http://hg.openjdk.java.net/valhalla/valhalla/file/7c637fd25e7d/src/hotspot/cpu/x86/macroAssembler_x86.cpp#l6369

Most of the two functions MacroAssembler::shuffle_value_args() and MacroAssembler::unpack_value_args() have CPU-independent code. They should be refactored to make it easier to port to other CPU architectures.

See the following mail thread for discussion
https://mail.openjdk.java.net/pipermail/valhalla-dev/2019-June/006044.html