[vectorIntrinsics] RFR: 8284459: Add x86 back-end implementation for LEADING and TRAILING ZEROS COUNT operations [v2]

[Sandhya Viswanathan]

On Fri, 15 Apr 2022 01:26:44 GMT, Sandhya Viswanathan <sviswanathan at openjdk.org> wrote:

>> Jatin Bhateja has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:
>> 
>>  - 8284459: Adding an exponent based leading zero count algorithm for integer vectors, its showing around 10-15% gain.
>>  - Merge branch 'vectorIntrinsics' of http://github.com/openjdk/panama-vector into JDK-8284459
>>  - 8284459: Add x86 back-end implementation for LEADING_ZERO_COUNT operation
>
> src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 4798:
> 
>> 4796:    vector_count_leading_zeros_byte_avx(dst, src, xtmp1, xtmp2, xtmp3, rtmp, vec_enc);
>> 4797:    // Add zero counts of lower byte and upper byte of a word if
>> 4798:    // upper byte holds a zero value.
> 
> Need to specify here that xmm1 is set to all zeros by vector_count_leading_zeros_byte_avx.

This is still pending.

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PR: https://git.openjdk.java.net/panama-vector/pull/189