[PATCH v3 0/6] Introduce extension implied rules

[frank . chang]

From: Frank Chang <frank.chang@sifive.com>

Currently, the implied extensions are enabled and checked in
riscv_cpu_validate_set_extensions(). However, the order of enabling the
implied extensions must follow a strict sequence, which is error-prone.

This patchset introduce extension implied rule helpers to enable the
implied extensions. This also eliminates the old-fashioned ordering
requirement. For example, Zvksg implies Zvks, Zvks implies Zvksed, etc.,
removing the need to check the implied rules of Zvksg before Zvks.

The idea [1] and the implied rules [2] are referenced from LLVM.

[1] 
https://github.com/llvm/llvm-project/blob/main/llvm/lib/TargetParser/RISCVISAInfo.cpp#L875
[2] 
https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/RISCV/RISCVFeatures.td

Changelog:

v3:
  - Replace the enabled bitmask of type 'uint64_t' with a dynamic bitmask
    to support more than 64 harts.
  - Ensure that implied rules and hash tables are initialized/created only once.
  - Rename variables to align nomenclature with existing variables:
      - In RISCVCPUImpliedExtsRule structure:
        - 'implied_misas' -> 'implied_misa_exts'
        - 'implied_exts' -> 'implied_multi_exts'
      - 'misa_implied_rules' -> 'misa_ext_implied_rules'
      - 'ext_implied_rules' -> 'multi_ext_implied_rules'
      - 'riscv_misa_implied_rules' -> 'riscv_misa_ext_implied_rules'
      - 'riscv_ext_implied_rules -> 'riscv_multi_ext_implied_rules'

v2:
  - Remove enabled bitmask from user-mode QEMU as there's no good way
    (e.g. mhartid) to distinguish the SMP cores in user-mode QEMU.
  - Use qatomic API to access the enabled bitmask to prevent the
    potential enabled bit from being cleared by another hart.

Frank Chang (6):
  target/riscv: Introduce extension implied rules definition
  target/riscv: Introduce extension implied rule helpers
  target/riscv: Add MISA extension implied rules
  target/riscv: Add multi extension implied rules
  target/riscv: Add Zc extension implied rule
  target/riscv: Remove extension auto-update check statements

 target/riscv/cpu.c         | 396 +++++++++++++++++++++++++++++++++++++
 target/riscv/cpu.h         |  23 +++
 target/riscv/tcg/tcg-cpu.c | 274 ++++++++++++++-----------
 3 files changed, 574 insertions(+), 119 deletions(-)

--
2.43.2