[Bug target/17622] Non-optimal code sequence for floating point "x=0; x+=a*b;"

[bangerth at ices dot utexas dot edu]

------- Additional Comments From bangerth at ices dot utexas dot edu  2004-09-23 02:34 -------
Subject: Re:  Non-optimal code sequence for floating point
 "x=0; x+=a*b;"


>           /* Maybe simplify x + 0 to x.  The two expressions are equivalent
>              when x is NaN, infinite, or finite and nonzero.  They aren't
>              when x is -0 and the rounding mode is not towards -infinity,
>              since (-0) + 0 is then 0.  */

Another reason for me to use -ffast-math. Programs that rely on such 
semantics are just doing something intensely insane.

W.

-------------------------------------------------------------------------
Wolfgang Bangerth              email:            bangerth@ices.utexas.edu
                               www: http://www.ices.utexas.edu/~bangerth/




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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=17622