On Wed, 18 Sep 2024 12:54:34 GMT, Roman Kennke <rken...@openjdk.org> wrote:
>> src/hotspot/share/oops/markWord.inline.hpp line 90: >> >>> 88: ShouldNotReachHere(); >>> 89: return markWord(); >>> 90: #endif >> >> Is the ifdef _LP64 necessary, since UseCompactObjectHeaders should always be >> false for 32 bits? > > Kindof. The problem is that klass_shift is larger than 31, and shifting with > it would thus be UB and generate a compiler warning. I opted to simply not > compile any of that code in 32bit builds. We could also define klass_shift > differently on 32bit. > Long-term (maybe with Lilliput2/4-byte-headers?) it would be nice to > consolidate the header layout between 32 and 64 bit builds and not make any > distinction anywhere. E.g. define markWord (or objectHeader?) in a single > way, and use that to extract all the relevant stuff. It's not totally > unlikely that we deprecate 32-bit builds before that can happen, though. Ok. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1769069007
