On Tue, Jun 9, 2009 at 11:26 AM, Kaveh R. Ghazi<gh...@caip.rutgers.edu> wrote: > From: "Joseph S. Myers" <jos...@codesourcery.com> > >> On Mon, 8 Jun 2009, Kaveh R. Ghazi wrote: >> >>> Perhaps the only safe way to create the value, even in the presence of >>> rounding mode changes, is to use conj(3.I) ? >> >> Setting the __real__ and __imag__ parts of a temporary variable should >> always be reliable for making a complex number out of arbitrary real and >> imaginary parts. > > Well yes, but I meant for compile-time expressions that are exposed to fold > even at -O0. (Recall that I'm writing testcases for the MPC stuff.) I'm > not 100% confident that the temporary variable will always fold and it's too > verbose when repeatedly used in a testcase. With conj, the builtin will > always fold 3.I and won't do anything unexpected with rounding modes.
It should always be folded via CCP / value-numbering. If not that is a bug that needs to be fixed. Richard. > I was just wondering why -3.I was evaluating differently than 0-3.I and > whether it was a bug. Your explanation was very useful. > Thanks, > --Kaveh > >
