/*
 * Copyright (C) 2019 Connor Abbott <cwabbott0@gmail.com>
 * Copyright (C) 2019 Lyude Paul <thatslyude@gmail.com>
 * Copyright (C) 2019 Ryan Houdek <Sonicadvance1@gmail.com>
 * SPDX-License-Identifier: MIT
 */

#ifndef __bifrost_h__
#define __bifrost_h__

#include <assert.h>
#include <stdbool.h>
#include <stdint.h>
#include <string.h>

#ifdef __cplusplus
extern "C" {
#endif

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 {
   union {
      struct {
         /* 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 */
         unsigned 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;
      };

      uint32_t packed;
   };
} __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 */
   /* There are at most 6 constants per clause, but internally
    * we can use an extra slot for modifiers, so give room for 7
    */
   uint64_t raw[7];

   /* Associated modifier derived from M values */
   enum bi_constmod mods[7];
};

/* 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
