RFR: 8272873: Inlining should not depend on absolute call site counts

[Igor Veresov]

C2 considers absolute call site counts in its inlining decisions, which seems very wrong considering the asynchronous nature of profiling and background compilation (See InlineTree::should_inline()). It causes substantial over-inlining, which in presence of a depth-first inlining can lead to an early cut off. It also is inherently unstable. C2 already uses call frequency as an additional factor and it's better to consider only that in the inlining heuristic. I did extensive benchmarking it yielded almost no losses and single-digit wins (up to 5%) on some benchmarks. I think it's safe to remove/deprecate InlineFrequencyCount and continue using InlineFrequencyRatio instead. I found that converting the frequency computation to FP and setting InlineFrequencyRatio=0.25 (inline a method that is called a least 25% of the time) works best.

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Commit messages:
 - Inlining should not depend on absolute call site counts

Changes: https://git.openjdk.java.net/jdk/pull/5238/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5238&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272873
  Stats: 18 lines in 10 files changed: 1 ins; 13 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5238.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5238/head:pull/5238

PR: https://git.openjdk.java.net/jdk/pull/5238