RFR (M) 8207746:C2: Lucene crashes on AVX512 instruction

[Viswanathan, Sandhya]

Recently there have been couple of high priority issues with regards to high bank of XMM register (XMM16-XMM31) usage by C2:
https://bugs.openjdk.java.net/browse/JDK-8207746
https://bugs.openjdk.java.net/browse/JDK-8209735

Please find below a patch which attempts to clean up the XMM register handling by using register groups.
http://cr.openjdk.java.net/~vdeshpande/xmm_reg/webrev.00/

The patch provides a restricted set of registers to the match rules in the ad file based on the underlying architecture.
The aim is to remove special handling/workaround from macro assembler and assembler.
By removing the special handling, the patch reduces the overall code size by about 1800 lines of code.

Your review and feedback is very welcome.

Best Regards,
Sandhya




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