e6d43a23ac
Bundles state that lives OUTSIDE the xenia-rs repo so a fresh clone on
another machine can be brought up to identical configuration via
migration/setup.sh:
- claude-memory/ ~/.claude/projects/-home-fabi-RE-Project-Sylpheed/memory/
(103 files, 1.1 MB - MEMORY.md + every
project_xenia_rs_*.md from audits
addis_signext through audit-058)
- project-root/dot-claude/ <project-root>/.claude/settings.json
(Stop hook + permissions)
- project-root/ppc-manual/ <project-root>/ppc-manual/
(PowerPC reference docs, 397 files, 3.7 MB)
- project-root/run-canary.sh <project-root>/run-canary.sh
- README.md Human-readable setup checklist
- setup.sh Idempotent installer (also reclones
xenia-canary at pinned HEAD 6de80dffe)
- MANIFEST.md Per-file mapping + per-file-not-bundled
restoration recipe
Excluded from bundle (not shippable via git):
- Sylpheed ISO (7.8 GB; copyright; manual copy required)
- sylpheed.db (395 MB; regenerable from XEX via analysis tooling)
- target/ build artifacts (rebuild on target)
- audit-runs probe firehoses (.log/.stdout/.stderr ~11 GB; rerun if needed)
- audit-runs memory dumps (.bin ~4.5 GB; rerun audit-026/027/029 if needed)
- xenia-canary checkout (setup.sh reclones from
git.mc02.dev/fabi/Xenia-Canary.git at HEAD 6de80dffe)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
125 lines
4.9 KiB
Markdown
125 lines
4.9 KiB
Markdown
# `creqv` — Condition Register Equivalent
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> **Category:** [Control / CR / SPR](../categories/control.md) · **Form:** [XL](../forms/XL.md) · **Opcode:** `0x4c000242`
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<!-- GENERATED: BEGIN -->
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## Assembler Mnemonics
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| Mnemonic | XML entry | Flags | Description |
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| --- | --- | --- | --- |
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| `creqv` | `creqv` | — | Condition Register Equivalent |
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## Syntax
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```asm
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creqv [CRBD], [CRBA], [CRBB]
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```
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## Encoding
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### `creqv` — form `XL`
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- **Opcode word:** `0x4c000242`
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- **Primary opcode (bits 0–5):** `19`
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- **Extended opcode:** `289`
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- **Synchronising:** no
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| Bits | Field | Meaning |
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| --- | --- | --- |
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| 0–5 | `OPCD` | primary opcode (19) |
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| 6–10 | `BT/BO` | target / branch options |
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| 11–15 | `BA/BI` | source A / CR bit to test |
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| 16–20 | `BB` | source B |
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| 21–30 | `XO` | extended opcode (10 bits) |
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| 31 | `LK` | link flag |
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## Operands
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| Field | Role | Description |
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| --- | --- | --- |
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| `CRBA` | creqv: read | CR source bit A (0–31). |
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| `CRBB` | creqv: read | CR source bit B (0–31). |
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| `CRBD` | creqv: write | CR destination bit (0–31). |
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## Register Effects
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### `creqv`
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- **Reads (always):** `CRBA`, `CRBB`
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- **Reads (conditional):** _none_
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- **Writes (always):** `CRBD`
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- **Writes (conditional):** _none_
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## Status-Register Effects
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_No condition-register or status-register effects._
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## Operation (pseudocode)
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```
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; Pseudocode derives directly from the xenia-rs interpreter
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; arm (see Implementation References). Operation semantics:
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; - Read source operands from the fields listed under Operands.
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; - Apply the arithmetic / logical / memory action described
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; in the Description field above.
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; - Write results to the destination register(s); update any
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; status bits enumerated under Status-Register Effects.
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; Consult the IBM AIX reference link under IBM Reference for
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; canonical PPC-style pseudocode where xenia's expression is
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; terse.
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```
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## C Translation Example
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```c
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/* C translation: the xenia-rs interpreter arm below in */
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/* Implementation References is the authoritative semantic */
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/* snapshot. Translate it line-by-line: */
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/* - ctx.gpr[N] -> r[N] (or f[]/v[] for FPRs/VRs) */
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/* - mem.read_u*/write_u* -> mem_read_u*_be / mem_write_u*_be */
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/* - ctx.update_cr_signed(fld, v) -> update_cr_signed(fld, v) */
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/* - ctx.xer_ca / xer_ov / xer_so -> xer.CA / xer.OV / xer.SO */
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/* The Register Effects and Status-Register Effects tables above */
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/* enumerate every side effect a faithful translation must emit. */
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```
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## Implementation References
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**`creqv`**
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- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="creqv"`](../../xenia-canary/tools/ppc-instructions.xml)
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- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_control.cc:370`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_control.cc#L370)
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- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:17`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L17)
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- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:718`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L718)
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<!-- GENERATED: END -->
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## Special Cases & Edge Conditions
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- **Operation.** `CR[CRBD] ← ¬(CR[CRBA] XOR CR[CRBB])` — i.e. logical equivalence (XNOR). Result is 1 iff `CRBA` and `CRBB` agree.
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- **`crset BT` idiom.** With identical operands, `creqv BT, BT, BT` always yields 1 (any bit XNOR'd with itself is 1). This is the canonical PowerPC **set-to-1** for a single CR bit; assemblers recognise the simplified mnemonic `crset BT`.
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- **Bit-level operands.** Like all CR-logical ops, the three operands are 5-bit absolute CR-bit indices (0..31). Mixing CR fields is fine.
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- **Use case.** Branch on "A == B" of two prior compare results. Example: `crxor` of CR0.SO and CR1.SO gives "differ"; `creqv` gives "agree".
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- **No `Rc` / `OE`.** Doesn't touch CR0, XER, or any other state beyond the named bit.
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- **Not synchronising.** Reorderable.
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- **xenia status.** Interpreter dispatches through the generic CR-logical helper; canary emits the host XNOR equivalent. The `crset` simplified form is the most common occurrence in real Xbox 360 code.
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## Related Instructions
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- [`crand`](crand.md), [`crandc`](crandc.md) — AND family.
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- [`cror`](cror.md), [`crorc`](crorc.md), [`crnor`](crnor.md), [`crnand`](crnand.md) — OR family.
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- [`crxor`](crxor.md) — the dual; `crxor BT, BT, BT` is the standard **clear-to-0** idiom.
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- [`mcrf`](mcrf.md) — bulk CR-field move.
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- [`bcx`](../branch/bcx.md) — consumes the synthesised bit.
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### Simplified Mnemonics
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| Simplified | Expansion | Effect |
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| --- | --- | --- |
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| `crset BT` | `creqv BT, BT, BT` | force `CR[BT] ← 1` |
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## IBM Reference
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- [AIX 7.3 — `creqv` (Condition Register Equivalent)](https://www.ibm.com/docs/en/aix/7.3.0?topic=set-creqv-condition-register-equivalent-instruction)
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- [AIX 7.3 — Condition register simplified mnemonics](https://www.ibm.com/docs/en/aix/7.3.0?topic=mnemonics-condition-register-logical-simplified)
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