Book E and PPC 440

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Difference of Book-E and PPC440 insn


Introduction

This document would make clear differences of Book-E defined instructions and PPC440 implementation to maintain BINUTILS opcode table for Book-E, PPC440 and other Book-E based embedded processors

For this purpose, we don't mention about 64bit operations which PPC440 and most embedded processor don't support. Also we don't mention about differences of registers, like Special Purpose Registers (SPRs).

Section 2 would make clear where Book-E does cover and where it doesn't. Section 3 identifies what Book-E instructions are not supported in PPC440, implementation-dependent operands/ variants. Final section describes PPC440 allocated instructions.


Book-E coverage

In Book-E, PPC Instructions are classified as following;

    Book-E defined    - defined and described in Book-E;
              (Very few instruction may have
              implementation-dependent variant
              and/or operands)
    preserved    - for classic PPC use
    reserved    - for future use
    allocated    - for implementation-dependent use


E.g. For PPC440 implementation, Section 5, "Instruction Set", in 440_Programming_Model.pdf shows instruction categories at "Table 4 - PowerPC 440 Instruction Categories".

In general, the Book-E provides for allocated instructions, which are instructions available for implementation-dependent and/or application-specific purposes. Those allocated instructions will be described in processor's manual.

Section 9.1 "Instruction Set Portability", in 440x4_um.pdf, mentions allocated instructions of PPC440 core and "Table 9-2. Allocated Instructions" shows list of the allocated instructions. Due to 440x4_um.pdf, allocated instructions of PPC440 core are not PPC440 specific, common extension for IBM PPC400 embedded series.

Even in the Book-E defined instructions, not in allocated class instructions, there are some implementation-dependent variation. For example, tlbre/tlbwe instructions are defined in the Book-E, may have implementation-dependent operands.

Due to results of searching "implementation-dependent" word from the Book-E instruction set descriptions, Following instructions have implementation-dependent field. In other words, following instructions may have implementation-dependent variants and/or operands.


  • Data Cache Block Touch {{{

dcbt[e] CT,RA,RB

   This may have implementation-dependent variants and/or
   operands.
   CT (6:10)    This field used by the Cache Touch instructions
   (dcbt[e], dcbtst[e], and icbt[e]) to specify the target
   portion of the cache facility to place the pre-fetched data or
   instructions and is implementation-dependent.

}}}

  • Data Cache Block Touch for Store {{{

dcbtst[e] CT,RA,RB

   This may have implementation-dependent variants and/or
   operands.
   CT means same as above.

}}}

  • Instruction Cache Block Touch {{{

icbt[e] CT,RA,RB

   This may have implementation-dependent variants and/or
   operands.
   CT means same as above.

}}}

  • TLB Read Entry {{{

tlbre

   This may have implementation-dependent variants and/or
   operands.
   Bits 6:20 of the instruction encoding are allocated for
   implementation-dependent use, and may be used to specify
   the source TLB entry, the source portion of the source
   TLB entry, and the target resource that the result is
   placed into.

}}}

  • TLB Search Indexed [Extended] {{{

tlbsx[e] RA,RB

   This may have implementation-dependent variants and/or
   operands.
   Bits 6:10 of the instruction encoding are allocated for
   implementation-dependent use, and may be used to specify
   the target resource that the result of the instruction
   is placed into.

}}}

  • TLB Write Entry {{{

tlbwe

   This may have implementation-dependent variants and/or
   operands.
   Bits 6:20 of the instruction encoding are allocated for
   implementation-dependent use, and may be used to specify
   the target TLB entry, the target portion of the target
   TLB entry, and the source of the value that is to be
    written into the TLB.

}}}

PPC440 variants/limitations of Book-E defined instructions

PPC440 limitations

This subsection shows intructions which BOOK-E defines but PPC440 doesn't implement.

"2.3.1 Defined Instruction Class" in 440x4_um.pdf, says PPC440 doesn't support following Book-E defined instructions;

    tlbivax[e]
    mfapidi
    64bit operations
    floating-point operations

The first two instructions and 64bit operations are treated as illegal Instruction. PPC440 core doesn't support floating-point operations inside it, however attached auxiliary processor may support them. Without such auxiliary processor, floating-point operations are treated as illegal instruction.

PPC440 variants

This subsection shows intructions which both BOOK-E and PPC440 defines but PPC440 implement slightly diffrent ways.

Book-E defines following TLB management instructions;

    tlbivax[e]    RA,RB    TLB Invalidate Virtual Address
                    Indexed (Extended)
    tlbre            TLB Read Entry
    tlbsx[e]    RA,RB    TLB Search Indexed (Extended)
    tlbsync        TLB Synchronize
    tlbwe            TLB Write Entry

440x4_um.pdf shows following TLB management instructions.

    tlbre        RT, RA, WS
    tlbsx[.]    RT, RA, RB
    tlbsync
    tlbwe        RS, RA, WS

Book-E defines following cache block touch instructions;

    dcbt[e]        CT,RA,RB    Data Cache Block Touch
    dcbtst[e]    CT,RA,RB    Data Cache Block Touch for Store
    icbt[e]        CT,RA,RB    Instruction Cache Block Touch
        CT means implementation-dependent operand.

However, 440x4_um.pdf says PPC440 have following;

    dcbt        RA,RB
    dcbst        RA,RB
    icbt        RA,RB

In addition, as a special case, icbt instruction have two opcodes. One is one of allocated opcode (primary:31, secondary:262) for keeping compatibility with previous PPC400 Series. The other is one of Book-E defined opcode (primary:31, secondary:22), because icbt is now part of Book-E.


PPC440 allocated instructions

Allocated Arithmetic

Those instructions support multiply-accumulate, negative multiply-accumulate and multiply halfword.

Multiply-Accumulate

    macchw[o][.]          RT,RA,RB
    macchws[o][.]        RT,RA,RB
    macchwsu[o][.]    RT,RA,RB
    macchwu[o][.]     RT,RA,RB
    machhw[o][.]          RT,RA,RB
    machhws[o][.]     RT,RA,RB
    machhwsu[o][.]     RT,RA,RB
    machhwu[o][.]     RT,RA,RB
    maclhw[o][.]          RT,RA,RB
    maclhws[o][.]     RT,RA,RB
    maclhwsu[o][.]     RT,RA,RB
    maclhwu[o][.]     RT,RA,RB


Negative Multiply-Accumulate

    nmacchw[o][.]     RT,RA,RB
    nmacchws[o][.]     RT,RA,RB
    nmachhw[o][.]     RT,RA,RB
    nmachhws[o][.]     RT,RA,RB
    nmaclhw[o][.]     RT,RA,RB
    nmaclhws[o][.]     RT,RA,RB


Multiply-Halfword

    mulchw[.]      RT,RA,RB
    mulchwu[.]      RT,RA,RB
    mulhhw[.]      RT,RA,RB
    mulhhwu[.]      RT,RA,RB
    mullhw[.]      RT,RA,RB
    mullhwu[.]      RT,RA,RB


Allocated Logical

This instructions detects left-most zero byte, is helpful for implementing function like strlen().

    dlmzb[.]    RA,RS,RB


Allocated Cache Management

These instructions flash invalidate entire data/instruction cache array.

    dccci        RA,RB
    iccci        RA,RB


Allocated Cache Debug

These instructions read data/instruction cache

    dcread        RT,RA,RB
    icread        RA,RB


Appendix References

  • 440_Programing_Model.pdf
   IBM PowerPC(TM) 440 Microprocessor Core Programming Model Overview    
   October 4,2001
  • 440x4_um.pdf
   PPC440 CPU Core Users Manual
   SA14-2523-02 July 18, 2002
  • booke_rm.pdf
   Book E: Enhanced PowerPC(TM) Architecture
   Version 1.0 May 7, 2002