Daniel Lundén

Looks interesting @merykitty! I will also review this.

> The question is how do you reliably get 94 on the igvn queue. In this particular case, PhiNode::Ideal() creates 451 and enqueues it on the igvn queue with register_new_node_with_optimizer()....

Thanks for the comments @dean-long. There is no limit on register mask size, besides that it has to fit in memory. I allocate extended register mask memory in `comp_arena`, but...

> but I realize I should add an explicit check to see if the allocation succeeds or not when growing the register mask (and bail out if it doesn't) After...

@dean-long > Does C2 have a maximum frame size? I'll investigate, unless someone already has the answer. > Don't we still need RegMask::can_represent() checks to make sure regmask size doesn't...

Thanks to @robcasloz for the comments and contributions! /contributor add @robcasloz

> Would it be possible to 1) extend test/hotspot/gtest/opto/test_regmask.cpp with tests that exercise extended RegMasks and 2) re-run the standard test tiers with a (temporary) RM_SIZE value that is low...

After doing some simple performance testing, it looks like the best option may, after all, be to simply use bigger static register masks. Please hold off a bit with reviewing!...

I explored the possibility of calculating a static upper bound for register mask size given that parameters must fit in 255 32-bit words (from the JVM spec). My conclusion is...

> As we discussed on our previous meeting Aarch64 has very small registers mask - only 10 words. Can you look if that enough or we should increase static size...