RFR: 8334629: [BACKOUT] PhaseIdealLoop::conditional_move is too conservative [v3]

[Quan Anh Mai]

> Hi,
> 
> I cannot explain the regression, comparing the current mainline to JDK-21 reveals a decrease in performance, yet it is only for some combinations of OS-GC and perfasm shows that the hot regions (>99% of execution time) do not contain differences that can explain the results.
> 
> Consequently, with the advice of @TobiHartmann , I propose to effectively revert JDK-8319451 for the generation of `CMove`s inside loops. For those outside, the before-JDK-8319451 probability threshold is 0.001 and the current value is 0.01. I think the current value is more reasonable as evidenced by the benchmark added in JDK-8319451.
> 
> Please kindly review, thank you very much.
> Quan Anh

Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:

  ProblemList

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Changes:
  - all: https://git.openjdk.org/jdk/pull/19650/files
  - new: https://git.openjdk.org/jdk/pull/19650/files/caaee62b..b8819793

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19650&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19650&range=01-02

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/19650.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19650/head:pull/19650

PR: https://git.openjdk.org/jdk/pull/19650