RFR: 8281701: Mismatched array filling pattern can be stopped earlier

[Yi Yang]

This patch 1. checks the valid counted loop earlier 2. checks stored value/stored address earlier 3. During array filling matching, unpack_offsets is a reverse operation of array_element_address, so it seems that unpacked elements are always invariant: [0]:Constant [1]:ConvI2B/LShift/Phi(??I don't know why we could find a phi, but I kept the original code) 4. Some refactor.

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Commit messages:
 - 8281701 Mismatched array filling pattern can be stopped earlier

Changes: https://git.openjdk.java.net/jdk/pull/7454/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7454&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281701
  Stats: 285 lines in 3 files changed: 151 ins; 90 del; 44 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7454.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7454/head:pull/7454

PR: https://git.openjdk.java.net/jdk/pull/7454