RFR: 8365071: ARM32: JFR intrinsic jvm_commit triggers C2 regalloc assert

[Boris Ulasevich]

On 32-bit ARM, the jvm_commit JFR intrinsic builder feeds null (RegP) into a TypeLong Phi, causing mixed long/pointer register sizing and triggering the C2 register allocator assert(_num_regs == reg || !_num_regs).

The fix is trivial: use an appropriate ConL constant instead. This has no effect on 64-bit systems (the generated assembly is identical) but resolves a JFR issue on 32-bit systems.

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Commit messages:
 - 8365071: ARM32: JFR intrinsic jvm_commit triggers C2 regalloc assert

Changes: https://git.openjdk.org/jdk/pull/26684/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26684&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365071
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/26684.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26684/head:pull/26684

PR: https://git.openjdk.org/jdk/pull/26684