[aarch64-port-dev ] aarch64: Fix a bug in TestOptionsWithRanges of hotspot

[Yang Zhang]

In file src/cpu/aarch64/vm/stubGenerator_aarch64.cpp:2350,
BlockZeroingLowLimit is used as follows:
__ cmp(cnt_words, BlockZeroingLowLimit >> 3);

On aarch64 platform, the immediate in cmp instruction has 12
significant bits which could be 0xXXX or 0xXXX000. The immediate is
calculated by BlockZeroingLowLimit >> 3. So BlockZeroingLowLimit has
15 significant bits. It's low limit, and a vary large value isn't
meaningful. So the range of BlockZeroingLowLimit should be [1, 2^15 -
1].

On 28 June 2016 at 16:16, Andrew Haley <aph at redhat.com> wrote:
> On 28/06/16 05:09, Yang Zhang wrote:
>> Could someone please help to review and process attached patch for fixing
>> an issue about BlockZeroingLowLimit in hotspot openjdk9 aarch64?
>>
>> This issue is exposed by a test failure in hotspot jtreg openjdk9 for
>> aarch64
>>
>> runtime/CommandLine/OptionsValidation/TestOptionsWithRanges.java
>>
>> It is caused by improper range of BlockZeroingLowLimit.
>
> Surely this is just papering over the real bug.
>
> Andrew.
>