[jdk13u-dev] RFR: 8254790: SIGSEGV in string_indexof_char and stringL_indexof_char intrinsics

[Sergey Nazarkin]

Hi! Please review the backport of JDK-8254790.  The patch fixes SIGSEGV and is required for code sync with jdk11,15. The patch is taken from jdk15 since the original one can't be applied cleanly due to reasons described https://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2020-October/040943.html

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Commit messages:
 - Backport afcf14912e9e37499444108e4b9c08d9bd6ef64f

Changes: https://git.openjdk.java.net/jdk13u-dev/pull/170/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=170&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254790
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk13u-dev/pull/170.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/170/head:pull/170

PR: https://git.openjdk.java.net/jdk13u-dev/pull/170