an
> invalid insn. So LRA is somewhat defective in this area.
Do you have a testcase? This sounds like fun :-)
Segher
next prev parent reply other threads:[~2016-07-12 16:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-11 20:07 Michael Meissner
2016-07-11 21:25 ` Michael Meissner
2016-07-20 17:04 ` [PATCH #2], " Michael Meissner
2016-07-12 10:29 ` [PATCH], " Richard Biener
2016-07-12 11:19 ` Segher Boessenkool
2016-07-12 11:21 ` Bernd Schmidt
2016-07-12 11:31 ` Richard Biener
2016-07-12 12:16 ` Segher Boessenkool
2016-07-12 12:40 ` Bernd Schmidt
2016-07-12 12:45 ` Segher Boessenkool
2016-07-12 12:48 ` Bernd Schmidt
2016-07-12 15:17 ` Bernd Schmidt
2016-07-12 16:31 ` Segher Boessenkool [this message]
2016-07-12 16:57 ` Bernd Schmidt
2016-07-12 12:55 ` Segher Boessenkool
2016-07-12 19:44 ` Michael Meissner
2016-07-12 21:20 ` Segher Boessenkool
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