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From: Eljay Love-Jensen <eljay@adobe.com>
To: CSights <csights@fastmail.fm>, GCC-help <gcc-help@gcc.gnu.org>
Subject: Re: binary compiled with -O1 and w/ individual optimization flags are  not the same
Date: Fri, 29 Feb 2008 17:40:00 -0000	[thread overview]
Message-ID: <C3ED9C9B.1FAF%eljay@adobe.com> (raw)
In-Reply-To: <200802291215.47293.csights@fastmail.fm>

Hi CSights,

> Is there a way to have g++ tell me which flags it is actually using when
> compiling a program.  E.g. expand -O1 to the individual optimization flags at
> run time?

Yes.

I use this trick:

g++ -O1 -S -fverbose-asm -x c++ <(echo '') -o O1.s

cat O1.s

> Anyone have any other suggestions?

Keep in mind that -O1 or higher turns on many more "behind the scenes"
optimizations than just those that are twiddle-able with the -f optimization
flags.

And keep in mind that -O0 disables all optimizations, irregardless of
specified -f optimization flags (which are ignored).

HTH,
--Eljay

  parent reply	other threads:[~2008-02-29 17:28 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-29 17:28 CSights
2008-02-29 17:28 ` Andrew Haley
2008-02-29 17:40 ` Eljay Love-Jensen [this message]
2008-02-29 20:15 ` Brian Dessent
2008-02-29 22:38   ` CSights
     [not found]     ` <47C88B66.A501ABD6@dessent.net>
2008-03-01 15:59       ` CSights
2008-03-01 17:26         ` Tim Prince
2008-03-01 18:22         ` Brian Dessent
2008-03-05 18:13           ` CSights

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