On 2014/02/11 13:24:43, jbramley wrote:
On 2014/02/11 13:05:16, jochen wrote:
> On 2014/02/11 13:02:04, Rodolph Perfetta wrote:
> > not lgtm.
> >
> > As Jacob explained the top bits shouldn't be read, if you found a case
where
> it
> > is, then there is another bug lurking and you are just hiding it.
>
> As mentioned above, LCodeGen::DoBoundsCheck compares x registers with
each
> other.
>
> So a better fix was to use ToRegister32 in DoBoundsCheck?
For the Integer32 representation, yes, though smi representations need a
64-bit
comparison, so you have to use the representation to select between
ToRegister
and ToRegister32. The constant-index case already does this, though it
gets it
wrong because it still compares an X-sized 'length' with the constant.
MulConstIS is an example of how this is handled elsewhere. We sometimes
also
split instructions for different representations (like DoAddI and DoAddS).
I guess I'm just unlucky, but the code following the bounds check can't cope
with the clobbered upper 32bit either... filed
https://code.google.com/p/v8/issues/detail?id=3149 to track this.
https://codereview.chromium.org/131333011/
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