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Copyright (C) 2020-2022 Intel Corporation

SPDX-License-Identifier: MIT

============================= end_copyright_notice ==========================-->

## Opcode

  LZD = 0x1f

## Format

| | | | | |
| --- | --- | --- | --- | --- |
| 0x1f(LZD) | Exec_size | Pred | Dst | Src0 |


## Semantics


```

                    for (i = 0; i < exec_size; ++i){
                      if (ChEn[i]) {
                        UD cnt = 0;
                        UD udScalar = src0[i];
                        while ((udScalar & (1<<31)) == 0 && cnt !=32){
                          cnt++;
                          udScalar = udScalar << 1;
                        }
                        dst.chan[n] = cnt;
                      }
                    }
```

## Description





```
    Performs component-wise leading zero detection (counting the number of leading zeros) of <src0> and stores the results in <dst>. If <src0> is zero, 32 is returned.
```


- **Exec_size(ub):** Execution size

  - Bit[2..0]: size of the region for source and destination operands

    - 0b000:  1 element (scalar)
    - 0b001:  2 elements
    - 0b010:  4 elements
    - 0b011:  8 elements
    - 0b100:  16 elements
    - 0b101:  32 elements
  - Bit[7..4]: execution mask (explicit control over the enabled channels)

    - 0b0000:  M1
    - 0b0001:  M2
    - 0b0010:  M3
    - 0b0011:  M4
    - 0b0100:  M5
    - 0b0101:  M6
    - 0b0110:  M7
    - 0b0111:  M8
    - 0b1000:  M1_NM
    - 0b1001:  M2_NM
    - 0b1010:  M3_NM
    - 0b1011:  M4_NM
    - 0b1100:  M5_NM
    - 0b1101:  M6_NM
    - 0b1110:  M7_NM
    - 0b1111:  M8_NM

- **Pred(uw):** Predication control


- **Dst(vec_operand):** The destination operand. Operand class: general,indirect


- **Src0(vec_operand):** The first source operand. Operand class: general,indirect,immediate


#### Properties
- **Supported Types:** UD
- **Saturation:** Yes
- **Source Modifier:** false




## Text
```
[(<P>)] LZD[.sat] (<exec_size>) <dst> <src0>
```

## Notes





    This should be mapped to the GEN LZD instruction.

