/* * Copyright (C) 2019 Connor Abbott * Copyright (C) 2019 Lyude Paul * Copyright (C) 2019 Ryan Houdek * * Permission is hereby granted, free of charge, to any person obtaining a * copy of this software and associated documentation files (the "Software"), * to deal in the Software without restriction, including without limitation * the rights to use, copy, modify, merge, publish, distribute, sublicense, * and/or sell copies of the Software, and to permit persons to whom the * Software is furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice (including the next * paragraph) shall be included in all copies or substantial portions of the * Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ #ifndef __bifrost_h__ #define __bifrost_h__ #include #include #include #include #ifdef __cplusplus extern "C" { #endif #define BIFROST_DBG_MSGS 0x0001 #define BIFROST_DBG_SHADERS 0x0002 #define BIFROST_DBG_SHADERDB 0x0004 #define BIFROST_DBG_VERBOSE 0x0008 #define BIFROST_DBG_INTERNAL 0x0010 #define BIFROST_DBG_NOSCHED 0x0020 #define BIFROST_DBG_INORDER 0x0040 #define BIFROST_DBG_NOVALIDATE 0x0080 #define BIFROST_DBG_NOOPT 0x0100 #define BIFROST_DBG_NOIDVS 0x0200 #define BIFROST_DBG_NOSB 0x0400 #define BIFROST_DBG_NOPRELOAD 0x0800 #define BIFROST_DBG_SPILL 0x1000 #define BIFROST_DBG_NOPSCHED 0x2000 extern int bifrost_debug; enum bifrost_message_type { BIFROST_MESSAGE_NONE = 0, BIFROST_MESSAGE_VARYING = 1, BIFROST_MESSAGE_ATTRIBUTE = 2, BIFROST_MESSAGE_TEX = 3, BIFROST_MESSAGE_VARTEX = 4, BIFROST_MESSAGE_LOAD = 5, BIFROST_MESSAGE_STORE = 6, BIFROST_MESSAGE_ATOMIC = 7, BIFROST_MESSAGE_BARRIER = 8, BIFROST_MESSAGE_BLEND = 9, BIFROST_MESSAGE_TILE = 10, /* type 11 reserved */ BIFROST_MESSAGE_Z_STENCIL = 12, BIFROST_MESSAGE_ATEST = 13, BIFROST_MESSAGE_JOB = 14, BIFROST_MESSAGE_64BIT = 15 }; enum bifrost_ftz { BIFROST_FTZ_DISABLE = 0, BIFROST_FTZ_DX11 = 1, BIFROST_FTZ_ALWAYS = 2, BIFROST_FTZ_ABRUPT = 3 }; enum bifrost_exceptions { BIFROST_EXCEPTIONS_ENABLED = 0, BIFROST_EXCEPTIONS_DISABLED = 1, BIFROST_EXCEPTIONS_PRECISE_DIVISION = 2, BIFROST_EXCEPTIONS_PRECISE_SQRT = 3, }; /* Describes clause flow control, with respect to control flow and branch * reconvergence. * * Control flow may be considered back-to-back (execute clauses back-to-back), * non-back-to-back (switch warps after clause before the next clause), write * elision (back-to-back and elide register slot #3 write from the clause), or * end of shader. * * Branch reconvergence may be disabled, enabled unconditionally, or enabled * based on the program counter. A clause requires reconvergence if it has a * successor that can be executed without first executing the clause itself. * Separate iterations of a loop are treated separately here, so it is also the * case for a loop exit where the iteration count is not warp-invariant. * */ enum bifrost_flow { /* End-of-shader */ BIFROST_FLOW_END = 0, /* Non back-to-back, PC-encoded reconvergence */ BIFROST_FLOW_NBTB_PC = 1, /* Non back-to-back, unconditional reconvergence */ BIFROST_FLOW_NBTB_UNCONDITIONAL = 2, /* Non back-to-back, no reconvergence */ BIFROST_FLOW_NBTB = 3, /* Back-to-back, unconditional reconvergence */ BIFROST_FLOW_BTB_UNCONDITIONAL = 4, /* Back-to-back, no reconvergence */ BIFROST_FLOW_BTB_NONE = 5, /* Write elision, unconditional reconvergence */ BIFROST_FLOW_WE_UNCONDITIONAL = 6, /* Write elision, no reconvergence */ BIFROST_FLOW_WE = 7, }; enum bifrost_slot { /* 0-5 are general purpose */ BIFROST_SLOT_ELDEST_DEPTH = 6, BIFROST_SLOT_ELDEST_COLOUR = 7, }; struct bifrost_header { /* Reserved */ unsigned zero1 : 5; /* Flush-to-zero mode, leave zero for GL */ enum bifrost_ftz flush_to_zero : 2; /* Convert any infinite result of any floating-point operation to the * biggest representable number */ unsigned suppress_inf : 1; /* Convert NaN to +0.0 */ unsigned suppress_nan : 1; /* Floating-point excception handling mode */ enum bifrost_exceptions float_exceptions : 2; /* Enum describing the flow control, which matters for handling * divergence and reconvergence efficiently */ enum bifrost_flow flow_control : 3; /* Reserved */ unsigned zero2 : 1; /* Terminate discarded threads, rather than continuing execution. Set * for fragment shaders for standard GL behaviour of DISCARD. Also in a * fragment shader, this disables helper invocations, so cannot be used * in a shader that requires derivatives or texture LOD computation */ unsigned terminate_discarded_threads : 1; /* If set, the hardware may prefetch the next clause. If false, the * hardware may not. Clear for unconditional branches. */ unsigned next_clause_prefetch : 1; /* If set, a barrier will be inserted after the clause waiting for all * message passing instructions to read their staging registers, such * that it is safe for the next clause to write them. */ unsigned staging_barrier : 1; unsigned staging_register : 6; /* Slots to wait on and slot to be used for message passing * instructions respectively */ unsigned dependency_wait : 8; unsigned dependency_slot : 3; enum bifrost_message_type message_type : 5; enum bifrost_message_type next_message_type : 5; } __attribute__((packed)); enum bifrost_packed_src { BIFROST_SRC_PORT0 = 0, BIFROST_SRC_PORT1 = 1, BIFROST_SRC_PORT2 = 2, BIFROST_SRC_STAGE = 3, BIFROST_SRC_FAU_LO = 4, BIFROST_SRC_FAU_HI = 5, BIFROST_SRC_PASS_FMA = 6, BIFROST_SRC_PASS_ADD = 7, }; struct bifrost_fma_inst { unsigned src0 : 3; unsigned op : 20; } __attribute__((packed)); struct bifrost_add_inst { unsigned src0 : 3; unsigned op : 17; } __attribute__((packed)); enum branch_bit_size { BR_SIZE_32 = 0, BR_SIZE_16XX = 1, BR_SIZE_16YY = 2, // For the above combinations of bitsize and location, an extra bit is // encoded via comparing the sources. The only possible source of ambiguity // would be if the sources were the same, but then the branch condition // would be always true or always false anyways, so we can ignore it. But // this no longer works when comparing the y component to the x component, // since it's valid to compare the y component of a source against its own // x component. Instead, the extra bit is encoded via an extra bitsize. BR_SIZE_16YX0 = 3, BR_SIZE_16YX1 = 4, BR_SIZE_32_AND_16X = 5, BR_SIZE_32_AND_16Y = 6, // Used for comparisons with zero and always-true, see below. I think this // only works for integer comparisons. BR_SIZE_ZERO = 7, }; struct bifrost_regs { unsigned fau_idx : 8; unsigned reg3 : 6; unsigned reg2 : 6; unsigned reg0 : 5; unsigned reg1 : 6; unsigned ctrl : 4; } __attribute__((packed)); #define BIFROST_FMTC_CONSTANTS 0b0011 #define BIFROST_FMTC_FINAL 0b0111 struct bifrost_fmt_constant { unsigned pos : 4; unsigned tag : 4; uint64_t imm_1 : 60; uint64_t imm_2 : 60; } __attribute__((packed)); /* Clause formats, encoded in a table */ enum bi_clause_subword { /* Literal 3-bit values */ BI_CLAUSE_SUBWORD_LITERAL_0 = 0, /* etc */ BI_CLAUSE_SUBWORD_LITERAL_7 = 7, /* The value of the corresponding tuple in the corresponding bits */ BI_CLAUSE_SUBWORD_TUPLE_0 = 8, /* etc */ BI_CLAUSE_SUBWORD_TUPLE_7 = 15, /* Clause header */ BI_CLAUSE_SUBWORD_HEADER = 16, /* Leave zero, but semantically distinct from literal 0 */ BI_CLAUSE_SUBWORD_RESERVED = 17, /* Embedded constant 0 */ BI_CLAUSE_SUBWORD_CONSTANT = 18, /* M bits controlling modifier for the constant */ BI_CLAUSE_SUBWORD_M = 19, /* Z bit: 1 to begin encoding constants, 0 to terminate the clause */ BI_CLAUSE_SUBWORD_Z = 20, /* Upper 3-bits of a given tuple and zero extended */ BI_CLAUSE_SUBWORD_UPPER_0 = 32, /* etc */ BI_CLAUSE_SUBWORD_UPPER_7 = BI_CLAUSE_SUBWORD_UPPER_0 + 7, /* Upper 3-bits of two tuples, concatenated and zero-extended */ BI_CLAUSE_SUBWORD_UPPER_23 = BI_CLAUSE_SUBWORD_UPPER_0 + 23, BI_CLAUSE_SUBWORD_UPPER_56 = BI_CLAUSE_SUBWORD_UPPER_0 + 56, }; #define L(x) ((enum bi_clause_subword)(BI_CLAUSE_SUBWORD_LITERAL_0 + x)) #define U(x) ((enum bi_clause_subword)(BI_CLAUSE_SUBWORD_UPPER_0 + x)) #define T(x) ((enum bi_clause_subword)(BI_CLAUSE_SUBWORD_TUPLE_0 + x)) #define EC BI_CLAUSE_SUBWORD_CONSTANT #define M BI_CLAUSE_SUBWORD_M #define Z BI_CLAUSE_SUBWORD_Z #define H BI_CLAUSE_SUBWORD_HEADER #define R BI_CLAUSE_SUBWORD_RESERVED struct bi_clause_format { unsigned format; /* format number */ unsigned pos; /* index in the clause */ enum bi_clause_subword tag_1; /* 2-bits */ enum bi_clause_subword tag_2; /* 3-bits */ enum bi_clause_subword tag_3; /* 3-bits */ enum bi_clause_subword s0_s3; /* 60 bits */ enum bi_clause_subword s4; /* 15 bits */ enum bi_clause_subword s5_s6; /* 30 bits */ enum bi_clause_subword s7; /* 15 bits */ }; /* clang-format off */ static const struct bi_clause_format bi_clause_formats[] = { { 0, 0, L(0), L(5), U(0), T(0), T(0), H, H }, { 0, 0, Z, L(1), U(0), T(0), T(0), H, H }, { 1, 1, Z, L(0), L(3), T(1), T(1), R, U(1) }, { 2, 1, L(0), L(4), U(1), T(1), T(1), T(2), T(2) }, { 3, 2, Z, L(0), L(4), EC, M, T(2), U(2) }, { 4, 2, L(0), L(0), L(1), T(3), T(3), T(2), U(23) }, { 4, 2, Z, L(0), L(5), T(3), T(3), T(2), U(23) }, { 5, 2, L(2), U(3), U(2), T(3), T(3), T(2), EC }, { 6, 3, Z, L(2), U(4), T(4), T(4), EC, EC }, { 7, 3, L(1), L(4), U(4), T(4), T(4), T(5), T(5) }, { 8, 4, Z, L(0), L(6), EC, M, T(5), U(5) }, { 9, 4, Z, L(0), L(7), T(6), T(6), T(5), U(56) }, { 10, 4, L(3), U(6), U(5), T(6), T(6), T(5), EC }, { 11, 5, Z, L(3), U(7), T(7), T(7), EC, EC }, }; /* clang-format on */ #undef L #undef U #undef T #undef EC #undef M #undef Z #undef H #undef R /* 32-bit modes for slots 2/3, as encoded in the register block. Other values * are reserved. First part specifies behaviour of slot 2 (Idle, Read, Write * Full, Write Low, Write High), second part behaviour of slot 3, and the last * part specifies the source for the write (FMA, ADD, or MIX for FMA/ADD). * * IDLE is a special mode disabling both slots, except for the first * instruction in the clause which uses IDLE_1 for the same purpose. * * All fields 0 used as sentinel for reserved encoding, so IDLE(_1) have FMA * set (and ignored) as a placeholder to differentiate from reserved. */ enum bifrost_reg_mode { BIFROST_R_WL_FMA = 1, BIFROST_R_WH_FMA = 2, BIFROST_R_W_FMA = 3, BIFROST_R_WL_ADD = 4, BIFROST_R_WH_ADD = 5, BIFROST_R_W_ADD = 6, BIFROST_WL_WL_ADD = 7, BIFROST_WL_WH_ADD = 8, BIFROST_WL_W_ADD = 9, BIFROST_WH_WL_ADD = 10, BIFROST_WH_WH_ADD = 11, BIFROST_WH_W_ADD = 12, BIFROST_W_WL_ADD = 13, BIFROST_W_WH_ADD = 14, BIFROST_W_W_ADD = 15, BIFROST_IDLE_1 = 16, BIFROST_I_W_FMA = 17, BIFROST_I_WL_FMA = 18, BIFROST_I_WH_FMA = 19, BIFROST_R_I = 20, BIFROST_I_W_ADD = 21, BIFROST_I_WL_ADD = 22, BIFROST_I_WH_ADD = 23, BIFROST_WL_WH_MIX = 24, BIFROST_WH_WL_MIX = 26, BIFROST_IDLE = 27, }; enum bifrost_reg_op { BIFROST_OP_IDLE = 0, BIFROST_OP_READ = 1, BIFROST_OP_WRITE = 2, BIFROST_OP_WRITE_LO = 3, BIFROST_OP_WRITE_HI = 4, }; struct bifrost_reg_ctrl_23 { enum bifrost_reg_op slot2; enum bifrost_reg_op slot3; bool slot3_fma; }; /* clang-format off */ #ifndef __cplusplus static const struct bifrost_reg_ctrl_23 bifrost_reg_ctrl_lut[32] = { [BIFROST_R_WL_FMA] = { BIFROST_OP_READ, BIFROST_OP_WRITE_LO, true }, [BIFROST_R_WH_FMA] = { BIFROST_OP_READ, BIFROST_OP_WRITE_HI, true }, [BIFROST_R_W_FMA] = { BIFROST_OP_READ, BIFROST_OP_WRITE, true }, [BIFROST_R_WL_ADD] = { BIFROST_OP_READ, BIFROST_OP_WRITE_LO, false }, [BIFROST_R_WH_ADD] = { BIFROST_OP_READ, BIFROST_OP_WRITE_HI, false }, [BIFROST_R_W_ADD] = { BIFROST_OP_READ, BIFROST_OP_WRITE, false }, [BIFROST_WL_WL_ADD] = { BIFROST_OP_WRITE_LO, BIFROST_OP_WRITE_LO, false }, [BIFROST_WL_WH_ADD] = { BIFROST_OP_WRITE_LO, BIFROST_OP_WRITE_HI, false }, [BIFROST_WL_W_ADD] = { BIFROST_OP_WRITE_LO, BIFROST_OP_WRITE, false }, [BIFROST_WH_WL_ADD] = { BIFROST_OP_WRITE_HI, BIFROST_OP_WRITE_LO, false }, [BIFROST_WH_WH_ADD] = { BIFROST_OP_WRITE_HI, BIFROST_OP_WRITE_HI, false }, [BIFROST_WH_W_ADD] = { BIFROST_OP_WRITE_HI, BIFROST_OP_WRITE, false }, [BIFROST_W_WL_ADD] = { BIFROST_OP_WRITE, BIFROST_OP_WRITE_LO, false }, [BIFROST_W_WH_ADD] = { BIFROST_OP_WRITE, BIFROST_OP_WRITE_HI, false }, [BIFROST_W_W_ADD] = { BIFROST_OP_WRITE, BIFROST_OP_WRITE, false }, [BIFROST_IDLE_1] = { BIFROST_OP_IDLE, BIFROST_OP_IDLE, true }, [BIFROST_I_W_FMA] = { BIFROST_OP_IDLE, BIFROST_OP_WRITE, true }, [BIFROST_I_WL_FMA] = { BIFROST_OP_IDLE, BIFROST_OP_WRITE_LO, true }, [BIFROST_I_WH_FMA] = { BIFROST_OP_IDLE, BIFROST_OP_WRITE_HI, true }, [BIFROST_R_I] = { BIFROST_OP_READ, BIFROST_OP_IDLE, false }, [BIFROST_I_W_ADD] = { BIFROST_OP_IDLE, BIFROST_OP_WRITE, false }, [BIFROST_I_WL_ADD] = { BIFROST_OP_IDLE, BIFROST_OP_WRITE_LO, false }, [BIFROST_I_WH_ADD] = { BIFROST_OP_IDLE, BIFROST_OP_WRITE_HI, false }, [BIFROST_WL_WH_MIX] = { BIFROST_OP_WRITE_LO, BIFROST_OP_WRITE_HI, false }, [BIFROST_WH_WL_MIX] = { BIFROST_OP_WRITE_HI, BIFROST_OP_WRITE_LO, false }, [BIFROST_IDLE] = { BIFROST_OP_IDLE, BIFROST_OP_IDLE, true }, }; #endif /* clang-format on */ /* Texture operator descriptors in various states. Usually packed in the * compiler and stored as a constant */ enum bifrost_texture_operation_mode { /* Dual texturing */ BIFROST_TEXTURE_OPERATION_DUAL = 1, /* Single texturing */ BIFROST_TEXTURE_OPERATION_SINGLE = 3, }; enum bifrost_index { /* Both texture/sampler index immediate */ BIFROST_INDEX_IMMEDIATE_SHARED = 0, /* Sampler index immediate, texture index from staging */ BIFROST_INDEX_IMMEDIATE_SAMPLER = 1, /* Texture index immediate, sampler index from staging */ BIFROST_INDEX_IMMEDIATE_TEXTURE = 2, /* Both indices from (separate) staging registers */ BIFROST_INDEX_REGISTER = 3, }; enum bifrost_tex_op { /* Given explicit derivatives, compute a gradient descriptor */ BIFROST_TEX_OP_GRDESC_DER = 4, /* Given implicit derivatives (texture coordinates in a fragment * shader), compute a gradient descriptor */ BIFROST_TEX_OP_GRDESC = 5, /* Fetch a texel. Takes a staging register with LOD level / face index * packed 16:16 */ BIFROST_TEX_OP_FETCH = 6, /* Filtered texture */ BIFROST_TEX_OP_TEX = 7, }; enum bifrost_lod_mode { /* Takes two staging registers forming a 64-bit gradient descriptor * (computed by a previous GRDESC or GRDESC_DER operation) */ BIFROST_LOD_MODE_GRDESC = 3, /* Take a staging register with 8:8 fixed-point in bottom 16-bits * specifying an explicit LOD */ BIFROST_LOD_MODE_EXPLICIT = 4, /* Takes a staging register with bottom 16-bits as 8:8 fixed-point LOD * bias and top 16-bit as 8:8 fixed-point lower bound (generally left * zero), added and clamped to a computed LOD */ BIFROST_LOD_MODE_BIAS = 5, /* Set LOD to zero */ BIFROST_LOD_MODE_ZERO = 6, /* Compute LOD */ BIFROST_LOD_MODE_COMPUTE = 7, }; enum bifrost_texture_format { /* 16-bit floating point, with optional clamping */ BIFROST_TEXTURE_FORMAT_F16 = 0, BIFROST_TEXTURE_FORMAT_F16_POS = 1, BIFROST_TEXTURE_FORMAT_F16_PM1 = 2, BIFROST_TEXTURE_FORMAT_F16_1 = 3, /* 32-bit floating point, with optional clamping */ BIFROST_TEXTURE_FORMAT_F32 = 4, BIFROST_TEXTURE_FORMAT_F32_POS = 5, BIFROST_TEXTURE_FORMAT_F32_PM1 = 6, BIFROST_TEXTURE_FORMAT_F32_1 = 7, }; enum bifrost_texture_format_full { /* Transclude bifrost_texture_format from above */ /* Integers, unclamped */ BIFROST_TEXTURE_FORMAT_U16 = 12, BIFROST_TEXTURE_FORMAT_S16 = 13, BIFROST_TEXTURE_FORMAT_U32 = 14, BIFROST_TEXTURE_FORMAT_S32 = 15, }; enum bifrost_texture_fetch { /* Default texelFetch */ BIFROST_TEXTURE_FETCH_TEXEL = 1, /* Deprecated, fetches 4x U32 of a U8 x 4 texture. Do not use. */ BIFROST_TEXTURE_FETCH_GATHER4_RGBA = 3, /* Gathers */ BIFROST_TEXTURE_FETCH_GATHER4_R = 4, BIFROST_TEXTURE_FETCH_GATHER4_G = 5, BIFROST_TEXTURE_FETCH_GATHER4_B = 6, BIFROST_TEXTURE_FETCH_GATHER4_A = 7 }; struct bifrost_texture_operation { /* If immediate_indices is set: * - immediate sampler index * - index used as texture index * Otherwise: * - bifrost_single_index in lower 2 bits * - 0x3 in upper 2 bits (single-texturing) */ unsigned sampler_index_or_mode : 4; unsigned index : 7; bool immediate_indices : 1; enum bifrost_tex_op op : 3; /* If set for TEX/FETCH, loads texel offsets and multisample index from * a staging register containing offset_x:offset_y:offset_z:ms_index * packed 8:8:8:8. Offsets must be in [-31, +31]. If set for * GRDESC(_DER), disable LOD bias. */ bool offset_or_bias_disable : 1; /* If set for TEX/FETCH, loads fp32 shadow comparison value from a * staging register. Implies fetch_component = gather4_r. If set for * GRDESC(_DER), disables LOD clamping. */ bool shadow_or_clamp_disable : 1; /* If set, loads an uint32 array index from a staging register. */ bool array : 1; /* Texture dimension, or 0 for a cubemap */ unsigned dimension : 2; /* Method to compute LOD value or for a FETCH, the * bifrost_texture_fetch component specification */ enum bifrost_lod_mode lod_or_fetch : 3; /* Reserved */ unsigned zero : 1; /* Register format for the result */ enum bifrost_texture_format_full format : 4; /* Write mask for the result */ unsigned mask : 4; } __attribute__((packed)); struct bifrost_dual_texture_operation { unsigned primary_sampler_index : 2; unsigned mode : 2; /* 0x1 for dual */ unsigned primary_texture_index : 2; unsigned secondary_sampler_index : 2; unsigned secondary_texture_index : 2; /* Leave zero for dual texturing */ unsigned reserved : 1; unsigned index_mode_zero : 1; /* Base staging register to write the secondary results to */ unsigned secondary_register : 6; /* Format/mask for each texture */ enum bifrost_texture_format secondary_format : 3; unsigned secondary_mask : 4; enum bifrost_texture_format primary_format : 3; unsigned primary_mask : 4; } __attribute__((packed)); static inline uint32_t bi_dual_tex_as_u32(struct bifrost_dual_texture_operation desc) { uint32_t desc_u; memcpy(&desc_u, &desc, sizeof(desc)); return desc_u; } #define BIFROST_MEGA_SAMPLE 128 #define BIFROST_ALL_SAMPLES 255 #define BIFROST_CURRENT_PIXEL 255 struct bifrost_pixel_indices { unsigned sample : 8; unsigned rt : 8; unsigned x : 8; unsigned y : 8; } __attribute__((packed)); enum bi_constmod { BI_CONSTMOD_NONE, BI_CONSTMOD_PC_LO, BI_CONSTMOD_PC_HI, BI_CONSTMOD_PC_LO_HI }; struct bi_constants { /* Raw constant values */ uint64_t raw[6]; /* Associated modifier derived from M values */ enum bi_constmod mods[6]; }; /* FAU selectors for constants are out-of-order, construct the top bits * here given a embedded constant index in a clause */ static inline unsigned bi_constant_field(unsigned idx) { const unsigned values[] = {4, 5, 6, 7, 2, 3}; assert(idx <= 5); return values[idx] << 4; } #ifdef __cplusplus } /* extern C */ #endif #endif