4 TGSI, Tungsten Graphics Shader Infrastructure, is an intermediate language
5 for describing shaders. Since Gallium is inherently shaderful, shaders are
6 an important part of the API. TGSI is the only intermediate representation
12 All TGSI instructions, known as *opcodes*, operate on arbitrary-precision
13 floating-point four-component vectors. An opcode may have up to one
14 destination register, known as *dst*, and between zero and three source
15 registers, called *src0* through *src2*, or simply *src* if there is only
18 Some instructions, like :opcode:`I2F`, permit re-interpretation of vector
19 components as integers. Other instructions permit using registers as
20 two-component vectors with double precision; see :ref:`Double Opcodes`.
22 When an instruction has a scalar result, the result is usually copied into
23 each of the components of *dst*. When this happens, the result is said to be
24 *replicated* to *dst*. :opcode:`RCP` is one such instruction.
30 ^^^^^^^^^^^^^^^^^^^^^^^^^
32 These opcodes are guaranteed to be available regardless of the driver being
35 .. opcode:: ARL - Address Register Load
39 dst.x = \lfloor src.x\rfloor
41 dst.y = \lfloor src.y\rfloor
43 dst.z = \lfloor src.z\rfloor
45 dst.w = \lfloor src.w\rfloor
48 .. opcode:: MOV - Move
61 .. opcode:: LIT - Light Coefficients
69 dst.z = (src.x > 0) ? max(src.y, 0)^{clamp(src.w, -128, 128))} : 0
74 .. opcode:: RCP - Reciprocal
76 This instruction replicates its result.
83 .. opcode:: RSQ - Reciprocal Square Root
85 This instruction replicates its result.
89 dst = \frac{1}{\sqrt{|src.x|}}
92 .. opcode:: EXP - Approximate Exponential Base 2
96 dst.x = 2^{\lfloor src.x\rfloor}
98 dst.y = src.x - \lfloor src.x\rfloor
105 .. opcode:: LOG - Approximate Logarithm Base 2
109 dst.x = \lfloor\log_2{|src.x|}\rfloor
111 dst.y = \frac{|src.x|}{2^{\lfloor\log_2{|src.x|}\rfloor}}
113 dst.z = \log_2{|src.x|}
118 .. opcode:: MUL - Multiply
122 dst.x = src0.x \times src1.x
124 dst.y = src0.y \times src1.y
126 dst.z = src0.z \times src1.z
128 dst.w = src0.w \times src1.w
131 .. opcode:: ADD - Add
135 dst.x = src0.x + src1.x
137 dst.y = src0.y + src1.y
139 dst.z = src0.z + src1.z
141 dst.w = src0.w + src1.w
144 .. opcode:: DP3 - 3-component Dot Product
146 This instruction replicates its result.
150 dst = src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z
153 .. opcode:: DP4 - 4-component Dot Product
155 This instruction replicates its result.
159 dst = src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z + src0.w \times src1.w
162 .. opcode:: DST - Distance Vector
168 dst.y = src0.y \times src1.y
175 .. opcode:: MIN - Minimum
179 dst.x = min(src0.x, src1.x)
181 dst.y = min(src0.y, src1.y)
183 dst.z = min(src0.z, src1.z)
185 dst.w = min(src0.w, src1.w)
188 .. opcode:: MAX - Maximum
192 dst.x = max(src0.x, src1.x)
194 dst.y = max(src0.y, src1.y)
196 dst.z = max(src0.z, src1.z)
198 dst.w = max(src0.w, src1.w)
201 .. opcode:: SLT - Set On Less Than
205 dst.x = (src0.x < src1.x) ? 1 : 0
207 dst.y = (src0.y < src1.y) ? 1 : 0
209 dst.z = (src0.z < src1.z) ? 1 : 0
211 dst.w = (src0.w < src1.w) ? 1 : 0
214 .. opcode:: SGE - Set On Greater Equal Than
218 dst.x = (src0.x >= src1.x) ? 1 : 0
220 dst.y = (src0.y >= src1.y) ? 1 : 0
222 dst.z = (src0.z >= src1.z) ? 1 : 0
224 dst.w = (src0.w >= src1.w) ? 1 : 0
227 .. opcode:: MAD - Multiply And Add
231 dst.x = src0.x \times src1.x + src2.x
233 dst.y = src0.y \times src1.y + src2.y
235 dst.z = src0.z \times src1.z + src2.z
237 dst.w = src0.w \times src1.w + src2.w
240 .. opcode:: SUB - Subtract
244 dst.x = src0.x - src1.x
246 dst.y = src0.y - src1.y
248 dst.z = src0.z - src1.z
250 dst.w = src0.w - src1.w
253 .. opcode:: LRP - Linear Interpolate
257 dst.x = src0.x \times src1.x + (1 - src0.x) \times src2.x
259 dst.y = src0.y \times src1.y + (1 - src0.y) \times src2.y
261 dst.z = src0.z \times src1.z + (1 - src0.z) \times src2.z
263 dst.w = src0.w \times src1.w + (1 - src0.w) \times src2.w
266 .. opcode:: CND - Condition
270 dst.x = (src2.x > 0.5) ? src0.x : src1.x
272 dst.y = (src2.y > 0.5) ? src0.y : src1.y
274 dst.z = (src2.z > 0.5) ? src0.z : src1.z
276 dst.w = (src2.w > 0.5) ? src0.w : src1.w
279 .. opcode:: DP2A - 2-component Dot Product And Add
283 dst.x = src0.x \times src1.x + src0.y \times src1.y + src2.x
285 dst.y = src0.x \times src1.x + src0.y \times src1.y + src2.x
287 dst.z = src0.x \times src1.x + src0.y \times src1.y + src2.x
289 dst.w = src0.x \times src1.x + src0.y \times src1.y + src2.x
292 .. opcode:: FRC - Fraction
296 dst.x = src.x - \lfloor src.x\rfloor
298 dst.y = src.y - \lfloor src.y\rfloor
300 dst.z = src.z - \lfloor src.z\rfloor
302 dst.w = src.w - \lfloor src.w\rfloor
305 .. opcode:: CLAMP - Clamp
309 dst.x = clamp(src0.x, src1.x, src2.x)
311 dst.y = clamp(src0.y, src1.y, src2.y)
313 dst.z = clamp(src0.z, src1.z, src2.z)
315 dst.w = clamp(src0.w, src1.w, src2.w)
318 .. opcode:: FLR - Floor
320 This is identical to :opcode:`ARL`.
324 dst.x = \lfloor src.x\rfloor
326 dst.y = \lfloor src.y\rfloor
328 dst.z = \lfloor src.z\rfloor
330 dst.w = \lfloor src.w\rfloor
333 .. opcode:: ROUND - Round
346 .. opcode:: EX2 - Exponential Base 2
348 This instruction replicates its result.
355 .. opcode:: LG2 - Logarithm Base 2
357 This instruction replicates its result.
364 .. opcode:: POW - Power
366 This instruction replicates its result.
370 dst = src0.x^{src1.x}
372 .. opcode:: XPD - Cross Product
376 dst.x = src0.y \times src1.z - src1.y \times src0.z
378 dst.y = src0.z \times src1.x - src1.z \times src0.x
380 dst.z = src0.x \times src1.y - src1.x \times src0.y
385 .. opcode:: ABS - Absolute
398 .. opcode:: RCC - Reciprocal Clamped
400 This instruction replicates its result.
402 XXX cleanup on aisle three
406 dst = (1 / src.x) > 0 ? clamp(1 / src.x, 5.42101e-020, 1.884467e+019) : clamp(1 / src.x, -1.884467e+019, -5.42101e-020)
409 .. opcode:: DPH - Homogeneous Dot Product
411 This instruction replicates its result.
415 dst = src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z + src1.w
418 .. opcode:: COS - Cosine
420 This instruction replicates its result.
427 .. opcode:: DDX - Derivative Relative To X
431 dst.x = partialx(src.x)
433 dst.y = partialx(src.y)
435 dst.z = partialx(src.z)
437 dst.w = partialx(src.w)
440 .. opcode:: DDY - Derivative Relative To Y
444 dst.x = partialy(src.x)
446 dst.y = partialy(src.y)
448 dst.z = partialy(src.z)
450 dst.w = partialy(src.w)
453 .. opcode:: KILP - Predicated Discard
458 .. opcode:: PK2H - Pack Two 16-bit Floats
463 .. opcode:: PK2US - Pack Two Unsigned 16-bit Scalars
468 .. opcode:: PK4B - Pack Four Signed 8-bit Scalars
473 .. opcode:: PK4UB - Pack Four Unsigned 8-bit Scalars
478 .. opcode:: RFL - Reflection Vector
482 dst.x = 2 \times (src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z) / (src0.x \times src0.x + src0.y \times src0.y + src0.z \times src0.z) \times src0.x - src1.x
484 dst.y = 2 \times (src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z) / (src0.x \times src0.x + src0.y \times src0.y + src0.z \times src0.z) \times src0.y - src1.y
486 dst.z = 2 \times (src0.x \times src1.x + src0.y \times src1.y + src0.z \times src1.z) / (src0.x \times src0.x + src0.y \times src0.y + src0.z \times src0.z) \times src0.z - src1.z
492 Considered for removal.
495 .. opcode:: SEQ - Set On Equal
499 dst.x = (src0.x == src1.x) ? 1 : 0
501 dst.y = (src0.y == src1.y) ? 1 : 0
503 dst.z = (src0.z == src1.z) ? 1 : 0
505 dst.w = (src0.w == src1.w) ? 1 : 0
508 .. opcode:: SFL - Set On False
510 This instruction replicates its result.
518 Considered for removal.
521 .. opcode:: SGT - Set On Greater Than
525 dst.x = (src0.x > src1.x) ? 1 : 0
527 dst.y = (src0.y > src1.y) ? 1 : 0
529 dst.z = (src0.z > src1.z) ? 1 : 0
531 dst.w = (src0.w > src1.w) ? 1 : 0
534 .. opcode:: SIN - Sine
536 This instruction replicates its result.
543 .. opcode:: SLE - Set On Less Equal Than
547 dst.x = (src0.x <= src1.x) ? 1 : 0
549 dst.y = (src0.y <= src1.y) ? 1 : 0
551 dst.z = (src0.z <= src1.z) ? 1 : 0
553 dst.w = (src0.w <= src1.w) ? 1 : 0
556 .. opcode:: SNE - Set On Not Equal
560 dst.x = (src0.x != src1.x) ? 1 : 0
562 dst.y = (src0.y != src1.y) ? 1 : 0
564 dst.z = (src0.z != src1.z) ? 1 : 0
566 dst.w = (src0.w != src1.w) ? 1 : 0
569 .. opcode:: STR - Set On True
571 This instruction replicates its result.
578 .. opcode:: TEX - Texture Lookup
586 dst = texture_sample(unit, coord, bias)
588 for array textures src0.y contains the slice for 1D,
589 and src0.z contain the slice for 2D.
590 for shadow textures with no arrays, src0.z contains
592 for shadow textures with arrays, src0.z contains
593 the reference value for 1D arrays, and src0.w contains
594 the reference value for 2D arrays.
595 There is no way to pass a bias in the .w value for
596 shadow arrays, and GLSL doesn't allow this.
597 GLSL does allow cube shadows maps to take a bias value,
598 and we have to determine how this will look in TGSI.
600 .. opcode:: TXD - Texture Lookup with Derivatives
612 dst = texture_sample_deriv(unit, coord, bias, ddx, ddy)
615 .. opcode:: TXP - Projective Texture Lookup
619 coord.x = src0.x / src.w
621 coord.y = src0.y / src.w
623 coord.z = src0.z / src.w
629 dst = texture_sample(unit, coord, bias)
632 .. opcode:: UP2H - Unpack Two 16-Bit Floats
638 Considered for removal.
640 .. opcode:: UP2US - Unpack Two Unsigned 16-Bit Scalars
646 Considered for removal.
648 .. opcode:: UP4B - Unpack Four Signed 8-Bit Values
654 Considered for removal.
656 .. opcode:: UP4UB - Unpack Four Unsigned 8-Bit Scalars
662 Considered for removal.
664 .. opcode:: X2D - 2D Coordinate Transformation
668 dst.x = src0.x + src1.x \times src2.x + src1.y \times src2.y
670 dst.y = src0.y + src1.x \times src2.z + src1.y \times src2.w
672 dst.z = src0.x + src1.x \times src2.x + src1.y \times src2.y
674 dst.w = src0.y + src1.x \times src2.z + src1.y \times src2.w
678 Considered for removal.
681 .. opcode:: ARA - Address Register Add
687 Considered for removal.
689 .. opcode:: ARR - Address Register Load With Round
702 .. opcode:: BRA - Branch
708 Considered for removal.
710 .. opcode:: CAL - Subroutine Call
716 .. opcode:: RET - Subroutine Call Return
721 .. opcode:: SSG - Set Sign
725 dst.x = (src.x > 0) ? 1 : (src.x < 0) ? -1 : 0
727 dst.y = (src.y > 0) ? 1 : (src.y < 0) ? -1 : 0
729 dst.z = (src.z > 0) ? 1 : (src.z < 0) ? -1 : 0
731 dst.w = (src.w > 0) ? 1 : (src.w < 0) ? -1 : 0
734 .. opcode:: CMP - Compare
738 dst.x = (src0.x < 0) ? src1.x : src2.x
740 dst.y = (src0.y < 0) ? src1.y : src2.y
742 dst.z = (src0.z < 0) ? src1.z : src2.z
744 dst.w = (src0.w < 0) ? src1.w : src2.w
747 .. opcode:: KIL - Conditional Discard
751 if (src.x < 0 || src.y < 0 || src.z < 0 || src.w < 0)
756 .. opcode:: SCS - Sine Cosine
769 .. opcode:: TXB - Texture Lookup With Bias
783 dst = texture_sample(unit, coord, bias)
786 .. opcode:: NRM - 3-component Vector Normalise
790 dst.x = src.x / (src.x \times src.x + src.y \times src.y + src.z \times src.z)
792 dst.y = src.y / (src.x \times src.x + src.y \times src.y + src.z \times src.z)
794 dst.z = src.z / (src.x \times src.x + src.y \times src.y + src.z \times src.z)
799 .. opcode:: DIV - Divide
803 dst.x = \frac{src0.x}{src1.x}
805 dst.y = \frac{src0.y}{src1.y}
807 dst.z = \frac{src0.z}{src1.z}
809 dst.w = \frac{src0.w}{src1.w}
812 .. opcode:: DP2 - 2-component Dot Product
814 This instruction replicates its result.
818 dst = src0.x \times src1.x + src0.y \times src1.y
821 .. opcode:: TXL - Texture Lookup With explicit LOD
835 dst = texture_sample(unit, coord, lod)
838 .. opcode:: BRK - Break
848 .. opcode:: ELSE - Else
853 .. opcode:: ENDIF - End If
858 .. opcode:: PUSHA - Push Address Register On Stack
867 Considered for cleanup.
871 Considered for removal.
873 .. opcode:: POPA - Pop Address Register From Stack
882 Considered for cleanup.
886 Considered for removal.
890 ^^^^^^^^^^^^^^^^^^^^^^^^
892 These opcodes are primarily provided for special-use computational shaders.
893 Support for these opcodes indicated by a special pipe capability bit (TBD).
895 XXX so let's discuss it, yeah?
897 .. opcode:: CEIL - Ceiling
901 dst.x = \lceil src.x\rceil
903 dst.y = \lceil src.y\rceil
905 dst.z = \lceil src.z\rceil
907 dst.w = \lceil src.w\rceil
910 .. opcode:: I2F - Integer To Float
914 dst.x = (float) src.x
916 dst.y = (float) src.y
918 dst.z = (float) src.z
920 dst.w = (float) src.w
923 .. opcode:: NOT - Bitwise Not
936 .. opcode:: TRUNC - Truncate
949 .. opcode:: SHL - Shift Left
953 dst.x = src0.x << src1.x
955 dst.y = src0.y << src1.x
957 dst.z = src0.z << src1.x
959 dst.w = src0.w << src1.x
962 .. opcode:: SHR - Shift Right
966 dst.x = src0.x >> src1.x
968 dst.y = src0.y >> src1.x
970 dst.z = src0.z >> src1.x
972 dst.w = src0.w >> src1.x
975 .. opcode:: AND - Bitwise And
979 dst.x = src0.x & src1.x
981 dst.y = src0.y & src1.y
983 dst.z = src0.z & src1.z
985 dst.w = src0.w & src1.w
988 .. opcode:: OR - Bitwise Or
992 dst.x = src0.x | src1.x
994 dst.y = src0.y | src1.y
996 dst.z = src0.z | src1.z
998 dst.w = src0.w | src1.w
1001 .. opcode:: MOD - Modulus
1005 dst.x = src0.x \bmod src1.x
1007 dst.y = src0.y \bmod src1.y
1009 dst.z = src0.z \bmod src1.z
1011 dst.w = src0.w \bmod src1.w
1014 .. opcode:: XOR - Bitwise Xor
1018 dst.x = src0.x \oplus src1.x
1020 dst.y = src0.y \oplus src1.y
1022 dst.z = src0.z \oplus src1.z
1024 dst.w = src0.w \oplus src1.w
1027 .. opcode:: UCMP - Integer Conditional Move
1031 dst.x = src0.x ? src1.x : src2.x
1033 dst.y = src0.y ? src1.y : src2.y
1035 dst.z = src0.z ? src1.z : src2.z
1037 dst.w = src0.w ? src1.w : src2.w
1040 .. opcode:: UARL - Integer Address Register Load
1042 Moves the contents of the source register, assumed to be an integer, into the
1043 destination register, which is assumed to be an address (ADDR) register.
1046 .. opcode:: IABS - Integer Absolute Value
1059 .. opcode:: SAD - Sum Of Absolute Differences
1063 dst.x = |src0.x - src1.x| + src2.x
1065 dst.y = |src0.y - src1.y| + src2.y
1067 dst.z = |src0.z - src1.z| + src2.z
1069 dst.w = |src0.w - src1.w| + src2.w
1072 .. opcode:: TXF - Texel Fetch (as per NV_gpu_shader4), extract a single texel
1073 from a specified texture image. The source sampler may
1074 not be a CUBE or SHADOW.
1075 src 0 is a four-component signed integer vector used to
1076 identify the single texel accessed. 3 components + level.
1077 src 1 is a 3 component constant signed integer vector,
1078 with each component only have a range of
1079 -8..+8 (hw only seems to deal with this range, interface
1080 allows for up to unsigned int).
1081 TXF(uint_vec coord, int_vec offset).
1084 .. opcode:: TXQ - Texture Size Query (as per NV_gpu_program4)
1085 retrieve the dimensions of the texture
1086 depending on the target. For 1D (width), 2D/RECT/CUBE
1087 (width, height), 3D (width, height, depth),
1088 1D array (width, layers), 2D array (width, height, layers)
1094 dst.x = texture_width(unit, lod)
1096 dst.y = texture_height(unit, lod)
1098 dst.z = texture_depth(unit, lod)
1101 .. opcode:: CONT - Continue
1107 Support for CONT is determined by a special capability bit,
1108 ``TGSI_CONT_SUPPORTED``. See :ref:`Screen` for more information.
1112 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1114 These opcodes are only supported in geometry shaders; they have no meaning
1115 in any other type of shader.
1117 .. opcode:: EMIT - Emit
1122 .. opcode:: ENDPRIM - End Primitive
1130 These opcodes are part of :term:`GLSL`'s opcode set. Support for these
1131 opcodes is determined by a special capability bit, ``GLSL``.
1133 .. opcode:: BGNLOOP - Begin a Loop
1138 .. opcode:: BGNSUB - Begin Subroutine
1143 .. opcode:: ENDLOOP - End a Loop
1148 .. opcode:: ENDSUB - End Subroutine
1153 .. opcode:: NOP - No Operation
1158 .. opcode:: NRM4 - 4-component Vector Normalise
1160 This instruction replicates its result.
1164 dst = \frac{src.x}{src.x \times src.x + src.y \times src.y + src.z \times src.z + src.w \times src.w}
1172 .. opcode:: CALLNZ - Subroutine Call If Not Zero
1177 .. opcode:: IFC - If
1182 .. opcode:: BREAKC - Break Conditional
1191 The double-precision opcodes reinterpret four-component vectors into
1192 two-component vectors with doubled precision in each component.
1194 Support for these opcodes is XXX undecided. :T
1196 .. opcode:: DADD - Add
1200 dst.xy = src0.xy + src1.xy
1202 dst.zw = src0.zw + src1.zw
1205 .. opcode:: DDIV - Divide
1209 dst.xy = src0.xy / src1.xy
1211 dst.zw = src0.zw / src1.zw
1213 .. opcode:: DSEQ - Set on Equal
1217 dst.xy = src0.xy == src1.xy ? 1.0F : 0.0F
1219 dst.zw = src0.zw == src1.zw ? 1.0F : 0.0F
1221 .. opcode:: DSLT - Set on Less than
1225 dst.xy = src0.xy < src1.xy ? 1.0F : 0.0F
1227 dst.zw = src0.zw < src1.zw ? 1.0F : 0.0F
1229 .. opcode:: DFRAC - Fraction
1233 dst.xy = src.xy - \lfloor src.xy\rfloor
1235 dst.zw = src.zw - \lfloor src.zw\rfloor
1238 .. opcode:: DFRACEXP - Convert Number to Fractional and Integral Components
1240 Like the ``frexp()`` routine in many math libraries, this opcode stores the
1241 exponent of its source to ``dst0``, and the significand to ``dst1``, such that
1242 :math:`dst1 \times 2^{dst0} = src` .
1246 dst0.xy = exp(src.xy)
1248 dst1.xy = frac(src.xy)
1250 dst0.zw = exp(src.zw)
1252 dst1.zw = frac(src.zw)
1254 .. opcode:: DLDEXP - Multiply Number by Integral Power of 2
1256 This opcode is the inverse of :opcode:`DFRACEXP`.
1260 dst.xy = src0.xy \times 2^{src1.xy}
1262 dst.zw = src0.zw \times 2^{src1.zw}
1264 .. opcode:: DMIN - Minimum
1268 dst.xy = min(src0.xy, src1.xy)
1270 dst.zw = min(src0.zw, src1.zw)
1272 .. opcode:: DMAX - Maximum
1276 dst.xy = max(src0.xy, src1.xy)
1278 dst.zw = max(src0.zw, src1.zw)
1280 .. opcode:: DMUL - Multiply
1284 dst.xy = src0.xy \times src1.xy
1286 dst.zw = src0.zw \times src1.zw
1289 .. opcode:: DMAD - Multiply And Add
1293 dst.xy = src0.xy \times src1.xy + src2.xy
1295 dst.zw = src0.zw \times src1.zw + src2.zw
1298 .. opcode:: DRCP - Reciprocal
1302 dst.xy = \frac{1}{src.xy}
1304 dst.zw = \frac{1}{src.zw}
1306 .. opcode:: DSQRT - Square Root
1310 dst.xy = \sqrt{src.xy}
1312 dst.zw = \sqrt{src.zw}
1315 .. _samplingopcodes:
1317 Resource Sampling Opcodes
1318 ^^^^^^^^^^^^^^^^^^^^^^^^^
1320 Those opcodes follow very closely semantics of the respective Direct3D
1321 instructions. If in doubt double check Direct3D documentation.
1323 .. opcode:: SAMPLE - Using provided address, sample data from the
1324 specified texture using the filtering mode identified
1325 by the gven sampler. The source data may come from
1326 any resource type other than buffers.
1327 SAMPLE dst, address, sampler_view, sampler
1329 SAMPLE TEMP[0], TEMP[1], SVIEW[0], SAMP[0]
1331 .. opcode:: SAMPLE_I - Simplified alternative to the SAMPLE instruction.
1332 Using the provided integer address, SAMPLE_I fetches data
1333 from the specified sampler view without any filtering.
1334 The source data may come from any resource type other
1336 SAMPLE_I dst, address, sampler_view
1338 SAMPLE_I TEMP[0], TEMP[1], SVIEW[0]
1339 The 'address' is specified as unsigned integers. If the
1340 'address' is out of range [0...(# texels - 1)] the
1341 result of the fetch is always 0 in all components.
1342 As such the instruction doesn't honor address wrap
1343 modes, in cases where that behavior is desirable
1344 'SAMPLE' instruction should be used.
1345 address.w always provides an unsigned integer mipmap
1346 level. If the value is out of the range then the
1347 instruction always returns 0 in all components.
1348 address.yz are ignored for buffers and 1d textures.
1349 address.z is ignored for 1d texture arrays and 2d
1351 For 1D texture arrays address.y provides the array
1352 index (also as unsigned integer). If the value is
1353 out of the range of available array indices
1354 [0... (array size - 1)] then the opcode always returns
1355 0 in all components.
1356 For 2D texture arrays address.z provides the array
1357 index, otherwise it exhibits the same behavior as in
1358 the case for 1D texture arrays.
1359 The exact semantics of the source address are presented
1361 resource type X Y Z W
1362 ------------- ------------------------
1363 PIPE_BUFFER x ignored
1364 PIPE_TEXTURE_1D x mpl
1365 PIPE_TEXTURE_2D x y mpl
1366 PIPE_TEXTURE_3D x y z mpl
1367 PIPE_TEXTURE_RECT x y mpl
1368 PIPE_TEXTURE_CUBE not allowed as source
1369 PIPE_TEXTURE_1D_ARRAY x idx mpl
1370 PIPE_TEXTURE_2D_ARRAY x y idx mpl
1372 Where 'mpl' is a mipmap level and 'idx' is the
1375 .. opcode:: SAMPLE_I_MS - Just like SAMPLE_I but allows fetch data from
1376 multi-sampled surfaces.
1378 .. opcode:: SAMPLE_B - Just like the SAMPLE instruction with the
1379 exception that an additiona bias is applied to the
1380 level of detail computed as part of the instruction
1382 SAMPLE_B dst, address, sampler_view, sampler, lod_bias
1384 SAMPLE_B TEMP[0], TEMP[1], SVIEW[0], SAMP[0], TEMP[2].x
1386 .. opcode:: SAMPLE_C - Similar to the SAMPLE instruction but it
1387 performs a comparison filter. The operands to SAMPLE_C
1388 are identical to SAMPLE, except that tere is an additional
1389 float32 operand, reference value, which must be a register
1390 with single-component, or a scalar literal.
1391 SAMPLE_C makes the hardware use the current samplers
1392 compare_func (in pipe_sampler_state) to compare
1393 reference value against the red component value for the
1394 surce resource at each texel that the currently configured
1395 texture filter covers based on the provided coordinates.
1396 SAMPLE_C dst, address, sampler_view.r, sampler, ref_value
1398 SAMPLE_C TEMP[0], TEMP[1], SVIEW[0].r, SAMP[0], TEMP[2].x
1400 .. opcode:: SAMPLE_C_LZ - Same as SAMPLE_C, but LOD is 0 and derivatives
1401 are ignored. The LZ stands for level-zero.
1402 SAMPLE_C_LZ dst, address, sampler_view.r, sampler, ref_value
1404 SAMPLE_C_LZ TEMP[0], TEMP[1], SVIEW[0].r, SAMP[0], TEMP[2].x
1407 .. opcode:: SAMPLE_D - SAMPLE_D is identical to the SAMPLE opcode except
1408 that the derivatives for the source address in the x
1409 direction and the y direction are provided by extra
1411 SAMPLE_D dst, address, sampler_view, sampler, der_x, der_y
1413 SAMPLE_D TEMP[0], TEMP[1], SVIEW[0], SAMP[0], TEMP[2], TEMP[3]
1415 .. opcode:: SAMPLE_L - SAMPLE_L is identical to the SAMPLE opcode except
1416 that the LOD is provided directly as a scalar value,
1417 representing no anisotropy. Source addresses A channel
1419 SAMPLE_L dst, address, sampler_view, sampler
1421 SAMPLE_L TEMP[0], TEMP[1], SVIEW[0], SAMP[0]
1423 .. opcode:: GATHER4 - Gathers the four texels to be used in a bi-linear
1424 filtering operation and packs them into a single register.
1425 Only works with 2D, 2D array, cubemaps, and cubemaps arrays.
1426 For 2D textures, only the addressing modes of the sampler and
1427 the top level of any mip pyramid are used. Set W to zero.
1428 It behaves like the SAMPLE instruction, but a filtered
1429 sample is not generated. The four samples that contribute
1430 to filtering are placed into xyzw in counter-clockwise order,
1431 starting with the (u,v) texture coordinate delta at the
1432 following locations (-, +), (+, +), (+, -), (-, -), where
1433 the magnitude of the deltas are half a texel.
1436 .. opcode:: SVIEWINFO - query the dimensions of a given sampler view.
1437 dst receives width, height, depth or array size and
1438 number of mipmap levels. The dst can have a writemask
1439 which will specify what info is the caller interested
1441 SVIEWINFO dst, src_mip_level, sampler_view
1443 SVIEWINFO TEMP[0], TEMP[1].x, SVIEW[0]
1444 src_mip_level is an unsigned integer scalar. If it's
1445 out of range then returns 0 for width, height and
1446 depth/array size but the total number of mipmap is
1447 still returned correctly for the given sampler view.
1448 The returned width, height and depth values are for
1449 the mipmap level selected by the src_mip_level and
1450 are in the number of texels.
1451 For 1d texture array width is in dst.x, array size
1452 is in dst.y and dst.zw are always 0.
1454 .. opcode:: SAMPLE_POS - query the position of a given sample.
1455 dst receives float4 (x, y, 0, 0) indicated where the
1456 sample is located. If the resource is not a multi-sample
1457 resource and not a render target, the result is 0.
1459 .. opcode:: SAMPLE_INFO - dst receives number of samples in x.
1460 If the resource is not a multi-sample resource and
1461 not a render target, the result is 0.
1464 .. _resourceopcodes:
1466 Resource Access Opcodes
1467 ^^^^^^^^^^^^^^^^^^^^^^^
1469 .. opcode:: LOAD - Fetch data from a shader resource
1471 Syntax: ``LOAD dst, resource, address``
1473 Example: ``LOAD TEMP[0], RES[0], TEMP[1]``
1475 Using the provided integer address, LOAD fetches data
1476 from the specified buffer or texture without any
1479 The 'address' is specified as a vector of unsigned
1480 integers. If the 'address' is out of range the result
1483 Only the first mipmap level of a resource can be read
1484 from using this instruction.
1486 For 1D or 2D texture arrays, the array index is
1487 provided as an unsigned integer in address.y or
1488 address.z, respectively. address.yz are ignored for
1489 buffers and 1D textures. address.z is ignored for 1D
1490 texture arrays and 2D textures. address.w is always
1494 Explanation of symbols used
1495 ------------------------------
1502 :math:`|x|` Absolute value of `x`.
1504 :math:`\lceil x \rceil` Ceiling of `x`.
1506 clamp(x,y,z) Clamp x between y and z.
1507 (x < y) ? y : (x > z) ? z : x
1509 :math:`\lfloor x\rfloor` Floor of `x`.
1511 :math:`\log_2{x}` Logarithm of `x`, base 2.
1513 max(x,y) Maximum of x and y.
1516 min(x,y) Minimum of x and y.
1519 partialx(x) Derivative of x relative to fragment's X.
1521 partialy(x) Derivative of x relative to fragment's Y.
1523 pop() Pop from stack.
1525 :math:`x^y` `x` to the power `y`.
1527 push(x) Push x on stack.
1531 trunc(x) Truncate x, i.e. drop the fraction bits.
1538 discard Discard fragment.
1542 target Label of target instruction.
1553 Declares a register that is will be referenced as an operand in Instruction
1556 File field contains register file that is being declared and is one
1559 UsageMask field specifies which of the register components can be accessed
1560 and is one of TGSI_WRITEMASK.
1562 Interpolate field is only valid for fragment shader INPUT register files.
1563 It specifes the way input is being interpolated by the rasteriser and is one
1564 of TGSI_INTERPOLATE.
1566 If Dimension flag is set to 1, a Declaration Dimension token follows.
1568 If Semantic flag is set to 1, a Declaration Semantic token follows.
1570 CylindricalWrap bitfield is only valid for fragment shader INPUT register
1571 files. It specifies which register components should be subject to cylindrical
1572 wrapping when interpolating by the rasteriser. If TGSI_CYLINDRICAL_WRAP_X
1573 is set to 1, the X component should be interpolated according to cylindrical
1576 If file is TGSI_FILE_RESOURCE, a Declaration Resource token follows.
1579 Declaration Semantic
1580 ^^^^^^^^^^^^^^^^^^^^^^^^
1582 Vertex and fragment shader input and output registers may be labeled
1583 with semantic information consisting of a name and index.
1585 Follows Declaration token if Semantic bit is set.
1587 Since its purpose is to link a shader with other stages of the pipeline,
1588 it is valid to follow only those Declaration tokens that declare a register
1589 either in INPUT or OUTPUT file.
1591 SemanticName field contains the semantic name of the register being declared.
1592 There is no default value.
1594 SemanticIndex is an optional subscript that can be used to distinguish
1595 different register declarations with the same semantic name. The default value
1598 The meanings of the individual semantic names are explained in the following
1601 TGSI_SEMANTIC_POSITION
1602 """"""""""""""""""""""
1604 For vertex shaders, TGSI_SEMANTIC_POSITION indicates the vertex shader
1605 output register which contains the homogeneous vertex position in the clip
1606 space coordinate system. After clipping, the X, Y and Z components of the
1607 vertex will be divided by the W value to get normalized device coordinates.
1609 For fragment shaders, TGSI_SEMANTIC_POSITION is used to indicate that
1610 fragment shader input contains the fragment's window position. The X
1611 component starts at zero and always increases from left to right.
1612 The Y component starts at zero and always increases but Y=0 may either
1613 indicate the top of the window or the bottom depending on the fragment
1614 coordinate origin convention (see TGSI_PROPERTY_FS_COORD_ORIGIN).
1615 The Z coordinate ranges from 0 to 1 to represent depth from the front
1616 to the back of the Z buffer. The W component contains the reciprocol
1617 of the interpolated vertex position W component.
1619 Fragment shaders may also declare an output register with
1620 TGSI_SEMANTIC_POSITION. Only the Z component is writable. This allows
1621 the fragment shader to change the fragment's Z position.
1628 For vertex shader outputs or fragment shader inputs/outputs, this
1629 label indicates that the resister contains an R,G,B,A color.
1631 Several shader inputs/outputs may contain colors so the semantic index
1632 is used to distinguish them. For example, color[0] may be the diffuse
1633 color while color[1] may be the specular color.
1635 This label is needed so that the flat/smooth shading can be applied
1636 to the right interpolants during rasterization.
1640 TGSI_SEMANTIC_BCOLOR
1641 """"""""""""""""""""
1643 Back-facing colors are only used for back-facing polygons, and are only valid
1644 in vertex shader outputs. After rasterization, all polygons are front-facing
1645 and COLOR and BCOLOR end up occupying the same slots in the fragment shader,
1646 so all BCOLORs effectively become regular COLORs in the fragment shader.
1652 Vertex shader inputs and outputs and fragment shader inputs may be
1653 labeled with TGSI_SEMANTIC_FOG to indicate that the register contains
1654 a fog coordinate in the form (F, 0, 0, 1). Typically, the fragment
1655 shader will use the fog coordinate to compute a fog blend factor which
1656 is used to blend the normal fragment color with a constant fog color.
1658 Only the first component matters when writing from the vertex shader;
1659 the driver will ensure that the coordinate is in this format when used
1660 as a fragment shader input.
1666 Vertex shader input and output registers may be labeled with
1667 TGIS_SEMANTIC_PSIZE to indicate that the register contains a point size
1668 in the form (S, 0, 0, 1). The point size controls the width or diameter
1669 of points for rasterization. This label cannot be used in fragment
1672 When using this semantic, be sure to set the appropriate state in the
1673 :ref:`rasterizer` first.
1676 TGSI_SEMANTIC_GENERIC
1677 """""""""""""""""""""
1679 All vertex/fragment shader inputs/outputs not labeled with any other
1680 semantic label can be considered to be generic attributes. Typical
1681 uses of generic inputs/outputs are texcoords and user-defined values.
1684 TGSI_SEMANTIC_NORMAL
1685 """"""""""""""""""""
1687 Indicates that a vertex shader input is a normal vector. This is
1688 typically only used for legacy graphics APIs.
1694 This label applies to fragment shader inputs only and indicates that
1695 the register contains front/back-face information of the form (F, 0,
1696 0, 1). The first component will be positive when the fragment belongs
1697 to a front-facing polygon, and negative when the fragment belongs to a
1698 back-facing polygon.
1701 TGSI_SEMANTIC_EDGEFLAG
1702 """"""""""""""""""""""
1704 For vertex shaders, this sematic label indicates that an input or
1705 output is a boolean edge flag. The register layout is [F, x, x, x]
1706 where F is 0.0 or 1.0 and x = don't care. Normally, the vertex shader
1707 simply copies the edge flag input to the edgeflag output.
1709 Edge flags are used to control which lines or points are actually
1710 drawn when the polygon mode converts triangles/quads/polygons into
1713 TGSI_SEMANTIC_STENCIL
1714 """"""""""""""""""""""
1716 For fragment shaders, this semantic label indicates than an output
1717 is a writable stencil reference value. Only the Y component is writable.
1718 This allows the fragment shader to change the fragments stencilref value.
1721 Declaration Sampler View
1722 ^^^^^^^^^^^^^^^^^^^^^^^^
1724 Follows Declaration token if file is TGSI_FILE_SAMPLER_VIEW.
1726 DCL SVIEW[#], resource, type(s)
1728 Declares a shader input sampler view and assigns it to a SVIEW[#]
1731 resource can be one of BUFFER, 1D, 2D, 3D, 1DArray and 2DArray.
1733 type must be 1 or 4 entries (if specifying on a per-component
1734 level) out of UNORM, SNORM, SINT, UINT and FLOAT.
1737 Declaration Resource
1738 ^^^^^^^^^^^^^^^^^^^^
1740 Follows Declaration token if file is TGSI_FILE_RESOURCE.
1742 DCL RES[#], resource
1744 Declares a shader input resource and assigns it to a RES[#]
1747 resource can be one of BUFFER, 1D, 2D, 3D, CUBE, 1DArray and
1752 ^^^^^^^^^^^^^^^^^^^^^^^^
1755 Properties are general directives that apply to the whole TGSI program.
1760 Specifies the fragment shader TGSI_SEMANTIC_POSITION coordinate origin.
1761 The default value is UPPER_LEFT.
1763 If UPPER_LEFT, the position will be (0,0) at the upper left corner and
1764 increase downward and rightward.
1765 If LOWER_LEFT, the position will be (0,0) at the lower left corner and
1766 increase upward and rightward.
1768 OpenGL defaults to LOWER_LEFT, and is configurable with the
1769 GL_ARB_fragment_coord_conventions extension.
1771 DirectX 9/10 use UPPER_LEFT.
1773 FS_COORD_PIXEL_CENTER
1774 """""""""""""""""""""
1776 Specifies the fragment shader TGSI_SEMANTIC_POSITION pixel center convention.
1777 The default value is HALF_INTEGER.
1779 If HALF_INTEGER, the fractionary part of the position will be 0.5
1780 If INTEGER, the fractionary part of the position will be 0.0
1782 Note that this does not affect the set of fragments generated by
1783 rasterization, which is instead controlled by gl_rasterization_rules in the
1786 OpenGL defaults to HALF_INTEGER, and is configurable with the
1787 GL_ARB_fragment_coord_conventions extension.
1789 DirectX 9 uses INTEGER.
1790 DirectX 10 uses HALF_INTEGER.
1792 FS_COLOR0_WRITES_ALL_CBUFS
1793 """"""""""""""""""""""""""
1794 Specifies that writes to the fragment shader color 0 are replicated to all
1795 bound cbufs. This facilitates OpenGL's fragColor output vs fragData[0] where
1796 fragData is directed to a single color buffer, but fragColor is broadcast.
1799 """"""""""""""""""""""""""
1800 If this property is set on the program bound to the shader stage before the
1801 fragment shader, user clip planes should have no effect (be disabled) even if
1802 that shader does not write to any clip distance outputs and the rasterizer's
1803 clip_plane_enable is non-zero.
1804 This property is only supported by drivers that also support shader clip
1806 This is useful for APIs that don't have UCPs and where clip distances written
1807 by a shader cannot be disabled.
1810 Texture Sampling and Texture Formats
1811 ------------------------------------
1813 This table shows how texture image components are returned as (x,y,z,w) tuples
1814 by TGSI texture instructions, such as :opcode:`TEX`, :opcode:`TXD`, and
1815 :opcode:`TXP`. For reference, OpenGL and Direct3D conventions are shown as
1818 +--------------------+--------------+--------------------+--------------+
1819 | Texture Components | Gallium | OpenGL | Direct3D 9 |
1820 +====================+==============+====================+==============+
1821 | R | (r, 0, 0, 1) | (r, 0, 0, 1) | (r, 1, 1, 1) |
1822 +--------------------+--------------+--------------------+--------------+
1823 | RG | (r, g, 0, 1) | (r, g, 0, 1) | (r, g, 1, 1) |
1824 +--------------------+--------------+--------------------+--------------+
1825 | RGB | (r, g, b, 1) | (r, g, b, 1) | (r, g, b, 1) |
1826 +--------------------+--------------+--------------------+--------------+
1827 | RGBA | (r, g, b, a) | (r, g, b, a) | (r, g, b, a) |
1828 +--------------------+--------------+--------------------+--------------+
1829 | A | (0, 0, 0, a) | (0, 0, 0, a) | (0, 0, 0, a) |
1830 +--------------------+--------------+--------------------+--------------+
1831 | L | (l, l, l, 1) | (l, l, l, 1) | (l, l, l, 1) |
1832 +--------------------+--------------+--------------------+--------------+
1833 | LA | (l, l, l, a) | (l, l, l, a) | (l, l, l, a) |
1834 +--------------------+--------------+--------------------+--------------+
1835 | I | (i, i, i, i) | (i, i, i, i) | N/A |
1836 +--------------------+--------------+--------------------+--------------+
1837 | UV | XXX TBD | (0, 0, 0, 1) | (u, v, 1, 1) |
1838 | | | [#envmap-bumpmap]_ | |
1839 +--------------------+--------------+--------------------+--------------+
1840 | Z | XXX TBD | (z, z, z, 1) | (0, z, 0, 1) |
1841 | | | [#depth-tex-mode]_ | |
1842 +--------------------+--------------+--------------------+--------------+
1843 | S | (s, s, s, s) | unknown | unknown |
1844 +--------------------+--------------+--------------------+--------------+
1846 .. [#envmap-bumpmap] http://www.opengl.org/registry/specs/ATI/envmap_bumpmap.txt
1847 .. [#depth-tex-mode] the default is (z, z, z, 1) but may also be (0, 0, 0, z)
1848 or (z, z, z, z) depending on the value of GL_DEPTH_TEXTURE_MODE.