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docs(ppc-manual): quote Canary and our own decoder, not the retired xenia-rs 
The generator had not been able to run correctly since the manual moved into
`tools/ppc-manual/`: it computed the repository root as `HERE.parent.parent`,
which now names `tools/`, so the XML, Canary's emitters and xenia-rs all stopped
resolving — silently, because both scrapers skipped what they could not find.
Every page's references had been pointing at paths that exist nowhere.

What each source contributed, measured on the 350 pages before this change:

  Operation (pseudocode)  251 pages: fixed boilerplate "derives from the xenia-rs
                          interpreter"; 99 carry real hand-written seeds
  C translation           337 pages: the same kind of boilerplate
  xenia-rs snapshot       336 pages: the interpreter arm, pasted in — the only
                          per-instruction semantics on unseeded pages
  links                   xenia-rs opcode/decoder/interpreter + Canary emitter

Now:

  * semantics come from **Xenia Canary**, the reference emulator, read through
    `git show` at a pinned upstream commit (`origin/canary_experimental`,
    f21ebd49e9). Not our checkout: it carries instrumentation and lacked
    upstream's `mcrf` fix, so it would have published probes and a wrong `mcrf`.
    Each page embeds the emitter (`InstrEmit_<mnem>`), and for the 128 pure
    one-line delegations also the helper that holds the semantics.
  * decode references point at `crates/sylpheed-ppc` — the decoder that
    produces `sylpheed.db` — as in-repo relative links.
  * the boilerplate now says what is true, and the C translation guide maps
    Canary's actual HIR calls, checked against `ppc_hir_builder.h` (including
    that `UpdateCR(n, v)` truncates to 32 bits).
  * `rust_scraper.py` -> `decoder_scraper.py` (interpreter half dropped);
    missing sources are now errors, not empty results.

Verified:

  consistency checks        455 XML entries, 350 families, 598 index keys
  hand-written tails        386/386 byte-identical after regeneration
  xenia-rs in generated     0
  pages with a snapshot     349/350 (was 336) — `dcbi` has no Canary emitter at all
  in-repo decoder links     910/910 resolve to a line holding the identifier
  emitter boundaries        brace counter == column-0 `}` rule on 521/521;
                            preprocessor model unit-tested (#if 0/#else/#elif)
  idempotency               re-run: 0 pages updated, 0 working-tree changes

Hand-written notes (outside the generated regions) are not rewritten here:

  * 110 links into `../../xenia-rs/...` were dead; they now point at the file in
    the archived repository (git.mc02.dev/fabi/xenia-rs @ 8401d4d). Line anchors
    were dropped because the notes predate that commit — 0 of 441 old line
    ranges match it — and a precise-looking wrong anchor is worse than none. The
    link text, which carries the author's line numbers, is unchanged.
  * 140 prose claims about xenia-rs's behaviour remain. 23 are verified to hold
    for Canary too (the 32-bit CR0 truncation, OE left unimplemented); the other
    114 need checking one by one, and some invert — e.g. `divdx` notes a correct
    64-bit CR0 update in xenia-rs where Canary's `UpdateCR` truncates. Left for
    a deliberate pass rather than a blind substitution.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-09-16 20:34:34 +02:00

4.4 KiB
Raw Blame History

xori — XOR Immediate

Category: Integer ALU · Form: D · Opcode: 0x68000000

Assembler Mnemonics

Mnemonic XML entry Flags Description
xori xori — XOR Immediate

Syntax

xori [RA], [RS], [UIMM]

Encoding

xori — form D

  • Opcode word: 0x68000000
  • Primary opcode (bits 0–5): 26
  • Extended opcode: —
  • Synchronising: no
Bits Field Meaning
0–5 OPCD primary opcode
6–10 RT destination GPR (or RS when storing)
11–15 RA source GPR (0 ⇒ literal 0 for RA0 forms)
16–31 D/SI/UI 16-bit signed or unsigned immediate

Operands

Field Role Description
RS xori: read Source GPR (alias for RD in some stores).
UIMM xori: read 16-bit unsigned immediate. Zero-extended.
RA xori: write Source GPR (r0–r31).

Register Effects

xori

  • Reads (always): RS, UIMM
  • Reads (conditional): none
  • Writes (always): RA
  • Writes (conditional): none

Status-Register Effects

No condition-register or status-register effects.

Operation (pseudocode)

RA <- (RS) ^ (0x0000 || UIMM)

C Translation Example

/* No hand-written C yet. Translate the Canary emitter snapshot   */
/* under Implementation References; its HIR maps directly:        */
/*   f.LoadGPR(n) / f.StoreGPR(n, v)  -> r[n] / r[n] = v          */
/*   f.LoadFPR / StoreFPR, f.LoadVR / StoreVR -> f[n], v[n]        */
/*   f.Load(ea, T), f.Store(ea, v) -> raw read / write; emitters   */
/*     wrap them in f.ByteSwap for the big-endian guest value      */
/*   f.UpdateCR(n, v)  -> CR field n from v's LOW 32 BITS vs 0     */
/*   f.LoadCA / f.StoreCA -> xer.CA;  f.StoreSAT -> vscr.SAT       */
/*   i.XO.RA, i.D.DS, ... -> the bit-fields listed under Operands  */
/* The Register Effects and Status-Register Effects tables above  */
/* enumerate every side effect a faithful translation must emit.  */

Implementation References

xori

Canary emitter (frozen snapshot @ f21ebd49e9) 
int InstrEmit_xori(PPCHIRBuilder& f, const InstrData& i) {
  // RA <- (RS) XOR (i48.0 || UI)
  Value* ra = f.Xor(f.LoadGPR(i.D.RT), f.LoadConstantUint64(XEEXTZ16(i.D.DS)));
  f.StoreGPR(i.D.RA, ra);
  return 0;
}

Special Cases & Edge Conditions

  • No record form. Like ori, there is no xori.. To get a CR0 update follow with cmpwi or use xorx with Rc=1.
  • Immediate is zero-extended to 64 bits. Only the low 16 bits of RA can be flipped; the high 48 bits are passed through from RS unchanged.
  • xori 0, 0, 0 is a valid NOP encoding but the canonical NOP is ori 0, 0, 0. Disassemblers should still display this as xori r0, r0, 0 or recognise it as a no-op.
  • 64-bit operation in xenia-rs. interpreter.rs:338 — full u64 XOR with the immediate.
  • No XER, no CR side effects.
  • RA = 0 reads r0 (not literal zero); see ori.
  • Useful for masked toggle. xori rA, rS, mask flips the bits of rS indicated by mask (low 16 bits only).

Related Instructions

  • xoris — companion (immediate shifted left 16).
  • xorx — register-register XOR.
  • eqvx — ~(RS ^ RB).
  • ori, andix — sister immediate logicals.

IBM Reference

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