Arm64: RCPC, DC ZVA and probably RDM ISAs are never detected on win-arm64

[EgorBo]

It turns out the following features are never detected for Windows-arm64 (thanks to @mcfi who found it out):

• RCPC (e.g. Windows-arm64 does not benefit from https://github.com/dotnet/runtime/pull/67384)
• DC ZVA (used for zeroing of large data by JIT)
• RDM (used in System.Runtime.Intrinsics.Arm.Rdm)

Mostly because Windows API IsProcessorFeaturePresent doesn't provide flags for https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-isprocessorfeaturepresent for those

category:correctness theme:intrinsics skill-level:beginner cost:small impact:small

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Issue Details

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It turns out the following features are never detected for Windows-arm64 (thanks to @mcfi who found it out): - RCPC (e.g. Windows-arm64 does not benefit from https://github.com/dotnet/runtime/pull/67384) - DC ZVA (used for zeroing of large data by JIT) - RDM (used in System.Runtime.Intrinsics.Arm.Rdm) Mostly because Windows API `IsProcessorFeaturePresent ` doesn't provide flags for https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-isprocessorfeaturepresent for those

Author:	EgorBo
Assignees:	-
Labels:	`area-CodeGen-coreclr`
Milestone:	8.0.0

[EgorBo]

Marking as 8.0.0 but if we find a quick way to detect those + detect improvements we, probably, can try to backport it to 7.0.0 (all of those should be presented on Amperes)

[tannergooding]

Worth noting that the docs are out of date somewhat. The full list of flags as of 10.0.22621.0 SDK is the below. This doesn't include the flags being asked about, but its good to double check the um/winnt.h header anyways:

#define PF_FLOATING_POINT_PRECISION_ERRATA           0   
#define PF_FLOATING_POINT_EMULATED                   1   
#define PF_COMPARE_EXCHANGE_DOUBLE                   2   
#define PF_MMX_INSTRUCTIONS_AVAILABLE                3   
#define PF_PPC_MOVEMEM_64BIT_OK                      4   
#define PF_ALPHA_BYTE_INSTRUCTIONS                   5   
#define PF_XMMI_INSTRUCTIONS_AVAILABLE               6   
#define PF_3DNOW_INSTRUCTIONS_AVAILABLE              7   
#define PF_RDTSC_INSTRUCTION_AVAILABLE               8   
#define PF_PAE_ENABLED                               9   
#define PF_XMMI64_INSTRUCTIONS_AVAILABLE            10   
#define PF_SSE_DAZ_MODE_AVAILABLE                   11   
#define PF_NX_ENABLED                               12   
#define PF_SSE3_INSTRUCTIONS_AVAILABLE              13   
#define PF_COMPARE_EXCHANGE128                      14   
#define PF_COMPARE64_EXCHANGE128                    15   
#define PF_CHANNELS_ENABLED                         16   
#define PF_XSAVE_ENABLED                            17   
#define PF_ARM_VFP_32_REGISTERS_AVAILABLE           18   
#define PF_ARM_NEON_INSTRUCTIONS_AVAILABLE          19   
#define PF_SECOND_LEVEL_ADDRESS_TRANSLATION         20   
#define PF_VIRT_FIRMWARE_ENABLED                    21   
#define PF_RDWRFSGSBASE_AVAILABLE                   22   
#define PF_FASTFAIL_AVAILABLE                       23   
#define PF_ARM_DIVIDE_INSTRUCTION_AVAILABLE         24   
#define PF_ARM_64BIT_LOADSTORE_ATOMIC               25   
#define PF_ARM_EXTERNAL_CACHE_AVAILABLE             26   
#define PF_ARM_FMAC_INSTRUCTIONS_AVAILABLE          27   
#define PF_RDRAND_INSTRUCTION_AVAILABLE             28   
#define PF_ARM_V8_INSTRUCTIONS_AVAILABLE            29   
#define PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE     30   
#define PF_ARM_V8_CRC32_INSTRUCTIONS_AVAILABLE      31   
#define PF_RDTSCP_INSTRUCTION_AVAILABLE             32   
#define PF_RDPID_INSTRUCTION_AVAILABLE              33   
#define PF_ARM_V81_ATOMIC_INSTRUCTIONS_AVAILABLE    34   
#define PF_MONITORX_INSTRUCTION_AVAILABLE           35   
#define PF_SSSE3_INSTRUCTIONS_AVAILABLE             36   
#define PF_SSE4_1_INSTRUCTIONS_AVAILABLE            37   
#define PF_SSE4_2_INSTRUCTIONS_AVAILABLE            38   
#define PF_AVX_INSTRUCTIONS_AVAILABLE               39   
#define PF_AVX2_INSTRUCTIONS_AVAILABLE              40   
#define PF_AVX512F_INSTRUCTIONS_AVAILABLE           41   
#define PF_ERMS_AVAILABLE                           42   
#define PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE        43   
#define PF_ARM_V83_JSCVT_INSTRUCTIONS_AVAILABLE     44   

[EgorBo]

Closed via https://github.com/dotnet/runtime/pull/82527