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chore: add migration/ bundle for cross-machine setup

Browse Source 
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>
This commit is contained in:
MechaCat02
2026-05-10 21:38:38 +02:00
parent 8e709b0a24
commit e6d43a23ac
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# `srawix` — Shift Right Algebraic Word Immediate
> **Category:** [Integer ALU](../categories/alu.md) · **Form:** [X](../forms/X.md) · **Opcode:** `0x7c000670`
<!-- GENERATED: BEGIN -->
## Assembler Mnemonics
| Mnemonic | XML entry | Flags | Description |
| --- | --- | --- | --- |
| `srawi` | `srawix` | — | Shift Right Algebraic Word Immediate |
| `srawi.` | `srawix` | Rc=1 | Shift Right Algebraic Word Immediate |
## Syntax
```asm
srawi[Rc] [RA], [RS], [SH]
```
## Encoding
### `srawix` — form `X`
- **Opcode word:** `0x7c000670`
- **Primary opcode (bits 0–5):** `31`
- **Extended opcode:** `824`
- **Synchronising:** no
| Bits | Field | Meaning |
| --- | --- | --- |
| 0–5 | `OPCD` | primary opcode |
| 6–10 | `RT/FRT/VRT` | destination |
| 11–15 | `RA/FRA/VRA` | source A |
| 16–20 | `RB/FRB/VRB` | source B |
| 21–30 | `XO` | extended opcode (10 bits) |
| 31 | `Rc` | record-form flag |
## Operands
| Field | Role | Description |
| --- | --- | --- |
| `RS` | srawix: read | Source GPR (alias for RD in some stores). |
| `SH` | srawix: read | Shift amount. |
| `RA` | srawix: write | Source GPR (`r0`–`r31`). |
| `CR` | srawix: write (conditional) | Condition-register update. When `Rc=1`, CR field 0 (or CR6 for vector compares, CR1 for FPU) is updated from the result. |
| `CA` | srawix: write | XER[CA] carry bit. Read by add-with-carry/subtract-with-borrow instructions, written by carrying instructions. |
## Register Effects
### `srawix`
- **Reads (always):** `RS`, `SH`
- **Reads (conditional):** _none_
- **Writes (always):** `RA`, `CA`
- **Writes (conditional):** `CR`
## Status-Register Effects
- `srawix`: **CR0** ← signed-compare(result, 0) with `SO ← XER[SO]`, when `Rc=1`.; **XER[CA]** ← carry-out of the add / borrow-in of the subtract (always).
## Operation (pseudocode)
```
RA <- ((RS)[32:63] >>a SH) sign-extended
CA <- (RS[32] signed) && any_low_bit_shifted_out
```
## C Translation Example
```c
/* C translation: the xenia-rs interpreter arm below in */
/* Implementation References is the authoritative semantic */
/* snapshot. Translate it line-by-line: */
/* - ctx.gpr[N] -> r[N] (or f[]/v[] for FPRs/VRs) */
/* - mem.read_u*/write_u* -> mem_read_u*_be / mem_write_u*_be */
/* - ctx.update_cr_signed(fld, v) -> update_cr_signed(fld, v) */
/* - ctx.xer_ca / xer_ov / xer_so -> xer.CA / xer.OV / xer.SO */
/* The Register Effects and Status-Register Effects tables above */
/* enumerate every side effect a faithful translation must emit. */
```
## Implementation References
**`srawix`**
- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="srawix"`](../../xenia-canary/tools/ppc-instructions.xml)
- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_alu.cc:1291`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_alu.cc#L1291)
- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:65`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L65)
- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:843`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L843)
- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:661-675`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L661-L675)
<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
```rust
PpcOpcode::srawix => {
// PPCBUG-042+043 coupled: same shape as srawx for the sh-immediate form.
let rs = ctx.gpr[instr.rs()] as i32;
let sh = instr.sh();
if sh == 0 {
ctx.gpr[instr.ra()] = rs as u32 as u64;
ctx.xer_ca = 0;
} else {
let result = rs >> sh;
ctx.xer_ca = if rs < 0 && (rs as u32) << (32 - sh) != 0 { 1 } else { 0 };
ctx.gpr[instr.ra()] = result as u32 as u64;
}
if instr.rc_bit() { ctx.update_cr_signed(0, ctx.gpr[instr.ra()] as u32 as i32 as i64); }
ctx.pc += 4;
}
```
</details>
<!-- GENERATED: END -->
## Special Cases & Edge Conditions
- **`RA ← ((i32)RS >> SH) sign-extended`** with `XER[CA]` set when `RS` is negative AND any low bit was shifted out.
- **`SH` is 5 bits** (immediate, range `0..31`). Unlike [`srawx`](srawx.md), there is no saturation case because the count cannot exceed 31. Xenia reads it via `instr.sh()`.
- **`SH = 0`** sign-extends `RS[32:63]` to 64 bits and clears `CA`. This is *not* a no-op when `RS`'s high 32 bits differ from the sign extension of bit 32.
- **Common idiom: `srawi rA, rS, 31`** materialises the 32-bit sign of `rS` as `0` or `−1` — the canonical "sign mask" pattern. Often used for branchless `abs` or conditional negation.
- **Idiom: `srawi rA, rS, n; addze rA, rA`** — divide signed by `2^n` rounding toward zero.
- **`Rc=1` CR0 update truncates to 32 bits in xenia-rs.** [`interpreter.rs:457`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L457) — matches spec because the sign-extended result has consistent low/high 32-bit signs.
- **No `OE` bit.**
## Related Instructions
- [`srawx`](srawx.md) — register-shift form.
- [`sradix`](sradix.md), [`sradx`](sradx.md) — 64-bit arithmetic right.
- [`addzex`](addzex.md) — divide-rounding companion.
- [`extswx`](extswx.md) — `srawi rA, rS, 0` is functionally a sign-extend-32-to-64 plus `CA = 0` clear; `extsw` is preferred when CA isn't wanted.
## IBM Reference
- [AIX 7.3 — `srawi` (Shift Right Algebraic Word Immediate)](https://www.ibm.com/docs/en/aix/7.3.0?topic=set-srawi-shift-right-algebraic-word-immediate-instruction)