C2 will now remove the slow call to `ValueObjectMethods::isSubstitutable(Alt)` whenever it's able to determine the layout of one of the operands. It will then emit code to directly compare the fields.
This patch also contains an intrinsic for `_getFieldMap` that will be used by the new core-libs implementation of the substitutability check ([JDK-8370450](https://bugs.openjdk.org/browse/JDK-8370450)) that's used by the interpreter / C1 and as a slow path in C2. When browsing code, I marked a few rough edges in unrelated code for follow-up cleanups with the corresponding bug numbers. Testing: tier1-tier6 + valhalla-comp-stress Thanks, Tobias ------------- Commit messages: - More refactoring, better comments - More comments, removing workaround - Merge - v5 - Refactoring v4 - Refactoring v3 - Refactoring, more checks, new test - Merge branch 'lworld' into JDK-8228362 - All tests pass - Diagnostic printing - ... and 10 more: https://git.openjdk.org/valhalla/compare/9eead93b...4d711c87 Changes: https://git.openjdk.org/valhalla/pull/1823/files Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1823&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8228361 Stats: 1503 lines in 30 files changed: 1266 ins; 106 del; 131 mod Patch: https://git.openjdk.org/valhalla/pull/1823.diff Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1823/head:pull/1823 PR: https://git.openjdk.org/valhalla/pull/1823
