riscv_opcode_tidying_operand_various

Cleaning: Allocate "Various" Operand Type

• Status: Merged for 2.41 (as a part of upstream Zfa extension work)
• Branch: riscv-opcode-tidying-operand-various
• Tracking PR: #78 (view Pull Request and Diff)
• Mailing List:
  • PATCH v1 (2022-10-25)
    • PING^1 (2022-11-16)

Feature Description

This commit intends to move operands that...

1. require very special handling or
2. operand types that are so minor (e.g. only useful on a few instructions)

under "W".

I also intend this "W" to be temporary operand storage until we can find good two character (or less) operand type.

In this commit, prefetch offset operand "f" for Zicbop extension is moved to "Wif" because of its special handling (and allocating single character "f" for this operand type seemed too much).

Current expected allocation guideline is as follows:

1. 'W'
2. The most closely related single-letter extension in lowercase (strongly recommended but not mandatory)
3. Identify operand type

The author currently plans to allocate following three-character operand types (for operands including instructions from unratified extensions).

1. "Wif" (Zicbop: fetch offset)
2. "Wfv" (unratified Zfa: value operand from FLI.[HSDQ] instructions)
3. "Wfm" / "WfM"
Zfh, F, D, Q: rounding modes "m" with special handling solely for widening conversion instructions.