From: Ian Lance Taylor <ian@airs.com>
To: fjahanian@apple.com
Cc: Dale Johannesen <dalej@apple.com>, gcc mailing list <gcc@gcc.gnu.org>
Subject: Re: Fwd: [RFC] - Regression exposed by recent change to compress_float_constant
Date: Fri, 19 Aug 2005 23:08:00 -0000 [thread overview]
Message-ID: <m3br3t4ja0.fsf@gossamer.airs.com> (raw)
In-Reply-To: <263482fcfbcc31184df9e901a9811db9@apple.com>
On Aug 10, 2005, at 12:43 PM, Fariborz Jahanian wrote:
> + /* APPLE LOCAL begin radar 4153339 */
> + if (n_sets == 1 && GET_CODE (sets[i].src) == REG
> + && src_const && GET_CODE (src_const) == CONST_DOUBLE)
> + {
> + src_folded = src_const;
> + src_folded_cost = src_folded_regcost = -1;
> + }
> + /* APPLE LOCAL end radar 4153339 */
I don't see how this could be right for FSF gcc. It's putting a
target specific decision into the target independent code. It is
simply not true that a constant double is always cheaper than a
register, for example. The similar case you cite, of the indirect
jump insn, really is target independent--a branch to a known
destination is always going to be cheaper than an indirect branch via
a register.
It seems possible that this could be fixed by adjusting the cost of
the CONST_DOUBLE in the target backend.
Ian
prev parent reply other threads:[~2005-08-19 23:08 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-08-19 22:53 Dale Johannesen
2005-08-19 23:08 ` Ian Lance Taylor [this message]
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