[NativeAOT-LLVM] Slightly more precise null checking

[SingleAccretion]

This change reduces the number of instances where we have to use the longer addr < 1024 null check form by being a bit more precise about which addresses we can consider "null or valid" aka "not an almost-null compiler-created byref".

Diffs (WasmDebugging):

Summary of Code Size diffs:
(Lower is better)

Total bytes of base: 674872
Total bytes of diff: 670850
Total bytes of delta: -4022 (-0.60% % of base)
Average relative delta: -4.19%
    diff is an improvement
    average relative diff is an improvement

Top method regressions (percentages):
          16 ( 2.03% of base) : 1278.dasm - S_P_CoreLib_System_Runtime_EH__DispatchEx
           7 ( 1.61% of base) : 1354.dasm - S_P_CoreLib_System_Number_BigInteger__Add
           6 ( 1.39% of base) : 1391.dasm - S_P_CoreLib_System_Environment__GetEnvironmentVariableCore
           2 ( 0.54% of base) : 1389.dasm - S_P_CoreLib_System_SpanHelpers__ClearWithReferences

Top method improvements (percentages):
        -404 (-30.98% of base) : 1090.dasm - S_P_TypeLoader_Internal_Runtime_TypeLoader_TypeLoaderEnvironment__TryGetNamedTypeForMetadata
        -279 (-25.36% of base) : 1073.dasm - S_P_Reflection_Execution_Internal_Reflection_Execution_ExecutionEnvironmentImplementation__GetTypeSequence
         -81 (-21.89% of base) : 1343.dasm - S_P_CoreLib_System_Runtime_EH_PreciseVirtualUnwindFrame__GetLast
         -44 (-18.18% of base) : 1312.dasm - S_P_CoreLib_System_Runtime_EH_EHTable__GetClauseInfo
         -34 (-15.96% of base) : 1296.dasm - S_P_StackTraceMetadata_Internal_StackTraceMetadata_StackTraceMetadata_PerModuleMethodNameResolver_StackTraceData____GetFieldHelper
         -34 (-15.96% of base) : 1293.dasm - S_P_CoreLib_System_Runtime_CompilerServices_ClassConstructorRunner_Cctor____GetFieldHelper
         -70 (-15.87% of base) : 1342.dasm - S_P_CoreLib_System_Runtime_PreciseVirtualUnwindInfo__Parse
         -34 (-15.81% of base) : 1160.dasm - S_P_CoreLib_System_Collections_Generic_Dictionary_2_Enumerator<System___Canon__System___Canon>____GetFieldHelper
         -27 (-15.70% of base) : 1094.dasm - S_P_CoreLib_System_Collections_Concurrent_ConcurrentUnifierW_2_Entry<S_P_CoreLib_System_Reflection_Runtime_TypeInfos_NativeFormat_NativeFormatRuntimeNamedTypeInfo_UnificationKey__System___Canon>____GetFieldHelper
         -27 (-15.70% of base) : 1294.dasm - S_P_CoreLib_System_Threading_SyncTable_Entry____GetFieldHelper
         -27 (-15.52% of base) : 1166.dasm - S_P_CoreLib_System_Collections_Concurrent_ConcurrentUnifier_2_Entry<Int32__System___Canon>____GetFieldHelper
         -27 (-15.34% of base) : 1017.dasm - S_P_CoreLib_System_Collections_Concurrent_ConcurrentUnifier_2_Entry<System___Canon__System___Canon>____GetFieldHelper
         -27 (-15.34% of base) : 1159.dasm - S_P_CoreLib_System_Collections_Generic_Dictionary_2_Entry<System___Canon__System___Canon>____GetFieldHelper
         -20 (-14.39% of base) : 1447.dasm - S_P_CoreLib_System_Collections_Generic_HashSet_1_Entry<Char>____GetFieldHelper
         -20 (-14.39% of base) : 1274.dasm - S_P_CoreLib_System_Reflection_Runtime_TypeInfos_NativeFormat_NativeFormatRuntimeNamedTypeInfo_UnificationKey____GetFieldHelper
         -20 (-14.39% of base) : 1165.dasm - S_P_CoreLib_System_Collections_Concurrent_ConcurrentUnifierWKeyed_2_Entry<S_P_CoreLib_System_Reflection_Runtime_TypeInfos_RuntimeHasElementTypeInfo_UnificationKey__System___Canon>____GetFieldHelper
         -20 (-14.39% of base) : 1477.dasm - S_P_CoreLib_System_Collections_Concurrent_ConcurrentUnifierWKeyed_2_Entry<S_P_CoreLib_System_Reflection_Runtime_TypeInfos_RuntimeConstructedGenericTypeInfo_UnificationKey__System___Canon>____GetFieldHelper
         -20 (-14.39% of base) : 1072.dasm - S_P_CoreLib_System_Collections_Concurrent_ConcurrentUnifierWKeyed_2_Entry<S_P_CoreLib_System_Reflection_Runtime_TypeInfos_RuntimeFunctionPointerTypeInfo_UnificationKey__System___Canon>____GetFieldHelper
         -20 (-14.39% of base) : 1164.dasm - S_P_CoreLib_System_Runtime_CompilerServices_ConditionalWeakTable_2_Entry<System___Canon__System___Canon>____GetFieldHelper
         -13 (-12.75% of base) : 1292.dasm - S_P_CoreLib_System_Runtime_CompilerServices_ClassConstructorRunner_BlockingRecord____GetFieldHelper

483 total methods with Code Size differences (479 improved, 4 regressed)

[yowl]

The eventpipe failure is annoying, especially as the actual error doesn't seem to be logged.

[SingleAccretion]

The eventpipe failure is annoying, especially as the actual error doesn't seem to be logged.

Suspect it's the same as dotnet/runtime#117513 (comment). Let's rerun...

[yowl]

Thanks, nice.