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Re: g++ 4.3, troubles with C++ indexing idioms


On 7/24/07, Richard Guenther <richard.guenther@gmail.com> wrote:
For performance small arrays should be the same as individual members
(I can see the annoying fact that initialization is a headache - this has
annoyed me as well).  For larger arrays (>4 members), aliasing will
make a difference possibly, making the array variant slower.  Any union
variant is expected to be slower for aliasing reasons (we do not do
field-sensitive aliasing for unions).
Confirmed :)
And thanks for the clue about the threshold.

In the end I would still recommend to go with array variants.
I guess wishful thinking, or heresy, got me asking for a sanctioned
address-this-as-an-array idiom.; now i'll go with the flow and use
those 2nd class citizens of C++ aka array, even if i'm a bit sceptical
about the performance equivalence (granted it isn't as obvious as it
used to be, i need to investigate some more).
But for sure it can't be as terrible as unions...


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