CR for RFR 8129376

Berg, Michael C michael.c.berg at
Tue Sep 20 23:02:58 UTC 2016

Hi Folks,

Performance on client x86 targets was hampered in two SPECjvm98 metrics (mpegaudio and  mtrt) for 32-bit since we added AVX512.  I also checked to make sure only client on x86-32 was affected.  I have mitigated this by altering the xmm pad modeling in the x86-32-bit machine description so that register allocation cannot see the dummy definitions, enabling the desired performance while retaining correctness for 32-bit on AVX512.

This code was tested as follows: hotspot jreg, SPECjvm2008, SPECjvm98 on hsw, skx and knl targets complete with no issues on 32-bit.  These changes do not alter behavior on x86-64.



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