This patch expands the use of a hash table for secondary superclasses to the interpreter, C1, and runtime. It also adds a C2 implementation of hashed lookup in cases where the superclass isn't known at compile time.
HotSpot shared runtime ---------------------- Building hashed secondary tables is now unconditional. It takes very little time, and now that the shared runtime always has the tables, it might as well take advantage of them. The shared code is easier to follow now, I think. There might be a performance issue with x86-64 in that we build HotSpot for a default x86-64 target that does not support popcount. This means that HotSpot C++ runtime on x86 always uses a software emulation for popcount, even though the vast majority of machines made for the past 20 years can do popcount in a single instruction. It wouldn't be terribly hard to do something about that. Having said that, the software popcount is really not bad. x86 --- x86 is rather tricky, because we still support `-XX:-UseSecondarySupersTable` and `-XX:+UseSecondarySupersCache`, as well as 32- and 64-bit ports. There's some further complication in that only `RCX` can be used as a shift count, so there's some register shuffling to do. All of this makes the logic in macroAssembler_x86.cpp rather gnarly, with multiple levels of conditionals at compile time and runtime. AArch64 ------- AArch64 is considerably more straightforward. We always have a popcount instruction and (thankfully) no 32-bit code to worry about. Generally --------- I would dearly love simply to rip out the "old" secondary supers cache support, but I've left it in just in case someone has a performance regression. The versions of `MacroAssembler::lookup_secondary_supers_table` that work with variable superclasses don't take a fixed set of temp registers, and neither do they call out to to a slow path subroutine. Instead, the slow patch is expanded inline. I don't think this is necessarily bad. Apart from the very rare cases where C2 can't determine the superclass to search for at compile time, this code is only used for generating stubs, and it seemed to me ridiculous to have stubs calling other stubs. I've followed the guidance from @iwanowww not to obsess too much about the performance of C1-compiled secondary supers lookups, and to prefer simplicity over absolute performance. Nonetheless, this is a complicated patch that touches many areas. ------------- Commit messages: - Cleanup tests - small - Small - Temp - Merge remote-tracking branch 'refs/remotes/origin/JDK-8331658-work' into JDK-8331658-work - Fix x86-32 - Fix x86 - Temp - Temp - Temp - ... and 16 more: https://git.openjdk.org/jdk/compare/747e1e47...7d7694cc Changes: https://git.openjdk.org/jdk/pull/19989/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19989&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8331341 Stats: 886 lines in 13 files changed: 755 ins; 69 del; 62 mod Patch: https://git.openjdk.org/jdk/pull/19989.diff Fetch: git fetch https://git.openjdk.org/jdk.git pull/19989/head:pull/19989 PR: https://git.openjdk.org/jdk/pull/19989
