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Copyright (C) 2020-2021 Intel Corporation

SPDX-License-Identifier: MIT

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## Opcode

  CALL = 0x33

## Format

| | | |
| --- | --- | --- |
| 0x33(CALL) | Exec_size | Pred | Label |


## Semantics




                    Calls the subroutine at <label>

## Description


    Calls the subroutine <label> based on the predicate value.

    * If <exec_size> is one:

      * Execution jumps to the subroutine if the predicate is true. The call mask will be initialized to all ones at subroutine entry. Scalar calls must be marked with {NoMask}.

    * If <exec_size> is greater than one:

      * The call is executed if any of the active channels are predicated. At subroutine entry, the call mask will be initialized to the set of active channels that are predicated.

- **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

- **Label(uw):** Index of the label variable for the subroutine. It must be a function label

#### Properties
- **Source Modifier:** false 


## Text
```
    

		[(<P>)] CALL (<exec_size>) <label>
```



## Notes



		Dynamic subroutine call through a variable is not supported.
