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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
505 changed files with 86028 additions and 0 deletions
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# `subfcx` — Subtract From Carrying
> **Category:** [Integer ALU](../categories/alu.md) · **Form:** [XO](../forms/XO.md) · **Opcode:** `0x7c000010`
<!-- GENERATED: BEGIN -->
## Assembler Mnemonics
| Mnemonic | XML entry | Flags | Description |
| --- | --- | --- | --- |
| `subfc` | `subfcx` | — | Subtract From Carrying |
| `subfco` | `subfcx` | OE=1 | Subtract From Carrying |
| `subfc.` | `subfcx` | Rc=1 | Subtract From Carrying |
| `subfco.` | `subfcx` | OE=1, Rc=1 | Subtract From Carrying |
## Syntax
```asm
subfc[OE][Rc] [RD], [RA], [RB]
```
## Encoding
### `subfcx` — form `XO`
- **Opcode word:** `0x7c000010`
- **Primary opcode (bits 0–5):** `31`
- **Extended opcode:** `8`
- **Synchronising:** no
| Bits | Field | Meaning |
| --- | --- | --- |
| 0–5 | `OPCD` | primary opcode (31) |
| 6–10 | `RT` | destination GPR |
| 11–15 | `RA` | source A |
| 16–20 | `RB` | source B |
| 21 | `OE` | overflow-enable flag |
| 22–30 | `XO` | extended opcode (9 bits) |
| 31 | `Rc` | record-form flag |
## Operands
| Field | Role | Description |
| --- | --- | --- |
| `RA` | subfcx: read | Source GPR (`r0`–`r31`). |
| `RB` | subfcx: read | Source GPR. |
| `RD` | subfcx: write | Destination GPR. |
| `CR` | subfcx: write (conditional) | Condition-register update. When `Rc=1`, CR field 0 (or CR6 for vector compares, CR1 for FPU) is updated from the result. |
| `OE` | subfcx: write (conditional) | Overflow-enable bit. When 1, the instruction updates `XER[OV]` and stickies `XER[SO]` on signed overflow. |
## Register Effects
### `subfcx`
- **Reads (always):** `RA`, `RB`
- **Reads (conditional):** _none_
- **Writes (always):** `RD`
- **Writes (conditional):** `CR`, `OE`
## Status-Register Effects
- `subfcx`: **CR0** ← signed-compare(result, 0) with `SO ← XER[SO]`, when `Rc=1`.; **XER[OV]** ← signed-overflow(result); **XER[SO]** stickies, when `OE=1`.
## Operation (pseudocode)
```
RT <- ~(RA) + (RB) + 1
CA <- carry_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
**`subfcx`**
- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="subfcx"`](../../xenia-canary/tools/ppc-instructions.xml)
- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_alu.cc:441`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_alu.cc#L441)
- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:83`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L83)
- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:859`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L859)
- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:270-287`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L270-L287)
<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
```rust
PpcOpcode::subfcx => {
// PPCBUG-007: 32-bit ABI. The `rb >= ra` u64 unsigned compare is
// exactly the shape that broke addis. Defensive 32-bit truncation
// is required for correct CA even after upstream cleanup.
let ra32 = ctx.gpr[instr.ra()] as u32;
let rb32 = ctx.gpr[instr.rb()] as u32;
let result32 = rb32.wrapping_sub(ra32);
ctx.xer_ca = if rb32 >= ra32 { 1 } else { 0 };
ctx.gpr[instr.rd()] = result32 as u64;
if instr.oe() {
let true_diff = (rb32 as i32 as i128) - (ra32 as i32 as i128);
overflow::apply(ctx, true_diff != (result32 as i32) as i128);
}
if instr.rc_bit() {
ctx.update_cr_signed(0, result32 as i32 as i64);
}
ctx.pc += 4;
}
```
</details>
<!-- GENERATED: END -->
## Special Cases & Edge Conditions
- **`RT ← RB − RA` with `XER[CA]` set on no-borrow.** Same operand-order convention as [`subfx`](subfx.md): the *first* source is subtracted *from* the second.
- **`XER[CA] = 1` means *no borrow occurred*** — i.e. `RB >= RA` as unsigned. PowerISA encodes this as the carry-out of `~RA + RB + 1`, not as a borrow flag. Xenia's `if rb >= ra` test ([`interpreter.rs:157`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L157)) is the correct boolean encoding.
- **No trap on signed overflow.** `subfco` / `subfco.` set `XER[OV]` and sticky `XER[SO]`; xenia-rs leaves the `OE` arm unimplemented.
- **64-bit CR update on Xenon, 32-bit in xenia-rs.** [`interpreter.rs:160`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L160) truncates with `as i32 as i64`. Spec demands a full 64-bit signed compare for `subfc.`.
- **Seeds a multi-word subtract chain.** Use as the low-word op; continue with [`subfex`](subfex.md) for middle words and [`subfmex`](subfmex.md)/[`subfzex`](subfzex.md) for the high word.
- **Operand aliasing fine.** `subfc r3, r3, r3` always yields `0` with `CA = 1`.
## Related Instructions
- [`subfx`](subfx.md) — same op without `XER[CA]`.
- [`subfex`](subfex.md) — `~RA + RB + CA` (chain continuation).
- [`subfmex`](subfmex.md), [`subfzex`](subfzex.md) — chain terminators.
- [`subfic`](subficx.md) — D-form: `RT ← SIMM − RA` with `XER[CA]`.
- [`addcx`](addcx.md) — dual: addition seed-of-chain.
## IBM Reference
- [AIX 7.3 — `subfc` (Subtract From Carrying)](https://www.ibm.com/docs/en/aix/7.3.0?topic=set-subfc-subtract-from-carrying-instruction)