Improve Arm64 for .NET12 #135627

We will continue to improve the Arm64 port for .NET12. It will include improving support for SVE, Vector-Length-Agnostic, PAC-RET along with overall code quality and performance improvements.

Vector- Length-Agnostic SVE

• Complete support for JIT
  Arm64-SVE: Support accessing unknown-sized Tier-0 locals from Tier-1 (OSR) #132752
  Arm64-SVE: Add scheme for scalable SVE state in the CONTEXT record #133152
  Arm64-SVE: Support scalable SIMD loads, stores, returns, and frame offsets #135944
  Arm64-SVE: Support unknown size accesses in IsContainableLclAddr #135665
  Arm64-SVE: Support Vector<T> as element of an array #133943
  Arm64-SVE: Implement Vector<T> HIR with SVE #133422
  Arm64-SVE: Add scheme for scalable SVE state in the CONTEXT record #133152
• Improve SVE codegen quality
• Address calling convention requirements
• Begin work on VL agnostic support for NativeAOT
• Improve Codegen and Performance

Support and Optimisations

• Non-SVE
  JIT: initialize tracked-local counts before liveness #134782
  Arm64: Reuse stale copy registers #136368
• SVE/SVE2
  arm64: Optimize Vector helper APIs #132117
  arm64: Reuse SVE mask constants in LSRA #131309
  arm64: Improve predicate instruction usage #129506
• Investigate using TPDiff on Arm64
• Evaluate using DynamoRIO

APIs

• Add SVE AES:Add SVE AES APIs #130859
  Add SVE AES APIs #130859

PAC and Security

• Add support for cDAC
  [cDAC] Fix incorrect filtering of stack-interior references #136089
  Arm64: [PAC-RET] cDAC changes #135959
• Support & Optimise PAC-RET
  Arm64:[PAC-RET]Fix ARM64 epilog detection and PAC signing SP recovery #135088
• Combine authenticate and return instruction using retaa
• Investigate Branch Target Identification (BTI)
• Investigate Guarded Control Stack (GCS)

Aspirational Goals

• Enable PAC-RET for .NET 12 by default

Future Architecture Features

FEAT_MOPS

• Add encodings
• Investigate use cases
  • Core libraries, such as SpanHelpers.cs
  • CoreCLR, such as CodeGen::genCodeForMemmove()

FEAT_LRCPC3

• Add encodings
• Investigate use cases
  • CacheCast checks

FEAT_CSSC

• Add encodings and optimisations

FEAT_FAMINMAX

• Add encodings and optimisations
• FEAT_SVE_LRCPC​, FEAT_SVE2p1​, FEAT_SVE2p2​, FEAT_SVE2p3​
• API Design