From: "Nick Roberts" <Nick.Roberts@dial.pipex.com>
Subject: Re: should I be interested in ada?
Date: 1999/02/19
Date: 1999-02-19T00:00:00+00:00 [thread overview]
Message-ID: <7aknfn$au1$1@plug.news.pipex.net> (raw)
In-Reply-To: 7ajkhb$dol$1@nnrp1.dejanews.com
robert_dewar@my-dejanews.com wrote in message
<7ajkhb$dol$1@nnrp1.dejanews.com>...
|In article <7aikfp$nhq$3@plug.news.pipex.net>,
| "Nick Roberts" <Nick.Roberts@dial.pipex.com> wrote:
|> Thus, the high-level language is, theoretically,
|> completely immaterial [to quality of fpt code]
|
|Not quite. The aliasing rules for parameters in Fortran
|are quite different from those in Ada, and clearly are
|preferable from a code generation point of view. How
|significant this is in *practice* is open to question,
|but in *theory* Fortran can sometimes produce better code.
Correct for most existing Ada and Fortran compilers. However, I do not
believe that this would be true for an Ada compiler which generates code
'late' (i.e. effectively at the linking stage).
Under alias analysis, an Ada subprogram which is never called with aliased
parameters (i.e. two or more by-reference parameters which have the same
object as actuals) can be compiled to assume the corresponding formals will
never be aliased. This assumption is useful (only) where one or both
parameters are modified, because it allows rescheduling (and sometimes other
optimisations) of the writes. 'Late code' compilers can always do this
analysis globally, and thus can always perform this potential optimisation.
I believe there is a trend, these days, for aggressively optimising
compilers to be of the 'late code' persuasion (mine will be). Of course,
admittedly, even such compilers cannot get round the problem for the
generation of a 'shared object' library (aka DLL).
On the other hand, ironically, Fortran (77 and 90) often cannot perform this
optimisation (reliably), since the language has always suffered from the
fact that not all compilers have enforced the 'no aliasing' rule, and
therefore many programs (unfortunately) have been written which take
advantage of this fact.
-------------------------------------
Nick Roberts
-------------------------------------
next prev parent reply other threads:[~1999-02-19 0:00 UTC|newest]
Thread overview: 89+ messages / expand[flat|nested] mbox.gz Atom feed top
1999-02-14 0:00 should I be interested in ada? Phillip Helbig
1999-02-15 0:00 ` Marin David Condic
1999-02-23 0:00 ` David Starner
1999-02-15 0:00 ` Gautier
1999-02-16 0:00 ` Ken Thomas
1999-02-17 0:00 ` Nick Roberts
1999-02-18 0:00 ` robert_dewar
1999-02-18 0:00 ` Nick Roberts
1999-02-18 0:00 ` robert_dewar
1999-02-19 0:00 ` Nick Roberts
1999-02-19 0:00 ` robert_dewar
1999-02-19 0:00 ` Nick Roberts
1999-02-20 0:00 ` robert_dewar
1999-02-20 0:00 ` Steve Doiel
1999-02-20 0:00 ` robert_dewar
1999-02-22 0:00 ` dennison
1999-02-22 0:00 ` Nick Roberts
1999-02-23 0:00 ` Robert I. Eachus
1999-02-24 0:00 ` White rabbit (was: should I be interested in ada?) dennison
1999-02-25 0:00 ` Alice books " JP Thornley
1999-02-25 0:00 ` Robert I. Eachus
1999-02-19 0:00 ` should I be interested in ada? William Clodius
1999-02-19 0:00 ` Phillip Helbig
1999-02-19 0:00 ` dennison
1999-02-19 0:00 ` robert_dewar
1999-02-19 0:00 ` William Clodius
1999-02-19 0:00 ` Nick Roberts
1999-02-20 0:00 ` robert_dewar
1999-02-22 0:00 ` Nick Roberts
1999-02-18 0:00 ` Jerry Petrey
1999-02-18 0:00 ` fraser
1999-02-19 0:00 ` Matthew Heaney
1999-02-20 0:00 ` fraser
1999-02-18 0:00 ` Nick Roberts
1999-02-18 0:00 ` Dan Nagle
1999-02-18 0:00 ` nabbasi
1999-02-19 0:00 ` Nick Roberts
1999-02-19 0:00 ` Dan Nagle
1999-02-19 0:00 ` robert_dewar
1999-02-19 0:00 ` Nick Roberts
1999-02-19 0:00 ` Dan Nagle
1999-02-23 0:00 ` Peter Hermann
1999-02-19 0:00 ` robert_dewar
1999-02-19 0:00 ` Nick Roberts [this message]
1999-02-19 0:00 ` William Clodius
1999-02-20 0:00 ` Nick Roberts
1999-02-21 0:00 ` robert_dewar
1999-02-21 0:00 ` William Clodius
1999-02-22 0:00 ` Nick Roberts
1999-02-19 0:00 ` robert_dewar
1999-02-21 0:00 ` William Clodius
1999-02-23 0:00 ` Robert I. Eachus
1999-02-18 0:00 ` Joel Seidman
1999-02-18 0:00 ` William Clodius
1999-02-18 0:00 ` nabbasi
1999-02-18 0:00 ` robert_dewar
1999-02-18 0:00 ` robert_dewar
1999-02-19 0:00 ` William Clodius
1999-02-19 0:00 ` Nick Roberts
1999-02-20 0:00 ` robert_dewar
1999-02-22 0:00 ` Nick Roberts
1999-02-22 0:00 ` William Clodius
1999-02-23 0:00 ` robert_dewar
1999-02-23 0:00 ` Nick Roberts
1999-02-22 0:00 ` William Clodius
1999-02-23 0:00 ` Nick Roberts
1999-02-23 0:00 ` William Clodius
1999-02-25 0:00 ` Nick Roberts
1999-02-25 0:00 ` robert_dewar
1999-02-23 0:00 ` Robert I. Eachus
1999-02-24 0:00 ` Nick Roberts
1999-02-26 0:00 ` Robert A Duff
1999-02-27 0:00 ` Semantic info pragmas (was: should I be interested in ada?) Nick Roberts
1999-03-01 0:00 ` Samuel Tardieu
1999-03-01 0:00 ` Robert A Duff
1999-02-24 0:00 ` should I be interested in ada? William Clodius
1999-02-24 0:00 ` William Clodius
1999-02-25 0:00 ` Nick Roberts
1999-02-25 0:00 ` robert_dewar
1999-02-26 0:00 ` Nick Roberts
1999-02-18 0:00 ` robert_dewar
1999-02-18 0:00 ` Nick Roberts
1999-02-18 0:00 ` William Clodius
1999-02-18 0:00 ` dennison
1999-02-20 0:00 ` Hartmut H. Schaefer
1999-02-20 0:00 ` bill
1999-02-21 0:00 ` dewar
1999-02-21 0:00 ` dewar
1999-02-22 0:00 ` dennison
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