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Date: Tue, 20 Oct 1998 10:35:59 -0500 (EST)
From: Steven Snyder <ssnyder AT indy DOT net>
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To: pgcc mailing list <beastium-list AT Desk DOT nl>
Subject: What does the -O9 switch do?
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Sender: Marc Lehmann <pcg AT goof DOT com>
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The pgcc Web page documents the optimizations enabled by -O3 through -O6,
but is silent on higher optimizations.  (The gcc man pages don't mention
anything higher than -O3.)  What, for instance, does -O9 do that -O6 does
not?

Since the egcs/pgcc 1.1a compilers no longer write the switches to the
generated asm file (can we please, please, please get that feature back?)
there's no way to tell which flags were used in a given compilation.

Binary files built with -O6 and -O9 do compare differently sometimes (for
instance, on the Linux kernel bzImage file).  Obviously the higher
optimization specified generated different code, but what?

Thanks.