> Can I please get reviews for this PR? > > The most common and frequent use of NonEscaping Phis merging object > allocations is for debugging information. The two graphs below show numbers > for Renaissance and DaCapo benchmarks - similar results are obtained for all > other applications that I tested. > > With what frequency does each IR node type occurs as an allocation merge > user? I.e., if the same node type uses a Phi N times the counter is > incremented by N: > >  > > What are the most common users of allocation merges? I.e., if the same node > type uses a Phi N times the counter is incremented by 1: > >  > > This PR adds support scalar replacing allocations participating in merges > that are used as debug information OR as a base for field loads. I plan to > create subsequent PRs to enable scalar replacement of merges used by other > node types (CmpP is next on the list) subsequently. > > The approach I used for _rematerialization_ is pretty straightforward. It > consists basically in: 1) Extend SafePointScalarObjectNode to represent > multiple SR objects; 2) Add a new Class to support rematerialization of SR > objects part of merges; 3) Patch HotSpot to be able to serialize and > deserialize debug information related to allocation merges; 4) Patch C2 to > generate unique types for SR objects participating in some allocation merges. > > The approach I used for _enabling the scalar replacement of some of the > inputs of the allocation merge_ is also pretty straight forward: call > `MemNode::split_through_phi` to, well, split AddP->Load* through the merge > which will render the Phi useless. > > I tested this with JTREG tests tier 1-4 (Windows, Linux, and Mac) and didn't > see regression. I also tested with several applications and didn't see any > failure. I also ran tests with "-ea -esa -Xbatch -Xcomp > -XX:+UnlockExperimentalVMOptions -XX:-TieredCompilation -server > -XX:+IgnoreUnrecognizedVMOptions -XX:+UnlockDiagnosticVMOptions > -XX:+StressLCM -XX:+StressGCM -XX:+StressCCP" and didn't observe any related > failures.
Cesar Soares Lucas has updated the pull request incrementally with one additional commit since the last revision: Addressing PR review 2: refactor & reuse MacroExpand::scalar_replacement method. ------------- Changes: - all: https://git.openjdk.org/jdk/pull/12897/files - new: https://git.openjdk.org/jdk/pull/12897/files/5ef86371..3752b21a Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=12897&range=05 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12897&range=04-05 Stats: 346 lines in 3 files changed: 113 ins; 106 del; 127 mod Patch: https://git.openjdk.org/jdk/pull/12897.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/12897/head:pull/12897 PR: https://git.openjdk.org/jdk/pull/12897
