# Reproduce
```
Run jdk/incubator/vector/Int256VectorTests.java on AVX512 machines
```

# Symptom
```
#
# A fatal error has been detected by the Java Runtime Environment:
#
# Internal Error (/home/jvm/jiefu/open/jdk/src/hotspot/cpu/x86/assembler_x86.cpp:8714), pid=83279, tid=83294
# assert(((dst_enc < 16 && nds_enc < 16 && src_enc < 16) || (!attributes->is_legacy_mode()))) failed: XMM register should be 0-15

# Problematic frame:
# V [libjvm.so+0x5c52b3] Assembler::vex_prefix_and_encode(int, int, int, Assembler::VexSimdPrefix, Assembler::VexOpcode, InstructionAttr*) [clone .constprop.98]+0x213
```