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xenia-rs/migration/project-root/ppc-manual/vmx/vmrghw.md
MechaCat02 e6d43a23ac 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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# `vmrghw` — Vector Merge High Word
> **Category:** [VMX (Altivec)](../categories/vmx.md) · **Form:** [VX](../forms/VX.md) · **Opcode:** `0x1000008c`
<!-- GENERATED: BEGIN -->
## Assembler Mnemonics
| Mnemonic | XML entry | Flags | Description |
| --- | --- | --- | --- |
| `vmrghw` | `vmrghw` | — | Vector Merge High Word |
| `vmrghw128` | `vmrghw128` | — | Vector128 Merge High Word |
## Syntax
```asm
vmrghw [VD], [VA], [VB]
vmrghw128 [VD], [VA], [VB]
```
## Encoding
### `vmrghw` — form `VX`
- **Opcode word:** `0x1000008c`
- **Primary opcode (bits 0–5):** `4`
- **Extended opcode:** `140`
- **Synchronising:** no
| Bits | Field | Meaning |
| --- | --- | --- |
| 0–5 | `OPCD` | primary opcode (4) |
| 6–10 | `VRT/VD` | destination vector register |
| 11–15 | `VRA/VA` | source A vector register |
| 16–20 | `VRB/VB` | source B vector register |
| 21–31 | `XO` | extended opcode (11 bits) |
### `vmrghw128` — form `VX128`
- **Opcode word:** `0x18000300`
- **Primary opcode (bits 0–5):** `6`
- **Extended opcode:** `768`
- **Synchronising:** no
| Bits | Field | Meaning |
| --- | --- | --- |
| 0–5 | `OPCD` | primary opcode (4 or 5) |
| 6–10 | `VD128l` | destination low 5 bits |
| 11–15 | `VA128l` | source A low 5 bits |
| 16–20 | `VB128l` | source B low 5 bits |
| 21 | `VA128H` | source A high bit |
| 22 | `—` | reserved |
| 23–25 | `VC` | optional VC / XO sub-field |
| 26 | `VA128h` | source A middle bit |
| 27 | `—` | reserved |
| 28–29 | `VD128h` | destination high 2 bits |
| 30–31 | `VB128h` | source B high 2 bits |
## Operands
| Field | Role | Description |
| --- | --- | --- |
| `VA` | vmrghw: read; vmrghw128: read | Source A vector register. |
| `VB` | vmrghw: read; vmrghw128: read | Source B vector register. |
| `VD` | vmrghw: write; vmrghw128: write | Destination vector register. |
## Register Effects
### `vmrghw`
- **Reads (always):** `VA`, `VB`
- **Reads (conditional):** _none_
- **Writes (always):** `VD`
- **Writes (conditional):** _none_
### `vmrghw128`
- **Reads (always):** `VA`, `VB`
- **Reads (conditional):** _none_
- **Writes (always):** `VD`
- **Writes (conditional):** _none_
## Status-Register Effects
_No condition-register or status-register effects._
## Operation (pseudocode)
```
; Pseudocode derives directly from the xenia-rs interpreter
; arm (see Implementation References). Operation semantics:
; - Read source operands from the fields listed under Operands.
; - Apply the arithmetic / logical / memory action described
; in the Description field above.
; - Write results to the destination register(s); update any
; status bits enumerated under Status-Register Effects.
; Consult the IBM AIX reference link under IBM Reference for
; canonical PPC-style pseudocode where xenia's expression is
; terse.
```
## 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
**`vmrghw`**
- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="vmrghw"`](../../xenia-canary/tools/ppc-instructions.xml)
- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_altivec.cc:989`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_altivec.cc#L989)
- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:105`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L105)
- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:451`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L451)
- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:2378-2385`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L2378-L2385)
<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
```rust
PpcOpcode::vmrghw | PpcOpcode::vmrghw128 => {
let (va, vb, vd) = vmx_reg_triple(instr);
let a = ctx.vr[va].as_u32x4();
let b = ctx.vr[vb].as_u32x4();
// Merge high words: [a0, b0, a1, b1]
ctx.vr[vd] = xenia_types::Vec128::from_u32x4(a[0], b[0], a[1], b[1]);
ctx.pc += 4;
}
```
</details>
**`vmrghw128`**
- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="vmrghw128"`](../../xenia-canary/tools/ppc-instructions.xml)
- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_altivec.cc:992`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_altivec.cc#L992)
- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:105`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L105)
- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:698`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L698)
- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:2378-2385`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L2378-L2385)
<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>
```rust
PpcOpcode::vmrghw | PpcOpcode::vmrghw128 => {
let (va, vb, vd) = vmx_reg_triple(instr);
let a = ctx.vr[va].as_u32x4();
let b = ctx.vr[vb].as_u32x4();
// Merge high words: [a0, b0, a1, b1]
ctx.vr[vd] = xenia_types::Vec128::from_u32x4(a[0], b[0], a[1], b[1]);
ctx.pc += 4;
}
```
</details>
<!-- GENERATED: END -->
## Special Cases & Edge Conditions
- **Interleave the high (most-significant) two words** of two vectors: `VD = {VA[0], VB[0], VA[1], VB[1]}`. Lane 0 (`VD[0..3]` after `stvx`) is the most-significant word.
- **Pairs with [`vmrglw`](vmrglw.md)** to cover the four words of each source. Two-instruction word-level transpose.
- **Common usage.** Interleave matrix rows during a 4×4 transpose: four `vmrgh*`/`vmrgl*` pairs swap rows and columns of a 4×4 packed-float matrix.
- **No `VSCR` interaction, no XER, no exceptions.** Pure permute.
- **Aliasing legal.** `vmrghw v3, v3, v3` doubles each high word.
- **VMX128 sibling (`vmrghw128`).** Identical semantics with the extended encoding; xenia routes via `vmx_reg_triple`.
## Related Instructions
- [`vmrglw`](vmrglw.md) — the "low half" mirror.
- [`vmrghb`](vmrghb.md), [`vmrghh`](vmrghh.md) — high-half merge at byte / half width.
- [`vperm`](vperm.md), [`vsldoi`](vsldoi.md) — programmable / static permute primitives.
- [`vupkhsh`](vupkhsh.md) — sign-extending unpack of the high half (4 halves → 4 words).
- [`vspltw`](vspltw.md) — broadcast a single word for blending tasks.
## IBM Reference
- [AIX 7.3 — `vmrghw` (Vector Merge High Word)](https://www.ibm.com/docs/en/aix/7.3.0?topic=set-vmrghw-vector-merge-high-word-instruction)
- [IBM AltiVec Technology Programmer's Interface Manual, Chapter 6 — Permute / Merge](https://www.nxp.com/docs/en/reference-manual/ALTIVECPIM.pdf)
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