runtime-jit-experimental fails in JIT/opt/InstructionCombining/CompareZero

[jakobbotsch]

Example pipeline run: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1215527&view=results
Example console log: https://helixr18s23ayyeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-heads-main-dfaeef053c694d96ad/JIT.opt/1/console.5cd0ad9e.log

__tmp16_CompareZero.cs:253:11: error: ARM64: expected string not found in input
 //ARM64: {{^ *}} tbz {{x[0-9]+}}, #63, G_M{{[0-9]+}}_IG{{[0-9]+}}{{$}}

Test introduced by #120667. cc @jonathandavies-arm

Also cc @dotnet/jit-contrib

[dotnet-policy-service]

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
See info in area-owners.md if you want to be subscribed.

[a74nh]

Looks like this requires export DOTNET_JitStressProcedureSplitting=1 to reproduce.

The flag jump conditions to invert, and add extra branches.

Eg:
tbz x0, #63, G_M55703_IG04
->

tbnz    x0, #0, pc+1 instructions
b       (LARGEJMP)G_M55703_IG04
b       G_M55703_IG03

Other tests have similar issues (eg bgt -> ble).

I suggest adding DOTNET_JitStressProcedureSplitting=0 to the csproj