ISA.xml 55.1 KB
 Alyssa Rosenzweig committed Jul 16, 2021 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 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1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499  This immediates are accessible in (almost) any instruction, provided the immediate mode is kept to the default. They optimize for the most common immediate values; any immediate listed here may be used without taking up a uniform slot or a register. Most integer instructions can access separate half-words and individual bytes via swizzles on the source. 0x00000000 0xFFFFFFFF 0x7FFFFFFF 0xFAFCFDFE 0x01000000 0x80002000 0x70605030 0xC0B0A090 0x03020100 0x07060504 0x0B0A0908 0x0F0E0D0C 0x13121110 0x17161514 0x1B1A1918 0x1F1E1D1C 0x3F800000 0x3DCCCCCD 0x3EA2F983 0x3F317218 0x40490FDB 0x00000000 0x477FFF00 0x5C005BF8 0x2E660000 0x34000000 0x38000000 0x3C000000 0x40000000 0x44000000 0x48000000 0x42480000 Every Valhall instruction can perform an action, like wait on dependency slots. A few special actions are available, specified in the instruction metadata from this enum. The wait0126 action is required to wait on dependency slot #6 and should be set on the instruction immediately preceding ATEST. The barrier action may be set on any instruction for subgroup barriers, and should particularly be set with the BARRIER instruction for global barriers. The td action only applies to fragment shaders and is used to terminate helper invocations, it should be set as early as possible after helper invocations are no longer needed as determined by data flow analysis. The return action is used to terminate the shader, although it may be overloaded by the BLEND instruction. The reconverge action is required on any instruction immediately preceding a possible change to the mask of active threads in a subgroup. This includes all divergent branches, but it also includes the final instruction at the end of any basic block where the immediate successor (fallthrough) is the target of a divergent branch. wait0126 barrier reconverge td return Selects how immediates sources are interpreted. none ts id Situated between the immediates hard-coded in the hardware and the uniforms defined purely in software, Valhall has a some special "constants" passing through data structures. These are encoded like the table of immediates, as if special constant $i$ were lookup table entry $32 + i$. These special values are selected with the .ts modifier. tls_ptr tls_ptr_hi wls_ptr wls_ptr_hi Situated between the immediates hard-coded in the hardware and the uniforms defined purely in software, Valhall has a some special "constants" passing through data structures. These are encoded like the table of immediates, as if special constant $i$ were lookup table entry $32 + i$. These special values are selected with the .id modifier. lane_id core_id program_counter b0123 b3210 b0101 b2323 b0000 b1111 b2222 b3333 b2301 b1032 b0011 b2233 Used to select the 2 bytes for shifts of 16-bit vectors b02 b00 b11 b22 b33 b01 b23 h00 h10 h01 h11 b00 b20 b02 b22 b11 b31 b13 b33 b01 b23 none h0 h1 b0 b1 b2 b3 none h0 h1 b0 b1 b2 b3 w0 b0 b1 b2 b3 h0 h1 Corresponds to IEEE 754 rounding modes rte rtp rtn rtz Comparison instructions like FCMP return a boolean but may encode this boolean in a variety of ways. i1 gives a OpenGL style 0/1 boolean. m1 gives a Direct3D style 0/~0 boolean. f1 gives a floating-point 0.0f / 1.0f boolean. Switching between these modes is useful to fold a boolean type convert into a comparison. u1 is used internally to implement 64-bit comparisons. i1 f1 m1 u1 none h0 h1 Clamp applied to the destination of a floating-point instruction. Note the clamps may be decomposed as two independent bits for clamp_0_inf and clamp_m1_1, with clamp_0_1 arising as the composition of clamp_0_inf and clamp_m1_1 in either order. none clamp_0_inf clamp_m1_1 clamp_0_1 Condition code. Type must be inferred from the instruction. IEEE 754 total ordering only applies to floating point compares. "Not equal" and "greater than or less than" are distinguished by NaN behaviour conforming to the IEEE 754 specification. eq gt ge ne lt le gtlt total Texture dimension. 1d 2d 3d cube Level-of-detail selection mode in a texture instruction. zero computed explicit computed_bias grdesc Format of data loaded to / stored from registers for general memory access. f32 f16 u32 sr0 sr1 sr2 sr3 sr4 sr5 sr6 sr7 Number of channels loaded/stored for general memory access. none v2 v3 v4 Number of bits loaded/stored for general memory access. i8 i16 i24 i32 i48 i64 i96 i128 Dependency slot set on a message-passing instruction that writes to registers. Before reading the destination, a future instruction must wait on the specified slot. Slot #7 is for BARRIER instructions only. slot0 slot1 slot2 slot7 Memory segment written to by a STORE instruction. global pos vary tl Selects the effective subgroup size from subgroup operations. The hardware warps are sixteen threads on Valhall, but subdividing a warp may be useful for API requirements. In particular, derivatives may be calculated with quads (four threads). subgroup2 subgroup4 subgroup8 subgroup16 Acts as a modifier on the lane specificier for a CLPER instruction. The accumulate mode is required for efficient subgroup reductions. none xor accumulate shift Accesses to inactive lanes (due to divergence) in a subgroup is generally undefined in APIs. However, the results of permuting with an inactive lane with CLPER.i32 are well-defined in Valhall: they return one of the following values, as specified in the CLPER.i32 instructions. Sometimes certain values enable small optimizations. zero umax i1 v2i1 smin smax v2smin v2smax v4smin v4smax f1 v2f1 infn inf v2infn v2inf Do nothing. Useful at the start of a block for waiting on slots required by the first actual instruction of the block, to reconcile dependencies after a branch. Also useful as the sole instruction of an empty shader. Branches to a specified relative offset if its source is nonzero (default) or if its source is zero (if .eq is set). The offset is 27-bits and sign-extended, giving an effective range of ±26-bits. The offset is specified in units of instructions, relative to the *next* instruction. Positive offsets may be interpreted as "number of instructions to skip". Since Valhall instructions are 8 bytes, this operates as: $$PC := \begin{cases} PC + 8 \cdot (\text{offset} \; + 1) & \text{if} \; \text{src} \stackrel{?}{=} 0 \\ PC + 8 & \text{otherwise} \end{cases}$$ Used with comparison instructions to implement control flow. Tie the source to a nonzero constant to implement a jump. May introduce divergence, so generally requires .reconverge flow control. Value to compare against zero Evaluates the given condition, and if it passes, discards the current fragment and terminates the thread. The destination should be set to R60. Only valid in a frgment shader. Updated coverage mask (set to R60) Left value to compare Right value to compare Jump to an indirectly specified address. Used to jump to blend shaders at the end of a fragment shader. Value to compare against zero Branch target General-purpose barrier. Must use slot #7. Must be paired with a .barrier action on the instruction. Evaluates the given condition and outputs either the true source or the false source. Left value to compare Right value to compare Return value if true Return value if false Evaluates the given condition and outputs either the true source or the false source. Valhall lacks integer minimum/maximum instructions. CSEL instructions with tied operands form the canonical implementations of these instructions. Similarly, the integer $\text{sign}$ function is canonically implemented with a pair of CSEL instructions. Left value to compare Right value to compare Return value if true Return value if false Interpolates a given varying Vertex ID Instance ID The index must not diverge within a warp. Vertex ID Instance ID Index Loads the effective address of the position buffer (in a position shader) or the varying buffer (in a varying shader). That is, the base pointer plus the vertex's linear ID (the first source) times the buffer's per-vertex stride. LEA_ATTR should be executed once in a position/varying shader, with the linear ID preloaded as r59. Each position/varying store can then be constructed as STORE with the base address sourced from the 64-bit destination of LEA_ATTR and an appropriately computed offset. Varying stores bypass the usual conversion hardware for attributes; this diverges from earlier Mali hardware. Linear ID Loads from main memory Address to load from after adding offset Stores to main memory Address to store to after adding offset Stores to images Address to store to after adding offset Loads a given render target, specified in the pixel indices descriptor, at a given location and sample, and convert to the format specified in the internal conversion descriptor. Used to implement EXT_framebuffer_fetch and internally in blend shaders. Pixel indices descriptor Coverage mask Conversion descriptor Blends a given render target. This loads the API-specified blend state for the render target from the first source. Blend descriptors are available as special immediates. It then reads the colour to be blended from the first staging register, with the specified vector size and register format as desired. The resulting coverage mask is stored to the second set of staging registers. In the fixed-function path, BLEND sends the colour to the blender to be written to the tilebuffer. Then, if the instruction's flow control specifies termination, the fragment program is ended. If it does not specify termination, BLEND acts as a relative branch, branching with the offset specified as target. This allows the subsequent instructions to be skipped when fixed-function blending is used. Note this implicit branch can never introduce divergence, so .reconverge is not required. In the blend shader path, BLEND ignores the specified flow control and does not branch to the specified offset. Instead, execution considers normally with the next instruction. The compiler should insert code for calling a blend shader after the BLEND instruction unless it is known that a blend shader will never be required. The indirection is required to support both fixed-function and blend shaders efficiently and without shader variants. Blend descriptor Does alpha-to-coverage testing, updating the sample coverage mask. ATEST does not do an implicit discard. It should be executed before the first ZS_EMIT or BLEND instruction. Updated coverage mask Input coverage mask Alpha value (render target 0) Programatically writes out depth, stencil, or both, depending on which modifiers are set. Used to implement gl_FragDepth and gl_FragStencil. Updated coverage mask Depth value Stencil value Input coverage mask Performs the given data conversion. Note that floating-point rounding is handled via the same hardware and therefore shares an encoding. Round mode is specified where it makes sense. Value to convert Converts up with the specified round mode. Value to convert Performs the given data conversion. Value to convert Performs the given rounding, using the convert unit. Value to convert Canonical register-to-register move. Used as a primitive for various bitwise operations. Used as a primitive for various bitwise operations. Used as a primitive for various bitwise operations. 64-bit abs may be constructed in 4 instructions (5 clocks) by checking the sign with ICMP.s32.lt.m1 hi, 0 and negating based on the result with IADD.s64 and LSHIFT_XOR.i32 on each half. Only available as 32-bit. Smaller bitsizes require explicit conversions. 64-bit popcount may be constructed in 3 clocks by separate 32-bit popcounts of each half and a 32-bit add, which is guaranteed not to overflow. Only available as 32-bit. Other bitsizes may be derived with swizzles. For fully featured bitwise operation, see the shift opcodes. For fully featured bitwise operation, see the shift opcodes. Returns the mask of lanes ever active within the warp (subgroup), such that the source is nonzero. The number of work-items in a subgroup is given as the popcount of this value with a nonzero input. An all() subgroup operation may be constructed as WMASK of the input compared for equality with WMASK of an nonzero value. An any() subgroup operation may be constructed as WMASK of the input compared against zero. Breaks up the floating-point input into its fractional (mantissa) and exponent parts. By default, this is compatible with the frexp() function in APIs. With the log modifier, the floating point format is adjusted to be compatible with Valhall's argument reduction for logarithm computation. Performs a given special function. The floating-point reciprocal (FRCP) and reciprocal square root (FRSQ) instructions may be freely used as-is. The trigonometric tables (FSIN_TABLE.u6 and FCOS_TABLE.u6) are crude, requiring both an argument reduction and postprocessing. Likewise the logarithm instruction (FLOGD.f32) requires an argument reduction. See the transcendentals section for more information. $A + B$ A B $\min \{ A, B \}$ A B $\max \{ A, B \}$ A B Given a pair of 32-bit floats, output a pair of 16-bit floats packed into a 32-bit destination. A B Computes $A \cdot 2^B$ by adding B to the exponent of A. Used to calculate various special functions, particularly base-2 exponents. Special case handling differs from an actual floating-point multiply, so this should not be used outside fixed instruction sequences. A B Calculates the base-2 exponent of an argument specified as a 8:24 fixed-point. The original argument is passed as well for correct handling of special cases. Input as 8:24 fixed-point Input as 32-bit float Performs a floating-point addition specialized for logarithm computation. A B $A + B$ with optional saturation. As Valhall lacks swizzle instructions, IADD.v2i16 with zero is the canonical lowering for swizzles. A B Calculates $A | (B \ll 16)$. Used to implement (ushort2)(A, B) A B $A - B$ with optional saturation A B Sign or zero extend B to 64-bits, left-shift by shift, and add the 64-bit value A. These instructions accelerate address arithmetic, but may be used in full generality for 64-bit integer arithmetic. A B $A \cdot B$ with optional saturation. Note the multipliers can only handle up to 32-bit by 32-bit multiplies. The 64-bit "multiply" acts like IMUL.u32 but additionally writes the high half of the product to the high half of the 64-bit destination. Along with IADD.u32 and IADD.u64, this allows the construction of a 64-bit multiply in 5 instructions (6 clocks). A B A B $(A + B) \gg 1$ without intermediate overflow, corresponding to hadd() in OpenCL. With the .rhadd modifier set, it instead calculates $(A + B + 1) \gg 1$ corresponding to rhadd() in OpenCL. Selects the value of A in the subgroup lane given by B. This implements subgroup broadcasts. It may be used as a primitive for screen space derivatives in fragment shaders. A B $A \cdot B + C$ A B C Left shifts its first source by a specified amount and bitwise ANDs it with the second source, optionally inverting the second source or the result. A shift B Right shifts its first source by a specified amount and bitwise ANDs it with the second source, optionally inverting the second source or the result. A shift B Left shifts its first source by a specified amount and bitwise ORs it with the second source, optionally inverting the second source or the result. A shift B Right shifts its first source by a specified amount and bitwise ORs it with the second source, optionally inverting the second source or the result. A shift B Left shifts its first source by a specified amount and bitwise XORs it with the second source, optionally inverting the second source or the result. A shift B Right shifts its first source by a specified amount and bitwise XORs it with the second source, optionally inverting the second source or the result. A shift B Mux between A and B based on the provided mask. Equivalent to bitselect() in OpenCL. (A & mask) | (A & ~mask) A B Mask During a cube map transform, select the S coordinate given a selected face. Z coordinate as 32-bit floating point X coordinate as 32-bit floating point Cube face index During a cube map transform, select the T coordinate given a selected face. Y coordinate as 32-bit floating point Z coordinate as 32-bit floating point Cube face index Calculates $A | (B \ll 8) | (CD \ll 16)$ for 8-bit A and B and 16-bit CD. To implement (uchar4) (A, B, C, D) in full generality, use the sequence MKVEC.v4i8 CD, C, D, #0; MKVEC.v4i8 out, A, B, CD MKVEC.v4i8 also allows zero extending arbitrary 8-bit lanes. For example, to extend r0.b3 to r1, use MKVEC.v4i8 r1, r0.b3, 0x0.b0, 0x0. A B CD Select the maximum absolute value of its arguments. X coordinate as 32-bit floating point Y coordinate as 32-bit floating point Z coordinate as 32-bit floating point Select the cube face index corresponding to the arguments. X coordinate as 32-bit floating point Y coordinate as 32-bit floating point Z coordinate as 32-bit floating point 8-bit integer dot product between 4 channel vectors, intended for machine learning. Available in both unsigned and signed variants, controlling sign-extension/zero-extension behaviour to the final 32-bit destination. Saturation is available. Corresponds to the cl_arm_integer_dot_product_* family of OpenCL extensions. Not for actual use, just for completeness. Instead, use your platform's neural accelerator. For $A, B \in \{ 0, \ldots, 255 \}^4$ and $\text{Accumulator} \in \mathbb{Z}$, calculates $(A \cdot B) + \text{Accumulator}$ and optionally saturates. A B Accumulator Evaluates the given condition, do a logical and/or with the condition in the result source, and return in the given result type (integer one, integer minus one, or floating-point one). The third source is useful for chaining together conditions without intermediate bitwise arithmetic; when this is not desired, tie it to zero and use the OR combine mode (do not set the .and modifier). The sequence modifier .seq is used to construct 64-bit compares in 2 ICMP.u32 instructions, in conjunction with the u1 result type on the low half, the m1 result type on the high half, and the result of the low half comparison passed as the third source. For comparisons other than 64-bit, do not set the .seq modifier and do not use the u1 result type. A B C Evaluates the given condition, do a logical and/or with the condition in the result source, and return in the given result type (integer one, integer minus one, or floating-point one). The third source is useful for chaining together conditions without intermediate bitwise arithmetic; when this is not desired, tie it to zero and use the OR combine mode (do not set the .and modifier). A B C Evaluates the given condition, do a logical and/or with the condition in the result source, and return in the given result type (integer one, integer minus one, or floating-point one). The third source is useful for chaining together conditions without intermediate bitwise arithmetic; when this is not desired, tie it to zero and use the OR combine mode (do not set the .and modifier). The sequence modifier .seq is used to construct signed 64-bit compares in 1 ICMP.u32 and 1 ICMP.s32 instruction, in conjunction with the u1 result type on the low half, the m1 result type on the high half, and the result of the low half comparison passed as the third source. For comparisons other than 64-bit, do not set the .seq modifier and do not use the u1 result type. A B C Adds an arbitrary 32-bit immediate embedded within the instruction stream. If no modifiers are required, this is preferred to IADD.i32 with a constant accessed as a uniform. However, if the constant is available inline, IADD.f32 is preferred. IADD_IMM.i32 with the source tied to zero is the canonical immediate move. A Adds an arbitrary pair of 16-bit immediates embedded within the instruction stream. If no modifiers are required, this is preferred to IADD.v2i16 with a constant accessed as a uniform. However, if the constant is available inline, IADD.v2i16 is preferred. Adding only a single 16-bit constant requires replication of the constant. A Adds an arbitrary quad of 8-bit immediates embedded within the instruction stream. If no modifiers are required, this is preferred to IADD.v4i8 with a constant accessed as a uniform. However, if the constant is available inline, IADD.v4i8 is preferred. Adding only a single 8-bit constant requires replication of the constant. A Adds an arbitrary 32-bit immediate embedded within the instruction stream. If no modifiers are required, this is preferred to FADD.f32 with a constant accessed as a uniform. However, if the constant is available inline, FADD.f32 is preferred. A Adds an arbitrary pair of 16-bit immediates embedded within the instruction stream. If no modifiers are required, this is preferred to FADD.v2f16 with a constant accessed as a uniform. However, if the constant is available inline, FADD.v2f16 is preferred. Adding only a single 16-bit constant requires replication of the constant. A Unfiltered textured instruction. Image to read from Ordinary texturing instruction using a sampler. Image to read from Only works for FP32 varyings. Image to read from First calculates $A \cdot B + C$ and then biases the exponent by D. Used in special transcendental function sequences. It should not be used for general code as its special case handling differs from two back-to-back FMA.f32 operations. Equivalent to FMA.f32 back-to-back with RSCALE.f32 A B C D