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dedcf37867ce3a51f00e90aef2ac2948e3eab76b
Sylpheed/tools/ppc-manual/alu/oris.md
sim dedcf37867 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

4.5 KiB
Raw Blame History

oris — OR Immediate Shifted

Category: Integer ALU · Form: D · Opcode: 0x64000000

Assembler Mnemonics

Mnemonic XML entry Flags Description
oris oris — OR Immediate Shifted

Syntax

oris [RA], [RS], [UIMM]

Encoding

oris — form D

  • Opcode word: 0x64000000
  • Primary opcode (bits 0–5): 25
  • 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 oris: read Source GPR (alias for RD in some stores).
UIMM oris: read 16-bit unsigned immediate. Zero-extended.
RA oris: write Source GPR (r0–r31).

Register Effects

oris

  • 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) | (UIMM || 0x0000)

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

oris

Canary emitter (frozen snapshot @ f21ebd49e9) 
int InstrEmit_oris(PPCHIRBuilder& f, const InstrData& i) {
  // RA <- (RS) | (i32.0 || UI || i16.0)
  Value* ra =
      f.Or(f.LoadGPR(i.D.RT), f.LoadConstantUint64(XEEXTZ16(i.D.DS) << 16));
  f.StoreGPR(i.D.RA, ra);
  return 0;
}

Special Cases & Edge Conditions

  • No record form. No oris. — same as ori. For CR0 updates use orx with Rc=1.
  • Immediate is zero-extended then shifted left 16. Only bits 32–47 of RA (in PowerISA bit numbering) can be affected; the high 32 bits and low 16 bits of RA come from RS unchanged.
  • Common pair with lis to load a 32-bit constant: lis r3, hi16 (= addis r3, 0, hi16), then ori r3, r3, lo16. For unsigned constants whose low half has the high bit set, lis followed by ori works cleanly because ori is zero-extending; using addi instead would sign-extend lo16 and corrupt the constant.
  • 64-bit operation in xenia-rs. interpreter.rs:334.
  • No XER, no CR effect. Pure register OR.
  • RA = 0 reads r0 (not literal zero); see ori.

Related Instructions

  • ori — companion (immediate not shifted).
  • addis — D-form add-immediate-shifted; pairs with ori to build constants.
  • xoris, andisx — sister immediate-shifted logicals.

IBM Reference

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