# `vupkd3d128` — Vector128 Unpack D3Dtype

> **Category:** [VMX128](../categories/vmx128.md) · **Form:** [VX128_3](../forms/VX128_3.md) · **Opcode:** `0x180007f0`

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## Assembler Mnemonics

| Mnemonic | XML entry | Flags | Description |
| --- | --- | --- | --- |
| `vupkd3d128` | `vupkd3d128` | — | Vector128 Unpack D3Dtype |

## Syntax

```asm
(no disassembly template)
```

## Encoding

### `vupkd3d128` — form `VX128_3`

- **Opcode word:** `0x180007f0`
- **Primary opcode (bits 0–5):** `6`
- **Extended opcode:** `2032`
- **Synchronising:** no

| Bits | Field | Meaning |
| --- | --- | --- |
| 0–5 | `OPCD` | primary opcode (6) |
| 6–10 | `VD128l` | destination low 5 bits |
| 11–15 | `IMM` | 5-bit immediate |
| 16–20 | `VB128l` | source B low 5 bits |
| 21–27 | `XO` | extended opcode |
| 28–29 | `VD128h` | destination high 2 bits |
| 30–31 | `VB128h` | source B high 2 bits |

## Operands

| Field | Role | Description |
| --- | --- | --- |
| `VB` | vupkd3d128: read | Source B vector register. |
| `VD` | vupkd3d128: write | Destination vector register. |

## Register Effects

### `vupkd3d128`

- **Reads (always):** `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

**`vupkd3d128`**
- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="vupkd3d128"`](../../xenia-canary/tools/ppc-instructions.xml)
- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_altivec.cc:2194`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_altivec.cc#L2194)
- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:128`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L128)
- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:670`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L670)
- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:4249-4275`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L4249-L4275)
<details><summary>xenia-rs interpreter body (frozen snapshot)</summary>

```rust
        PpcOpcode::vupkd3d128 => {
            use crate::vmx::D3dPackType;
            let uimm = crate::decoder::extract_vx128_uimm5(instr.raw);
            let ty = D3dPackType::from_immediate(uimm >> 2);
            let src = ctx.vr[instr.vb128()];
            let out = match ty {
                D3dPackType::D3dColor     => crate::vmx::unpack_d3dcolor(src),
                D3dPackType::NormShort2   => crate::vmx::unpack_normshort2(src),
                D3dPackType::NormPacked32 => crate::vmx::unpack_normpacked32(src),
                D3dPackType::Float16_2    => crate::vmx::unpack_float16_2(src),
                D3dPackType::NormShort4   => crate::vmx::unpack_normshort4(src),
                D3dPackType::Float16_4    => crate::vmx::unpack_float16_4(src),
                D3dPackType::NormPacked64 => crate::vmx::unpack_normpacked64(src),
                D3dPackType::Other(t)     => {
                    tracing::warn!(
                        raw = format_args!("{:#010x}", instr.raw),
                        uimm,
                        ty = t,
                        "vupkd3d128: unhandled pack type at {:#010x}",
                        ctx.pc,
                    );
                    src
                }
            };
            ctx.vr[instr.vd128()] = out;
            ctx.pc += 4;
        }
```
</details>

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## Special Cases & Edge Conditions

- **Unpack a D3D-format word into 4 float lanes.** The `IMM` field in the encoding selects the target format:
  - `D3dColor` — decode a 32-bit RGBA8 (`D3DCOLOR`) into 4 float lanes in `[0.0, 1.0]`. Xenia's helper is `vmx::unpack_d3dcolor`.
  - Other formats (UBYTE4N, SHORT2N, etc.) are not yet implemented in xenia-rs; the interpreter logs a warning and passes `VB` through unchanged.
- **Inverse of [`vpkd3d128`](vpkd3d128.md).** The same format code used to pack must be used to unpack.
- **Source-width is a single 32-bit word** of `VB` (typically lane 0; the helpers read the appropriate component). The other three input word lanes are ignored for `D3DCOLOR`.
- **IEEE-754 binary32 outputs,** already normalised to `[0.0, 1.0]` (integer value divided by 255, then cast to float).
- **No `VSCR[SAT]` effect**, no FPSCR, no exceptions.
- **VMX128 register-fusion** on `VD` and `VB`.
- **No IBM AIX entry** — Xenon-only.
- **No `Rc`, no XER.**

## Related Instructions

- [`vpkd3d128`](vpkd3d128.md) — the inverse pack.
- [`vupkhpx`](../vmx/vupkhpx.md), [`vupklpx`](../vmx/vupklpx.md) — standard Altivec 1-5-5-5 pixel unpacks.
- [`vupkhsb`](../vmx/vupkhsb.md), [`vupklsb`](../vmx/vupklsb.md) — sign-extending byte→half-word unpacks (the integer analogue).
- [`vcsxwfp128`](vcsxwfp128.md), [`vcuxwfp128`](vcuxwfp128.md) — int → float with scale; sometimes used as an alternate decode path.

## IBM Reference

- No IBM AIX entry — Xbox 360 VMX128 extension only. "D3D" denotes the Direct3D 9 vertex/pixel format catalogue (`D3DDECLTYPE_*`).
- Xbox 360 XDK, Altivec-128 (VMX128) extensions.
- Microsoft D3D9 documentation: `D3DDECLTYPE_D3DCOLOR`, `D3DDECLTYPE_UBYTE4N`, etc.