Path: utzoo!utgpu!attcan!uunet!super!udel!gatech!bloom-beacon!tut.cis.ohio-state.edu!accelerator.eng.ohio-state.edu!kaa.eng.ohio-state.edu!rob From: rob@kaa.eng.ohio-state.edu (Rob Carriere) Newsgroups: comp.lang.c Subject: Re: Rearranging FP expressions Message-ID: <662@accelerator.eng.ohio-state.edu> Date: 27 Sep 88 14:30:03 GMT References: <4700017@m.cs.uiuc.edu> Sender: uucp@super.ORG Reply-To: rob@kaa.eng.ohio-state.edu (Rob Carriere) Organization: Ohio State Univ, College of Engineering Lines: 21 In article <4700017@m.cs.uiuc.edu> wsmith@m.cs.uiuc.edu writes: >[...] >The problem: How can C know when it is safe to rearrange expressions, > especially floating point expressions. > >A proposed solution: > Expressions enclosed in double parentheses may not be rearranged, > all other expressions may be rearranged in "semantically valid" > ways. >[examples] This could lead to trouble with macro expansions. Otherwise it looks fine to me at least. Another way of doing this might be a pair of pragma's, one to say ``hands off this one'', and one to say ``you can totally optimize this''. I know it is dubious whether the current standard allows such pragmae (sp :-), but the original poster was talking about future efforts anyway. Rob Carriere