# Form `MDS` — MDS — Mask Double, Shift-by-register (rldcl/rldcr)

## Bit Layout

| Bits | Field | Meaning |
| --- | --- | --- |
| 0–5 | `OPCD` | primary opcode (30) |
| 6–10 | `RS` | source GPR |
| 11–15 | `RA` | destination GPR |
| 16–20 | `RB` | source B GPR |
| 21–26 | `mb/me` | 6-bit mask field (swapped halves) |
| 27–30 | `XO` | extended opcode |
| 31 | `Rc` | record-form flag |

## Instructions Using This Form

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| Mnemonic | Opcode | Group | Description |
| --- | --- | --- | --- |
| [`rldclx`](../alu/rldclx.md) | `0x78000010` | integer | Rotate Left Doubleword then Clear Left |
| [`rldcrx`](../alu/rldcrx.md) | `0x78000012` | integer | Rotate Left Doubleword then Clear Right |

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