RFR: 8256387: Unexpected result if patching an entire instruction on AArch64 [v2]

[Eric Liu]

> This patch fixed some potential risks in assembler_aarch64.hpp.
> 
> According to the C standard, shift operation is undefined if the shift
> count greater than or equals to the length in bits of the promoted left
> operand.
> 
> In assembler_aarch64.hpp, there are some utility functions for easily
> operating the encoded instructions. E.g.
> 
>         Instruction_aarch64::patch(address, int, int, uint64_t)
> 
> All those functions use `(1U << nbits) - 1` to calculate mask which may
> have some potential risks if `nbits` equals 32. That would be an
> unexpected result if someone intends to deal with an entire instruction.
> 
> To fix this issue, this patch simply uses `1ULL` to replace `1U`.

Eric Liu has updated the pull request incrementally with one additional commit since the last revision:

  uses pre-defined macro `right_n_bits` to get the right-most bits set.
  
  Change-Id: I456bcc883434b04527db912adaccc6a5f2dd96a0

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/1248/files
  - new: https://git.openjdk.java.net/jdk/pull/1248/files/08ce2fba..29ed5d66

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=1248&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=1248&range=00-01

  Stats: 6 lines in 1 file changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1248.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1248/head:pull/1248

PR: https://git.openjdk.java.net/jdk/pull/1248