RFC ls017 Transcendental instructions for 3D and

• Funded by NLnet under the Privacy and Enhanced Trust Programme, EU Horizon2020 Grant 825310, and NGI0 Entrust No 101069594
• https://libre-soc.org/openpower/sv/rfc/ls017.transcendentals/
• https://bugs.libre-soc.org/show_bug.cgi?id=1196

Severity: Major

Status: New

Date: 29 Apr 2023

Target: v3.2B

Source: v3.1B

Books and Section affected:

    Book I Floating-Point Instructions
    Appendix E Power ISA sorted by opcode
    Appendix F Power ISA sorted by version
    Appendix G Power ISA sorted by Compliancy Subset
    Appendix H Power ISA sorted by mnemonic

Summary

    Instructions added: 43 transcendental mathematical to SFFS

Submitter: Luke Leighton (Libre-SOC)

Requester: Libre-SOC

Impact on processor:

    Addition of new Transcendental instructions

Impact on software:

    Requires support for new instructions in assembler, debuggers, and
    related tools.  Greatly decreases instruction count in 3D and HPC.

Keywords:

    Scientific Computing, HPC, 3D, OpenCL,

Motivation

Allows 3D GPU Products to be commercially viable.

Changes

Add the following entries to:

• the Appendices of Book I
• Book I 4.6.6.4 Transcendental Instructions
• Book I 1.6.1 and 1.6.2

\newpage{}

Opcode Tables for PO=59/63 XO=1---011--

Power ISA v3.1B opcodes extracted from:

• Power ISA v3.1B Appendix D Table 23 sheet 2/3 of 4 page 1391/1392
• Power ISA v3.1B Appendix D Table 25 sheet 2/3 of 4 page 1399/1400

Parenthesized entries are not part of fptrans.

• Entries whose mnemonic ends in s are only in PO=59.
• Entries whose mnemonic does not end in s are only in PO=63.
• Entries whose mnemonic ends in (s) are in both PO=59 and PO=63.

DRAFT List of 2-arg opcodes

These are X-Form, recommended Major Opcode 63 for full-width and 59 for half-width (ending in s).

Recommended 10-bit XO assignments:

DRAFT List of 1-arg transcendental opcodes

These are X-Form, and are mostly identical in Special Registers Altered to fsqrt (the exact fp exceptions they can produce differ). Recommended Major Opcode 63 for full-width and 59 for half-width (ending in s).

Special Registers Altered (FIXME: come up with correct list):

FPRF FR FI FX OX UX XX
VXSNAN VXIMZ VXZDZ
CR1                    (if Rc=1)

Recommended 10-bit XO assignments:

DRAFT List of 1-arg trigonometric opcodes

These are X-Form, and are mostly identical in Special Registers Altered to fsqrt (the exact fp exceptions they can produce differ). Recommended Major Opcode 63 for full-width and 59 for half-width (ending in s)

Special Registers Altered:

FPRF FR FI FX OX UX XX
VXSNAN VXIMZ VXZDZ
CR1                    (if Rc=1)

Recommended 10-bit XO assignments:

\newpage{}

Appendices

Appendix E Power ISA sorted by opcode
Appendix F Power ISA sorted by version
Appendix G Power ISA sorted by Compliancy Subset
Appendix H Power ISA sorted by mnemonic