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<!---======================= begin_copyright_notice ============================
Copyright (C) 2020-2021 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ==========================-->
## Opcode
SCATTER4_TYPED = 0x4c
## Format
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| 0x4c(SCATTER4_TYPED) | Exec_size | Pred | Channels | Surface | U | V |
| | R | LOD | Src | | | |
## Semantics
UD ch_pos = 0;
for (c = 0; c < 4; ++c) {
if (ch_mask[c] == 1) {
for (i = 0; i < exec_size; ++i) {
if (ChEn[i]) {
UD ch_start = ch_pos * max(exec_size, GRF_SIZE / 4); // GRF_SIZE is the register size in bytes
*(&surface[u][v][r] + c) = src[ch_start+i]; //one pixel, with type conversion
}
}
ch_pos++;
}
}
## Description
Performs <exec_size>*<num_enabled_channels> dword scattered write into <surface>, using the values from <src>.
- **Exec_size(ub):** Execution size
- Bit[2..0]: size of the region for source and destination operands
- 0b011: 8 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
- **Channels(ub):**
- Bit[3..0]: determines the write masks for the RGBA channel, with R being bit 0 and A bit 3. At least one channel must be enabled (i.e., "0000" is not allowed)
- **Surface(ub):** Index of the surface variable. It must be a 1D, 2D, or 3D surface.
- T0 (SLM): no
- T5 (stateless): no
- **U(raw_operand):** The first exec_size elements contain the U offset. Must have type UD
- **V(raw_operand):** The first exec_size elements contain the V offset. Must have type UD
- **R(raw_operand):** The first exec_size elements contain the R offset. Must have type UD
- **LOD(raw_operand):** The first exec_size elements contain the LOD. Must have type UD
- **Src(raw_operand):** The values to be written. For each enabled channel in RGBA order, exec_size elements will be written to the surface subject to predication. The next enabled channel will get its data from the next register. Must have type UD,D,F
#### Properties
- **Out-of-bound Access:** On write: data is dropped.
## Text
```
[(<P>)] SCATTER4_TYPED.<channels> (<exec_size>) <surface> <u> <v> <r> <lod> <src>
//<channels> is one of R, G, B, A, RG, RB, RA, RGB, RGBA, GB, GA, GBA, BA
```
## Notes
.. table:: Type conversion from register to surface is performed based on the following rules:
:align: center
+---------------------+------------------------+--------------------------------------------------------------------------------------------------+
| Src Data Type | Surface Format Type | Write Conversion |
+---------------------+------------------------+--------------------------------------------------------------------------------------------------+
| F | FLOAT |IEEE float conversion. Round to even and denormalize if destination is narrower. |
+---------------------+------------------------+--------------------------------------------------------------------------------------------------+
| F | SNORM, UNORM |Convert IEEE float to fixed point. Round to even and clamp to min/max if destination is narrower. |
+---------------------+------------------------+--------------------------------------------------------------------------------------------------+
| D | SINT |Clamp to min/max if destination is narrower. |
+---------------------+------------------------+--------------------------------------------------------------------------------------------------+
| UD | UINT |Clamp to min/max if destination is narrower. |
+---------------------+------------------------+--------------------------------------------------------------------------------------------------+
The behavior is undefined if more than one channel writes to the same address.
If an offset operand is not applicable for the surface accessed (e.g., V and R for 1D surfaces), it should be set to V0 (the null variable).
|
