CR for RFR 8129376
vladimir.kozlov at oracle.com
Tue Sep 20 23:15:52 UTC 2016
Changes look good.
Michael, can you explain how pads affected code generation to cause regression?
.ad changes affects Server VM (c2) code generation. Do you need it based on performance numbers? TRy running Server VM with -XX:-TieredCompilation.
On 9/20/16 4:02 PM, Berg, Michael C wrote:
> 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.
> Bug-id: https://bugs.openjdk.java.net/browse/JDK-8129376
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