> You can't use popc in the default implementations, most sparc64 > chips do not implement popc in hardware and it must be emulated. Mea culpa! I was reading the various architecture manuals (mostly about umulxhi support) and noticed that popc was in the oldest original SPARCv9 architecture manuals, so I assumed it had universal hardware support. Damn manuals not mentioning a Really Important Detail like that! (They *do* document the lack of hardware support for quad floating point, but no such warning appears in the 2011 or 2015 architecture manuals.) With your prompting, I found mention of this in a Java feature request: https://bugs.java.com/bugdatabase/view_bug.do?bug_id=6378821 And of course, T4 has lzcnt and doesn't care. Sorry for wasting your time. (And mine.) P.S. I do think *some* earlier processors have hardware popc support; e.g. the T3 manual documents the instruction latency, which implies hardware support. But dealing with a feature flag is not nearly so simple a patch. P.P.S. __NG4fls cn be simplified to ENTRY(__NG4fls) LZCNT_O0_G2 !lzcnt %o0, %g2 retl xor %g2, 63, %o0 ENDPROC(__NG4fls)
