RE: optimization issue about -O2 and -Os

["Dave Korn" <dk at artimi dot com>]

> -----Original Message-----
> From: gcc-owner On Behalf Of Zack Weinberg
> Sent: 30 April 2004 16:32

> "Dave Korn" <dk@artimi.com> writes:
> 
> >   Use -fverbose-asm in conjunction with --save-temps to get 
> a list of the
> > optimisations in effect at the top of each assembler code 
> file.  Try it with
> > -Os and -O2, and note the differences between them.  You 
> may be able to
> > narrow it down to a specific -f flag by starting with -O2 
> and introducing
> > the changes between that and -Os one at a time. 
> 
> There are no such flags.  The -O options are *not* shorthand for
> collections of -f options; I know the documentation makes it sound
> that way.  -Os in particular has direct and complex effects on code
> generation.
> 
> zw


  Ah, I stand corrected.  Would it be accurate to say that they are _both_
shorthand for a set of -f options _and_ _also_ control a set of other
behaviours, which entail enabling, disabling, or fine-tuning the parameters
of other optimisations that do not correspond directly to -f options ?

    cheers, 
      DaveK
-- 
Can't think of a witty .sigline today....