RFR: 8252505: C1/C2 compiler support for blackholes

[Andrew Dinn]

On Tue, 24 Nov 2020 19:34:06 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> But more importantly, I'd like to see if doing this in .ad is even acceptable. That's my major question here.

The problem being that this introduces extra call handling logic into the ad file which clouds the implementation of the arch-specific handling of a `CallJavaNode` 

Modulo the supports_blackholes switch that logic is essentially the same on all platforms, isn't it? Why can you not just fold the relevant case handling into the generated matcher code? Wouldn't that just require a special case switch to decide whether to use the AD file rule to reduce a `CallJavaNode` vs reducing it to nothing?

-------------

PR: https://git.openjdk.java.net/jdk/pull/1203