# `lvewx` — Load Vector Element Word Indexed
> **Category:** [Memory](../categories/memory.md) · **Form:** [X](../forms/X.md) · **Opcode:** `0x7c00008e`
## Assembler Mnemonics
| Mnemonic | XML entry | Flags | Description |
| --- | --- | --- | --- |
| `lvewx` | `lvewx` | — | Load Vector Element Word Indexed |
| `lvewx128` | `lvewx128` | — | Load Vector Element Word Indexed 128 |
## Syntax
```asm
lvewx [VD], [RA0], [RB]
lvewx128 [VD], [RA0], [RB]
```
## Encoding
### `lvewx` — form `X`
- **Opcode word:** `0x7c00008e`
- **Primary opcode (bits 0–5):** `31`
- **Extended opcode:** `71`
- **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 |
### `lvewx128` — form `VX128_1`
- **Opcode word:** `0x10000083`
- **Primary opcode (bits 0–5):** `4`
- **Extended opcode:** `131`
- **Synchronising:** no
| Bits | Field | Meaning |
| --- | --- | --- |
| 0–5 | `OPCD` | primary opcode (4) |
| 6–10 | `VD128l` | destination low 5 bits |
| 11–15 | `RA` | address register |
| 16–20 | `RB` | offset register |
| 21–27 | `XO` | extended opcode |
| 28–29 | `VD128h` | destination high 2 bits |
| 30–31 | `—` | reserved |
## Operands
| Field | Role | Description |
| --- | --- | --- |
| `RA0` | lvewx: read; lvewx128: read | Source GPR; when the encoded register number is 0 the operand is the literal 64-bit zero, **not** `r0`. |
| `RB` | lvewx: read; lvewx128: read | Source GPR. |
| `VD` | lvewx: write; lvewx128: write | Destination vector register. |
## Register Effects
### `lvewx`
- **Reads (always):** `RA0`, `RB`
- **Reads (conditional):** _none_
- **Writes (always):** `VD`
- **Writes (conditional):** _none_
### `lvewx128`
- **Reads (always):** `RA0`, `RB`
- **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
**`lvewx`**
- xenia-canary XML: [`tools/ppc-instructions.xml` — search for `mnem="lvewx"`](../../xenia-canary/tools/ppc-instructions.xml)
- xenia-canary emit: [`src/xenia/cpu/ppc/ppc_emit_altivec.cc:96`](../../xenia-canary/src/xenia/cpu/ppc/ppc_emit_altivec.cc#L96)
- xenia-rs opcode: [`crates/xenia-cpu/src/opcode.rs:44`](../../xenia-rs/crates/xenia-cpu/src/opcode.rs#L44)
- xenia-rs decoder: [`crates/xenia-cpu/src/decoder.rs:770`](../../xenia-rs/crates/xenia-cpu/src/decoder.rs#L770)
- xenia-rs interpreter: [`crates/xenia-cpu/src/interpreter.rs:1898-1913`](../../xenia-rs/crates/xenia-cpu/src/interpreter.rs#L1898-L1913)
xenia-rs interpreter body (frozen snapshot)
```rust
PpcOpcode::lvewx => {
// Load a word from (EA & ~3) into vD at word slot
// (EA & 0xF) >> 2. Other word lanes preserved (see lvebx).
let base = if instr.ra() == 0 { 0u64 } else { ctx.gpr[instr.ra()] };
let ea_unaligned = base.wrapping_add(ctx.gpr[instr.rb()]) as u32;
let ea = ea_unaligned & !0x3u32;
let slot = ((ea_unaligned & 0xF) >> 2) as usize;
let mut bytes = ctx.vr[instr.rd()].as_bytes();
let w = mem.read_u32(ea);
bytes[slot * 4] = (w >> 24) as u8;
bytes[slot * 4 + 1] = (w >> 16) as u8;
bytes[slot * 4 + 2] = (w >> 8) as u8;
bytes[slot * 4 + 3] = (w & 0xFF) as u8;
ctx.vr[instr.rd()] = xenia_types::Vec128::from_bytes(bytes);
ctx.pc += 4;
}
```
xenia-rs interpreter body (frozen snapshot)
```rust
PpcOpcode::lvewx128 => {
let ea = ea_indexed(ctx, instr) & !0xF;
let mut bytes = [0u8; 16];
for i in 0..16 { bytes[i] = mem.read_u8(ea + i as u32); }
ctx.vr[instr.vd128()] = xenia_types::Vec128::from_bytes(bytes);
ctx.pc += 4;
}
```