From: kenner@vlsi1.ultra.nyu.edu (Richard Kenner)
To: dalej@apple.com
Cc: gcc@gcc.gnu.org
Subject: Re: how to fix anti-optimization?
Date: Fri, 14 Sep 2001 15:27:00 -0000 [thread overview]
Message-ID: <10109142233.AA00201@vlsi1.ultra.nyu.edu> (raw)
const double Prescale[] = { 3.0, 5.0 };
extern void bar(double, double);
void foo () { bar(Prescale[0], Prescale[1]); }
With -O1 or higher, gcc substitutes constants 3.0 and 5.0 for the array
references. This isn't a win on targets where the extra copies of these
constants have to go in memory; you get an extra copy of the constants in
data space.
Only if it's no more complex an expression. Consider Prescale[0]*Prescale[1].
It's *much* faster to do the folding in that case.
next reply other threads:[~2001-09-14 15:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-14 15:27 Richard Kenner [this message]
-- strict thread matches above, loose matches on Subject: below --
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
2001-09-13 10:50 ` David Edelsohn
2001-09-13 11:03 ` Dale Johannesen
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