[aarch64-port-dev ] RFR: 8129426: aarch64: add support for PopCount in C2

[Andrew Haley]

On 06/22/2015 03:59 PM, Edward Nevill wrote:
> On Mon, 2015-06-22 at 15:04 +0100, Andrew Haley wrote:
>> On 06/22/2015 02:23 PM, Edward Nevill wrote:
>>> Aarch64 currently does not support the PopCountI and PopCountL nodes in aarch64.ad
>>
>>>
>>> Please review and if OK I will push,
>>
>> Shouldn't mov in the IregI case be movw?  And iRegI be iRegIorL2I?
> 
> No. It needs 0s in the top 32 bits.
> 
> The reason is that the following CNT instruction is only available in 8B or 16B forms.
> 
> It was iRegIorL2I before, I changed it to IregI because of this problem.

Well, you're asking for trouble.  We've tried to make sure that the
top half of an int register is always zero, but it's hard absolutely
to guarantee it in all cases.  Does movw to a vector register really
not clear the top 32 bits of the dest?

Andrew.