RFR: 8294816: C2: Math.min/max vectorization miscompilation

[Bhavana Kilambi]

C2 miscompiles during auto-vectorization of MinI/MaxI nodes when "short" type operands are involved. When a short and an integer value is compared, C2 generates vector min/max nodes for "short" types which does not result in correct output as it disregards the higher order bits of the integer input. Java API for Math.min/max also only supports the int, long, float and double types but not the subword integer types namely - char, byte and short. Hence, char/short/byte min/max vector instructions should not be generated.
This patch ensures that MaxV and MinV vector nodes are only generated for the "int" type for MaxI and MinI nodes during auto-vectorization.

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Commit messages:
 - 8294816: C2: Math.min/max vectorization miscompilation

Changes: https://git.openjdk.org/jdk/pull/10944/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10944&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8294816
  Stats: 139 lines in 4 files changed: 139 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/10944.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10944/head:pull/10944

PR: https://git.openjdk.org/jdk/pull/10944