chore: add migration/ bundle for cross-machine setup

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>
2026-05-10 21:38:38 +02:00
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+# `fabsx` — Floating Absolute Value
+
+> **Category:** [Floating-Point](../categories/fpu.md) · **Form:** [X](../forms/X.md) · **Opcode:** `0xfc000210`
+
+<!-- GENERATED: BEGIN -->
+
+## Assembler Mnemonics
+
+| Mnemonic | XML entry | Flags | Description |
+| --- | --- | --- | --- |
+| `fabs` | `fabsx` | — | Floating Absolute Value |
+| `fabs.` | `fabsx` | Rc=1 | Floating Absolute Value |
+
+## Syntax
+
+```asm
+fabs[Rc] [FD], [FB]
+```
+
+## Encoding
+
+### `fabsx` — form `X`
+
+- **Opcode word:** `0xfc000210`
+- **Primary opcode (bits 0–5):** `63`
+- **Extended opcode:** `264`
+- **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 |
+| --- | --- | --- |
+| `FB` | fabsx: read | Source B floating-point register. |
+| `FD` | fabsx: write | Destination floating-point register. |
+| `CR` | fabsx: write (conditional) | Condition-register update. When `Rc=1`, CR field 0 (or CR6 for vector compares, CR1 for FPU) is updated from the result. |
+
+## Register Effects
+
+### `fabsx`
+
+- **Reads (always):** `FB`
+- **Reads (conditional):** _none_
+- **Writes (always):** `FD`
+- **Writes (conditional):** `CR`
+
+## Status-Register Effects
+
+- `fabsx`: **CR0** ← signed-compare(result, 0) with `SO ← XER[SO]`, when `Rc=1`.
+
+## Operation (pseudocode)
+
+```
+FRT <- clear_sign(FRB)
+```
+
+## 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
+
+**`fabsx`**
+- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="fabsx"`](../../xenia-canary/tools/ppc-instructions.xml)
+- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_fpu.cc:478`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_fpu.cc#L478)
+- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:27`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L27)
+- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:909`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L909)
+- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:2757-2761`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L2757-L2761)
+<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
+
+```rust
+        PpcOpcode::fabsx => {
+            ctx.fpr[instr.rd()] = ctx.fpr[instr.rb()].abs();
+            if instr.rc_bit() { update_cr1_from_fpscr(ctx); }
+            ctx.pc += 4;
+        }
+```
+</details>
+
+<!-- GENERATED: END -->
+
+## Special Cases & Edge Conditions
+
+- **Bit-pattern operation, no rounding.** `fabs` clears the sign bit (bit 0) of the source FPR's binary64 representation and writes the 64-bit value to the destination unchanged otherwise. No precision loss, no FPSCR exception bits. The mnemonic does not have an `s` variant — there is one form regardless of whether the operand is interpreted as binary32 or binary64.
+- **NaN handling.** `fabs(NaN)` returns the same NaN with the sign bit cleared. The signalling/quiet bit is **not** modified, and `FPSCR[VXSNAN]` is **not** raised. xenia-rs uses `f64::abs`, which matches: it is bit-level `x & 0x7FFF_FFFF_FFFF_FFFF`.
+- **Special values.** `fabs(±0) = +0`; `fabs(±∞) = +∞`; `fabs(±NaN)` = `+NaN` (sign cleared, payload preserved).
+- **FPSCR is largely untouched.** Hardware specifies `FPRF` is **not** updated by `fabs`, and no exception bits are raised. Notation in the page header about `FPSCR` write is generic — the only meaningful write is via `Rc=1`.
+- **`Rc=1` (`fabs.`)** copies `FPSCR[FX, FEX, VX, OX]` into CR1 (these bits are typically stale or zero).
+- **No `FRA` operand.** X-form, primary 63, XO 264. Reads `FRB` only; bits 11–15 are don't-care.
+- **Common idiom.** `fabs` followed by `fcmpu` against a small constant for ULP-sized "near zero" tests; or paired with `fneg`/`fnabs` for sign-set-to-known operations.
+
+## Related Instructions
+
+- [`fnegx`](fnegx.md) — flip sign bit.
+- [`fnabsx`](fnabsx.md) — absolute value with sign **set** (always negative result).
+- [`fmrx`](fmrx.md) — copy FPR (no sign manipulation).
+- [`fselx`](fselx.md) — branch-free select; combined with `fabs` for `min`/`max`/`clamp` patterns.
+- [`fcmpux`](fcmpu.md), [`fcmpox`](fcmpo.md) — compares often paired with `fabs` for magnitude tests.
+
+## IBM Reference
+
+- [AIX 7.3 — `fabs` (Floating Absolute Value)](https://www.ibm.com/docs/en/aix/7.3.0?topic=set-fabs-floating-absolute-value-instruction)
+- [PowerISA v2.07B, Book I, Chapter 4 — Floating-Point Processor](https://openpowerfoundation.org/specifications/isa/) (sign-bit manipulation defined as bit-pattern, not arithmetic).