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<!---======================= begin_copyright_notice ============================
Copyright (C) 2020-2021 Intel Corporation
SPDX-License-Identifier: MIT
============================= end_copyright_notice ==========================-->
## Opcode
3D_SAMPLE = 0x6d
## Format
### CONDITION
- Op.op=LOD, sample, sample_lz
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| 0x6d(3D_SAMPLE) | Op | Exec_size | Pred | Channels | Aoffimmi | Sampler |
| | Surface | Dst | NumParams | U | V | R |
| | Ai | | | | | |
### CONDITION
- Op.op=sample_b
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| 0x6d(3D_SAMPLE) | Op | Exec_size | Pred | Channels | Aoffimmi | Sampler |
| | Surface | Dst | NumParams | Bias\* | U | V |
| | R | Ai | | | | |
### CONDITION
- Op.op=sample_b_c
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| 0x6d(3D_SAMPLE) | Op | Exec_size | Pred | Channels | Aoffimmi | Sampler |
| | Surface | Dst | NumParams | Ref\* | Bias\* | U |
| | V | R | Ai | | | |
### CONDITION
- Op.op=sample_c, sample_c_lz
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| 0x6d(3D_SAMPLE) | Op | Exec_size | Pred | Channels | Aoffimmi | Sampler |
| | Surface | Dst | NumParams | Ref\* | U | V |
| | R | Ai | | | | |
### CONDITION
- Op.op=sample_d
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| 0x6d(3D_SAMPLE) | Op | Exec_size | Pred | Channels | Aoffimmi | Sampler |
| | Surface | Dst | NumParams | U | Dudx\* | Dudy\* |
| | V | Dvdx\* | Dvdy\* | R | Drdx\* | Drdy\* |
| | Ai | | | | | |
### CONDITION
- Op.op=sample_d_c
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| 0x6d(3D_SAMPLE) | Op | Exec_size | Pred | Channels | Aoffimmi | Sampler |
| | Surface | Dst | NumParams | Ref\* | U | Dudx\* |
| | Dudy\* | V | Dvdx\* | Dvdy\* | R | Drdx\* |
| | Drdy\* | Ai | | | | |
### CONDITION
- Op.op=sample_l
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| 0x6d(3D_SAMPLE) | Op | Exec_size | Pred | Channels | Aoffimmi | Sampler |
| | Surface | Dst | NumParams | Lod\* | U | V |
| | R | Ai | | | | |
### CONDITION
- Op.op=sample_l_c
| | | | | | | |
| --- | --- | --- | --- | --- | --- | --- |
| 0x6d(3D_SAMPLE) | Op | Exec_size | Pred | Channels | Aoffimmi | Sampler |
| | Surface | Dst | NumParams | Ref\* | Lod\* | U |
| | V | R | Ai | | | |
## Semantics
Sample a surface
## Description
Samples <surface> using the indicated sampler state <sampler>. LOD, bias, ref, and gradients are computed differently based on the sampler operation. Up to 4 channels of data is returned for each pixel in <dst>.
- **Op(ub):**
- Bit[4..0]: encodes the sampler operation
- 0b00000: sample
- 0b00001: sample_b
- 0b00010: sample_l
- 0b00011: sample_c
- 0b00100: sample_d
- 0b00101: sample_b_c
- 0b00110: sample_l_c
- 0b01001: LOD
- 0b10100: sample_d_c
- 0b11000: sample_lz
- 0b11001: sample_c_lz
- Bit[5]: pixel null mask enable. Specifies whether the writeback message will include an extra phase indicating the pixel null mask.
- {ICLLP+}Bit[6]: CPS LOD compensation enable. Only available for sample, sample_b, sample_bc, sample_c, and LOD.
- Bit[7]: non-uniform sampler state. true if the sampler field may be different for each thread
- **Exec_size(ub):** Execution size
- Bit[2..0]: size of the region for source and destination operands
- 0b011: 8 elements
- 0b100: 16 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)
- **Aoffimmi(scalar):** A UW representing the _aoffimmi modifier with the following format:
- Bit[3..0]: stores the R offset. Valid values are [-8-7]
- Bit[7..4]: stores the V offset. Valid values are [-8-7]
- Bit[11..8]: stores the U offset. Valid values are [-8-7]
- Bit[15..12]: reserved. Must be zero
- **Sampler(ub):** Index of the sampler variable
- **Surface(ub):** Index of the surface variable
- **Dst(raw_operand):** The result of the sample. Must have type HF,F,W,UW,D,UD
- **NumParams(ub):** number of additional parameters for this instruction. Valid values are [1-15]
- **Ref(raw_operand):** The first <exec_size> elements contain the reference value that is compared against the red channel of the sampled surface
- **Bias(raw_operand):** The first <exec_size> elements contain the LOD bias, with range of [-16.0, 16.0]
- **Lod(raw_operand):** The first <exec_size> elements contain the LOD
- **U(raw_operand):** The first <exec_size> elements contain the normalized x coordinates
- **Dudx(raw_operand):** The first <exec_size> elements contain the gradients of the u coordinate
- **Dudy(raw_operand):** The first <exec_size> elements contain the gradients of the u coordinate
- **V(raw_operand):** The first <exec_size> elements contain for
- 1D_array surfaces: unnormalized array index
- Other surface types: normalized y coordinate
- **Dvdx(raw_operand):** The first <exec_size> elements contain the gradients of the v coordinate
- **Dvdy(raw_operand):** The first <exec_size> elements contain the gradients of the v coordinate
- **R(raw_operand):** The first <exec_size> elements contain for
- 2D_array: the unnormalized array index.
- Other surface types: the normalized z coordinates
- **Drdx(raw_operand):** The first <exec_size> elements contain the gradients of the r coordinate
- **Drdy(raw_operand):** The first <exec_size> elements contain the gradients of the v coordinate
- **Ai(raw_operand):** The first <exec_size> elements contain the array index for a cube surface
#### Properties
## Text
```
[(<P>)] SAMPLE_3d[.pixel_null_mask][.cps][.divS][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <u> <v> <r> <ai>
[(<P>)] SAMPLE_B[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <bias> <u> <v> <r> <ai>
[(<P>)] SAMPLE_L[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <lod> <u> <v> <r> <ai>
[(<P>)] SAMPLE_C[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <ref> <u> <v> <r> <ai>
[(<P>)] SAMPLE_D[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <u> <dudx> <dudy> <v> <dvdx> <dvdy> <r> <drdx> <drdy> <ai>
[(<P>)] SAMPLE_B_C[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <ref> <bias> <u> <v> <r> <ai>
[(<P>)] SAMPLE_L_C[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <ref> <lod> <u> <v> <r> <ai>
[(<P>)] LOD[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <u> <v> <r> <ai>
[(<P>)] SAMPLE_D_C[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <ref> <u> <dudx> <dudy> <v> <dvdx> <dvdy> <r> <drdx> <drdy> <ai>
[(<P>)] SAMPLE_LZ[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <u> <v> <r> <ai>
[(<P>)] SAMPLE_C_LZ[.pixel_null_mask][.cps][.divS].<Channels> (Exec_size) <Aoffimmi> <Sampler> <Surface> <Dst> <ref> <u> <v> <r> <ai>
// instruction specific parameters may vary
```
## Notes
For each enabled channel <exec_size> elements are returned in RGBA order, with the disabled channels skipped in the results. Only the enabled pixels are returned in <dst>. Each channel's return data start in the next GRF; if <exec_size> * sizeof(dst_type) is smaller than the register size, the remaining portions of the register have undefined values.
For LOD operation: R channel contains the clamped LOD values while G channel contains the unclamped LOD values. B and A channels have undefined values and should be masked out.
For all operations, if <pixel_null_mask> is set, an additional GRF is returned after the sampler data, with <exec_size> bits in the first DWord containing the pixel null mask values. This field has the bit for all pixels set to 1 except those pixels in which a null page was source for at least one texel.
Extra parameters (after NumParams) for this instruction are required only for certain operations and surface types.
- **{pre-ICLLP}** All operands must have type F.
- **{ICLLP+}** All operands must have the same type, which can be either HF or F.
- It is permitted to skip the trailing parameters; the missing parameters will have the value of 0.
The table below summarizes the additional arguments for each of the sampler operations.
+-----------------+------------------------------------------------------------------------------------------------+
| Operation | Parameters |
| +--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample | u | v | r | ai | | | | | | | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample_b | bias | u | v | r | ai | | | | | | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample_l | lod | u | v | r | ai | | | | | | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample_c | ref | u | v | r | ai | | | | | | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample_d | u | dudx | dudy | v | dvdx | dvdy | r | drdx | drdy | ai | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample_b_c | ref | bias | u | v | r | ai | | | | | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample_l_c | ref | lod | u | v | r | ai | | | | | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| LOD | u | v | r | ai | | | | | | | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample_d_c | ref | u | dudx | dudy | v | dvdx | dvdy | r | drdx | drdy | ai |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample_lz | u | v | r | ai | | | | | | | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
| sample_c_lz | ref | u | v | r | ai | | | | | | |
+-----------------+--------+--------+--------+--------+--------+--------+--------+--------+--------+--------+------+
The table below describes the meanings of the u, v, r, ai parameters based on the surface type.
+----------------+-----------------------------+-----------------------------+-----------------------------+----------------------------+
| Surface Type | u | v | r | ai |
+----------------+-----------------------------+-----------------------------+-----------------------------+----------------------------+
| 1D/1D_ARRAY | normalized 'x' coordinate | unnormalized array index | ignored | ignored |
+----------------+-----------------------------+-----------------------------+-----------------------------+----------------------------+
| 2D/2D_ARRAY | normalized 'x' coordinate | normalized 'y' coordinate | unnormalized array index | ignored |
+----------------+-----------------------------+-----------------------------+-----------------------------+----------------------------+
| 3D | normalized 'x' coordinate | normalized 'y' coordinate | normalized 'z' coordinate | ignored |
+----------------+-----------------------------+-----------------------------+-----------------------------+----------------------------+
| CUBE | normalized 'x' coordinate | normalized 'y' coordinate | normalized 'z' coordinate | unnormalized array index |
+----------------+-----------------------------+-----------------------------+-----------------------------+----------------------------+
|
