RFR: 8173472: AArch64: C1 comparisons with null only use 32-bit instructions

[Roland Westrelin]

Hi David,

> Well that's what I'm questioning. Maybe one of the compiler folk 
> (Roland?) can chime in. C1 was 32-bit only but there was a proprietary 
> 64-bit version. I don't know if OpenJDK ever supported a 64-bit C1. The 
> code would have to have been adapted for tiered compilation.

Tiered runs 64-bit c1 so the code is well tested. Building a client only
64 bit VM is forbidden by the build scripts and is as far as I know
considered unsupported but given how much testing it gets with tiered
compilation, in practice, it's on par with 32 bit c1.

Roland.