[15] RFR(S): 8239009: C2: Don't use PSHUF to load scalars from memory on x86

[Vladimir Ivanov]

http://cr.openjdk.java.net/~vlivanov/8239009/webrev.00
https://bugs.openjdk.java.net/browse/JDK-8239009

Mem-to-reg variants of PSHUF instructions load 16 bytes from memory.

Switch to reg-to-reg variants and perform scalar loads of proper size 
instead.

Testing: hs-precheckin-comp,hs-tier1,hs-tier2

Thanks!

Best regards,
Vladimir Ivanov