[PATCH i386 5/8] [AVX-512] Extend vectorizer hooks.

Eric Botcazou ebotcazou@adacore.com
Thu Jan 2 15:12:00 GMT 2014

> Frankly speaking, I do not understand, what's wrong here.
> IMHO, this change is pretty mechanical: we just extend maximal aligment
> available. Because of 512-bit data types we now extend maximal aligment to
> 512 bits.

Nothing wrong per se, but...

> I suspect that an issue is here:
>   if (opt
>       && AGGREGATE_TYPE_P (type)
>       && TYPE_SIZE (type)
>       && TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST
>       && (TREE_INT_CST_LOW (TYPE_SIZE (type)) >= (unsigned) max_align
>           || TREE_INT_CST_HIGH (TYPE_SIZE (type)))
>       && align < max_align)
>     align = max_align;

...yes, bumping max_align has the unexpected side effect of changing the 
behavior for sizes between the old value and the new value because of this 
code.  I'm no x86 specialist, but I think that this should be fixed.

> Maybe we can split it and handle 256-bit aggregates separately?

Probably, and we should also add a warning just before the declaration of 
max_align, as well as investigate whether this didn't already happen when 
max_align was bumped from 128 to 256.

Eric Botcazou

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