From: Richard Henderson <rth@redhat.com>
To: Dale Johannesen <dalej@apple.com>
Cc: gcc@gcc.gnu.org
Subject: Re: how to fix anti-optimization?
Date: Fri, 14 Sep 2001 13:36:00 -0000 [thread overview]
Message-ID: <20010914133646.A15601@redhat.com> (raw)
In-Reply-To: <200109141950.f8EJoNw06758@scv2.apple.com>
On Fri, Sep 14, 2001 at 12:50:47PM -0700, Dale Johannesen wrote:
> Some problems with this. First, I discover that LEGITIMATE_CONSTANT_P on
> rs6000 accepts some FP consts, after checking to see whether they can be
> *moved* into int regs with 1 instruction per word. That's not right, is
> it?
Actually, it is. While looking at a different problem, I remembered
that x86 does the same thing, since the best way to do "x = 2.0f" is
"movl $0x35800000,x".
I think you can just forget the LEGITIMATE_CONSTANT_P check.
> For this, the RT is to load from the array for the 1st two parameters, and
> to do the multiplication at compile time, loading the resulting constant
> 15.0 from a new memory loc. So far I haven't been able to get that.
Hmm. I'd expect cse_insn to be able to handle that...
r~
next prev parent reply other threads:[~2001-09-14 13:36 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-12 11:34 dalej
2001-09-12 15:14 ` Richard Henderson
2001-09-14 12:50 ` Dale Johannesen
2001-09-14 13:02 ` David Edelsohn
2001-09-14 13:36 ` Richard Henderson [this message]
2001-09-13 10:50 ` David Edelsohn
2001-09-13 11:03 ` Dale Johannesen
2001-09-14 15:27 Richard Kenner
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