[11] RFR(XS) 8209735: Disable avx512 by default

[Vladimir Kozlov]

https://bugs.openjdk.java.net/browse/JDK-8209735

I found several issues with avx512 code. Some are listed in bug report.
At this later time I suggest to switch off avx512 in JDK 11:

diff -r 7339b9e38182 src/hotspot/cpu/x86/globals_x86.hpp
--- a/src/hotspot/cpu/x86/globals_x86.hpp
+++ b/src/hotspot/cpu/x86/globals_x86.hpp
@@ -119,7 +119,7 @@
    product(bool, UseStoreImmI16, true,                                       \
            "Use store immediate 16-bits value instruction on x86")           \
                                                                              \
-  product(intx, UseAVX, 3,                                                  \
+  product(intx, UseAVX, 2,                                                  \
            "Highest supported AVX instructions set on x86/x64")              \
            range(0, 99)                                                      \

Tested tier1,hs-tier2.

-- 
Thanks,
Vladimir