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From: "olegendo at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/53949] [SH] Add support for mac.w / mac.l instructions
Date: Fri, 13 Jul 2012 10:34:00 -0000 [thread overview]
Message-ID: <bug-53949-4-PzEDHdpq5Q@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-53949-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53949
--- Comment #1 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-07-13 10:34:20 UTC ---
(In reply to comment #0)
> So far, GCC does not utilize the integer multiply-add instructions.
> On SH1 only the mac.w instruction is supported.
> On SH2 and above the mac.w and mac.l instructions are available.
>
> Carry over from PR 39423 comment #20
>
> > On a related thread, for further work, I'm thinking on adding support for the
> > MAC instruction, now that was have the multiply and add. But this requires
> > exposing the MACLH registers to reload. Had anyone had a thought on this ? I'd
> > like to give this a try pretty soon.
I think the biggest problem is that the mac operands have to be in memory.
For example:
long long fun (int a, int long b, long long c)
{
return (long long)a * (long long)b + c;
}
would need to become something like ...
mov.l r4,@-r15
mov r15,r1
mov.l r5,@-r15
lds r6,mach
lds r7,macl
mac.l @r15+,@r1+
sts mach,r1
sts macl,r0
rts
add #4,r15
not using the mac instruction seems a bit simpler in this case:
dmuls.l r4,r5
sts mach,r1
clrt
sts macl,r0
addc r6,r0
rts
addc r7,r1
I think the mac instructions can be very useful when they can be used inside of
loops, but for this the whole post-inc memory stuff has to integrate properly
into
the surrounding code.
Chris, do you have any ideas/plans on how to handle the SR.S bit, for example
to implement
the ssmaddhisi4 pattern with mac.w?
next prev parent reply other threads:[~2012-07-13 10:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-13 9:01 [Bug target/53949] New: " olegendo at gcc dot gnu.org
2012-07-13 10:34 ` olegendo at gcc dot gnu.org [this message]
2012-07-13 11:01 ` [Bug target/53949] " chrbr at gcc dot gnu.org
2012-07-13 11:24 ` chrbr at gcc dot gnu.org
2012-07-15 12:11 ` olegendo at gcc dot gnu.org
2012-07-17 19:13 ` olegendo at gcc dot gnu.org
2012-07-17 23:05 ` kkojima at gcc dot gnu.org
2012-07-22 16:47 ` olegendo at gcc dot gnu.org
2012-10-11 20:43 ` olegendo at gcc dot gnu.org
2012-11-07 21:31 ` olegendo at gcc dot gnu.org
2013-05-04 13:39 ` olegendo at gcc dot gnu.org
2013-12-17 12:25 ` olegendo at gcc dot gnu.org
2013-12-17 12:37 ` olegendo at gcc dot gnu.org
2015-01-30 19:37 ` olegendo at gcc dot gnu.org
2015-02-01 0:37 ` olegendo at gcc dot gnu.org
2015-04-08 20:08 ` olegendo at gcc dot gnu.org
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