[PATCH] Fold together repeated tests for divisibility by constants

[Richard Smith]

On Thu, Jul 31, 2014 at 4:58 PM, Joerg Sonnenberger <joerg at britannica.bec.de
> wrote:

> On Mon, Jul 21, 2014 at 06:55:05PM -0700, Richard Smith wrote:
> > Index: include/llvm/ADT/APInt.h
> > ===================================================================
> > --- include/llvm/ADT/APInt.h  (revision 213404)
> > +++ include/llvm/ADT/APInt.h  (working copy)
> > @@ -1756,13 +1756,13 @@
> >  /// \brief Returns the floor log base 2 of the specified APInt value.
> >  inline unsigned logBase2(const APInt &APIVal) { return
> APIVal.logBase2(); }
> >
> > -/// \brief Compute GCD of two APInt values.
> > +/// \brief Compute GCD of two unsigned APInt values.
> >  ///
> >  /// This function returns the greatest common divisor of the two APInt
> values
> >  /// using Euclid's algorithm.
> >  ///
> >  /// \returns the greatest common divisor of Val1 and Val2
> > -APInt GreatestCommonDivisor(const APInt &Val1, const APInt &Val2);
> > +APInt GreatestCommonDivisor(APInt Val1, APInt Val2);
>
> Doesn't this create an unnecessary copy in many common cases?


This is no worse than the previous algorithm, which began by making copies
of both of its arguments, and is better in the case where the arguments are
temporaries.
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