Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!usc!jarthur!uunet!taumet!steve
From: steve@taumet.com (Stephen Clamage)
Newsgroups: comp.lang.c++
Subject: Re: const Performance benefits {Was: const is not object-oriented}
Message-ID: <517@taumet.com>
Date: 18 Nov 90 00:30:25 GMT
References: <13050@cadillac.CAD.MCC.COM> <1990Nov12.184240.23430@odin.corp.sgi.com> <BILL.90Nov14133604@hcx2.ssd.csd.harris.com> <11935@life.ai.mit.edu>
Organization: Taumetric Corporation, San Diego
Lines: 16

rpk@rice-chex.ai.mit.edu (Robert Krajewski) writes:

!I'm no language innocent, but I'm not familiar with the performance
!benefits of using const.  (I'm certainly aware of the safety
!benefits.)
!The only one I could think of is that the compiler could re-order
!function calls in expressions.

It allows a number of optimization opportunities.

The major one is that unless declared extern, a const scalar type need
not be assigned to memory, and if the definition is visible the literal
value may be used instead of reading it from storage.
-- 

Steve Clamage, TauMetric Corp, steve@taumet.com