[aarch64-port-dev ] RFR: 8221658: aarch64: add necessary predicate for ubfx patterns

[Yangfei (Felix)]

Thanks for reviewing.  Yes, I will take a look at other similar issues. 

> 
> On 4/9/19 2:36 AM, Yangfei (Felix) wrote:
> >     This can pass the fuzz test and we got the same output as when the test is
> executed on the x86 platform.
> >     New webrev: http://cr.openjdk.java.net/~fyang/8221658/webrev.02/
> >     This also incorporates the following two constraints:
> >     2. mask != 0
> >     3. rshift + width <= 32/64  (width = exact_log2(mask+1))
> >
> >     JTreg tested with a fastdebug build, OK?
> 
> That looks right, thanks.
> 
> Because C2 does not mask immediate shifts, there are other lurking
> bugs.  It would be good to systematically mask all immediate shift
> counts throughout aarch64.ad in a separate patch.
> 
> Would you like to do that work? Thanks.
>