[JDK-8275645](https://bugs.openjdk.java.net/browse/JDK-8275645), resulted in the loose of single-copy atomicity for reads in c2v_readFieldValue. This PR fixes that by using the `<type>_field_acquire` accessors for all aligned reads in c2v_readFieldValue and only using the `<type>_field` accessors for unaligned reads.
------------- Commit messages: - use <type>_field_acquire for aligned reads in c2v_readFieldValue Changes: https://git.openjdk.java.net/jdk/pull/6109/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6109&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8275874 Stats: 30 lines in 1 file changed: 2 ins; 18 del; 10 mod Patch: https://git.openjdk.java.net/jdk/pull/6109.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/6109/head:pull/6109 PR: https://git.openjdk.java.net/jdk/pull/6109
