From: Ian Lance Taylor <iant@google.com>
To: Gidi Nave <gidi.nave.1@gmail.com>
Cc: gcc@gcc.gnu.org
Subject: Re: Plus Reload
Date: Tue, 11 Jan 2011 14:31:00 -0000 [thread overview]
Message-ID: <mcry66r5x7k.fsf@google.com> (raw)
In-Reply-To: <AANLkTik2wJirOgyQ+ophpOhH-hjSv3K3Xj4DPrPk545v@mail.gmail.com> (Gidi Nave's message of "Tue, 11 Jan 2011 15:30:43 +0200")
Gidi Nave <gidi.nave.1@gmail.com> writes:
> I have a question regarding Plus reload situation I ran into in my
> port (which was taken from branch 4.6):
>
> I got the following insn: Set d1 (plus r1 -96).
> d1 and r1 are 2 registers from different classes.
>
> The reload (which take place at: reload1.c , gen_reload(out = d1, in =
> (plus r1 -96)) try 3 options:
>
> 1. switch the plus operands:
> set d1 (plus -96 r1)
>
> 2. split into 2 insns - reload the const to d1 and then add r1:
> set d1 -96
> set d1 (plus d1 r1)
>
> 3. split into 2 insns - copy r1 to d1 and then add the const:
> set d1 r1
> set d1 (plus d1 -96)
>
> GCC tries generating the 1st option - and fails since no valid pattern is found.
> Then it tries generating the 2nd option and fails once again, since no
> valid pattern is found.
> Then it tries generating the 3rd option without constraint validity
> check(emit_insn_if_valid_for_reload) like the first 2 attempts,
> and creates a new insn which will later fail since it's not satisfying
> it's constraints.
>
> My question is: why is GCC certain that one of those 3 attempts must work?
> In my case, all 3 resulted insns are not supported by the architecture.
What instructions are supported by your processor here?
Ian
next prev parent reply other threads:[~2011-01-11 14:31 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-11 13:30 Gidi Nave
2011-01-11 14:31 ` Ian Lance Taylor [this message]
2011-01-11 14:59 ` Gidi Nave
2011-01-11 15:02 ` Gidi Nave
2011-01-11 15:34 ` Ian Lance Taylor
2011-01-11 16:03 ` Gidi Nave
2011-01-11 17:22 ` Ian Lance Taylor
2011-01-12 6:04 ` Gidi Nave
2011-01-12 6:28 ` Ian Lance Taylor
2011-01-12 8:45 ` Gidi Nave
2011-01-12 13:50 ` Jeff Law
2011-01-12 14:23 ` Gidi Nave
2011-01-12 16:11 ` Dave Korn
2011-01-16 8:42 ` Gidi Nave
2011-01-11 15:34 ` Jeff Law
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