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Subject: Re: [boost] Proposal/InterestCheck: Boost.Geom
From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2009-01-27 12:44:15

Anis Benyelloul wrote:
> (such as if you
> are packing the X and Y coordinates in the same machine word,
> geom::point<>::operator==() will be able to compare both coordinates with the
> same operation, instead of the generic x1==x2 && y1==y2).

I have wondered about this particular optimisation before and your
mention made me investigate. gcc for ARM seems to make the
optimisation but surprisingly the x86 version doesn't. Test code:

struct pair {
   short a;
   short b;

int compare_pair(struct pair p1, struct pair p2)
   return p1.a==p2.a && p1.b==p2.b;

int compare_int(int i1, int i2)
   return i1==i2;

Is there anything in the language that makes this sort of thing
difficult for the compiler? I don't think so.


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