Base64 appears to give different (wrong) results in some rare cases when AVX3 is enabled. This has been observed in one of our services.

The attached reproducer fails reliably with -XX:UseAVX3 on my host with these CPU details (an AWS EC2 c6i.large instance):

```
vendor_id : GenuineIntel
cpu family : 6
model : 106
model name : Intel(R) Xeon(R) Platinum 8375C CPU @ 2.90GHz
stepping : 6
```

The same reproducer passes reliably with `-XX:UseAVX=2`.

```
java -XX:UseAVX=2 Base64Avx3.java
Test complete, no invalid decodes detected

java -XX:UseAVX=3 Base64Avx3.java
Exception in thread "main" java.lang.IllegalStateException: Mismatch for iouMjY6PkJGSk5SVlpeYmZqbnJ2en6ChoqOkpaanqKmqq6ytrq+wsbKztLW2t7i5uru8vb6/wMHCw8TFxsfIycrLzM3Oz9DR0tPU1dbX2Nna29zd3t/g4eLj5OXm5+jp6uvs7e7v8PHy8/T19vf4+fr7/P3+/wABAgMEBQYHCAkKCwwNDg8QERITFBU=

Expected:
8A 8B 8C 8D 8E 8F 90 91 92 93 94 95 96 97 98 99 9A 9B 9C 9D 9E 9F A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 BA BB BC BD BE BF C0 C1 C2 C3 C4 C5 C6 C7 C8 C9 CA CB CC CD CE CF D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 DA DB DC DD DE DF E0 E1 E2 E3 E4 E5 E6 E7 E8 E9 EA EB EC ED EE EF F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 FA FB FC FD FE FF 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15

Actual:
8A 8B 8C 8D 8E 8F 90 91 92 93 94 95 96 97 98 99 9A 9B 9C 9D 9E 9F A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 BA BB BC BD BE BF C0 C1 C2 C3 C4 C5 C6 C7 C8 C9 CA CB CC CD CE CF D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 DA DB DC DD DE DF E0 E1 E2 E3 E4 E5 E6 E7 E8 E9 EA EB EC ED EE EF F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 FA FB FC FD FE FF 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14
at Base64Avx3.decodeAndCheck(Base64Avx3.java:68)
at Base64Avx3.main(Base64Avx3.java:55)
```

It may be related to JDK-8268276.

Note also that the bug requires that the CPU supports avx512bw *and* avx512vbmi.