RFR(M): 8213134: AArch64: vector shift failed with MaxVectorSize=8

[Vladimir Kozlov]

You are right. I think I was confused that you are not limiting MaxVectorSize but simple use min(16, MaxVectorSize).

The assert is fine.

Thanks,
Vladimir

On 11/20/18 10:28 PM, Yang Zhang (Arm Technology China) wrote:
> 
>> I don't see any checking or setting for MaxVectorSize in vm_version_aarch64.cpp.
>> In such case you will definitely hit your new assert Matcher::vector_shift_count_ideal_reg().
>> aarch64.ad code Matcher::vector_width_in_bytes() has limit vector size to 16 bytes. So using  MaxVectorSize > 16 will hit the assert.
> 
> Matcher::vector_width_in_bytes() limits vector size to min(16, MaxVectorSize).
> Matcher::vector_shift_count_ideal_reg() assert(MaxVectorSize >= size, "Length isn't supported");
> When MaxVectorSize is 8, size is 8.
> When MaxVectorSize is greater than or equal 16, size is 16.
> So (MaxVectorSize >= size) is always true.
> 
> Test cases of cr6340864 are passed with or without this new  assert.
> 
> Do I need to remove this new assert?
> 
> Regards
> Yang
> 
> 
> On 11/18/18 11:53 PM, Yang Zhang (Arm Technology China) wrote:
>> Hi,
>>
>> When I implemented AArch64 NEON for Vector API (http://openjdk.java.net/jeps/338), I found an issue about vector shift. I have a patch which could fix this issue. Could anyone help to review this patch?
>>
>> Webrev: http://cr.openjdk.java.net/~yzhang/8213134/webrev.01/
>> JBS:  https://bugs.openjdk.java.net/browse/JDK-8213134
>>
>> This patch is verified both in jdk/jdk master and panama/vectorIntrinsics, and tests are passed.
>> Hotspt jtreg contains the following test cases that can cover all the patterns of vector shift.  But only default option "-XX:MaxVectorSize=64" is tested, so this issue isn't detected. Now I add "-XX:MaxVectorSize=8", "-XX:MaxVectorSize=16" and "-XX:MaxVectorSize=32" to these jtreg tests in this patch.
>> compiler/c2/cr6340864/TestByteVect.java
>> compiler/c2/cr6340864/TestIntVect.java
>> compiler/c2/cr6340864/TestShortVect.java
>> compiler/codegen/TestCharVect2.java
>>
>> Regards
>> Yang
>>
>>
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