RFR: 8327693: C1: LIRGenerator::_instruction_for_operand is only read by assertion code

[Denghui Dong]

Hi,

Please help review this change that moves _instruction_for_operand into ASSERT block since it is only read by assertion code in c1_LinearScan.cpp.

Thanks

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Commit messages:
 - 8327693: C1: LIRGenerator::_instruction_for_operand is only read by assertion code

Changes: https://git.openjdk.org/jdk/pull/18170/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18170&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327693
  Stats: 25 lines in 2 files changed: 12 ins; 9 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/18170.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18170/head:pull/18170

PR: https://git.openjdk.org/jdk/pull/18170