> Can I please get reviews for this PR to add support for the rematerialization > of scalar-replaced objects that participate in allocation merges? > > 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 *only* as debug information in SafePointNode and its > subclasses. Although there is a performance benefit in doing scalar > replacement in this scenario only, the goal of this PR is mainly to add > infrastructure to support the rematerialization of SR objects participating > in merges. I plan to create subsequent PRs to enable scalar replacement of > merges used by other node types (CmpP, Load+AddP, primarily) subsequently. > > The approach I used 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 allocation merges used only as debug information. > > I tested this with JTREG tests tier 1-4 (Windows, Linux, and Mac) and didn't > see regression that might be related. I also tested with several applications > and didn't see any failure.
Cesar Soares Lucas has updated the pull request incrementally with one additional commit since the last revision: Fix some typos and do some small refactorings. ------------- Changes: - all: https://git.openjdk.org/jdk/pull/12897/files - new: https://git.openjdk.org/jdk/pull/12897/files/ea67a304..3b492d2e Webrevs: - full: https://webrevs.openjdk.org/?repo=jdk&pr=12897&range=02 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12897&range=01-02 Stats: 72 lines in 8 files changed: 1 ins; 7 del; 64 mod Patch: https://git.openjdk.org/jdk/pull/12897.diff Fetch: git fetch https://git.openjdk.org/jdk pull/12897/head:pull/12897 PR: https://git.openjdk.org/jdk/pull/12897
