regressions in arm64_altjit r2r jobs: temp != nullptr

[sandreenko]

Some tests are failing after dotnet/coreclr#18346, for example b393481 fails with Assertion failed 'temp != nullptr' in 'TestAnonymousTypes.Program:Main(ref):int' (IL size 534)\r\n\r\n File: d:\\j\\workspace\\x64_arm64_alt---840786b4\\src\\jit\\regset.cpp Line: 676.

[sandreenko]

cc @dotnet/jit-contrib

[CarolEidt]

I had taken a look at this before @sandreenko pointed me at this issue. @jashook - I see that it's assigned to you. I can look further if you'd like. It seems (from an initial look at a jitdump) that the register allocator is tracking int and long spill-temps separately, which it shouldn't be doing.

[jashook]

Feel free to poach the issue, I will not get to it for a little.