i965: Avoid validation error when src1 is not present

[mesa.git] / src / intel / compiler / brw_eu_validate.c

/*
 * Copyright © 2015 Intel Corporation
 *
 * 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.
 */

/** @file brw_eu_validate.c
 *
 * This file implements a pass that validates shader assembly.
 */

#include "brw_eu.h"

/* We're going to do lots of string concatenation, so this should help. */
struct string {
   char *str;
   size_t len;
};

static void
cat(struct string *dest, const struct string src)
{
   dest->str = realloc(dest->str, dest->len + src.len + 1);
   memcpy(dest->str + dest->len, src.str, src.len);
   dest->str[dest->len + src.len] = '\0';
   dest->len = dest->len + src.len;
}
#define CAT(dest, src) cat(&dest, (struct string){src, strlen(src)})

#define error(str)   "\tERROR: " str "\n"
#define ERROR_INDENT "\t       "

#define ERROR(msg) ERROR_IF(true, msg)
#define ERROR_IF(cond, msg)          \
   do {                              \
      if (cond) {                    \
         CAT(error_msg, error(msg)); \
      }                              \
   } while(0)

#define CHECK(func, args...)                             \
   do {                                                  \
      struct string __msg = func(devinfo, inst, ##args); \
      if (__msg.str) {                                   \
         cat(&error_msg, __msg);                         \
         free(__msg.str);                                \
      }                                                  \
   } while (0)

#define STRIDE(stride) (stride != 0 ? 1 << ((stride) - 1) : 0)
#define WIDTH(width)   (1 << (width))

static bool
inst_is_send(const struct gen_device_info *devinfo, const brw_inst *inst)
{
   switch (brw_inst_opcode(devinfo, inst)) {
   case BRW_OPCODE_SEND:
   case BRW_OPCODE_SENDC:
   case BRW_OPCODE_SENDS:
   case BRW_OPCODE_SENDSC:
      return true;
   default:
      return false;
   }
}

static unsigned
signed_type(unsigned type)
{
   switch (type) {
   case BRW_REGISTER_TYPE_UD: return BRW_REGISTER_TYPE_D;
   case BRW_REGISTER_TYPE_UW: return BRW_REGISTER_TYPE_W;
   case BRW_REGISTER_TYPE_UB: return BRW_REGISTER_TYPE_B;
   case BRW_REGISTER_TYPE_UQ: return BRW_REGISTER_TYPE_Q;
   default:                   return type;
   }
}

static bool
inst_is_raw_move(const struct gen_device_info *devinfo, const brw_inst *inst)
{
   unsigned dst_type = signed_type(brw_inst_dst_type(devinfo, inst));
   unsigned src_type = signed_type(brw_inst_src0_type(devinfo, inst));

   if (brw_inst_src0_reg_file(devinfo, inst) == BRW_IMMEDIATE_VALUE) {
      /* FIXME: not strictly true */
      if (brw_inst_src0_type(devinfo, inst) == BRW_REGISTER_TYPE_VF ||
          brw_inst_src0_type(devinfo, inst) == BRW_REGISTER_TYPE_UV ||
          brw_inst_src0_type(devinfo, inst) == BRW_REGISTER_TYPE_V) {
         return false;
      }
   } else if (brw_inst_src0_negate(devinfo, inst) ||
              brw_inst_src0_abs(devinfo, inst)) {
      return false;
   }

   return brw_inst_opcode(devinfo, inst) == BRW_OPCODE_MOV &&
          brw_inst_saturate(devinfo, inst) == 0 &&
          dst_type == src_type;
}

static bool
dst_is_null(const struct gen_device_info *devinfo, const brw_inst *inst)
{
   return brw_inst_dst_reg_file(devinfo, inst) == BRW_ARCHITECTURE_REGISTER_FILE &&
          brw_inst_dst_da_reg_nr(devinfo, inst) == BRW_ARF_NULL;
}

static bool
src0_is_null(const struct gen_device_info *devinfo, const brw_inst *inst)
{
   return brw_inst_src0_reg_file(devinfo, inst) == BRW_ARCHITECTURE_REGISTER_FILE &&
          brw_inst_src0_da_reg_nr(devinfo, inst) == BRW_ARF_NULL;
}

static bool
src1_is_null(const struct gen_device_info *devinfo, const brw_inst *inst)
{
   return brw_inst_src1_reg_file(devinfo, inst) == BRW_ARCHITECTURE_REGISTER_FILE &&
          brw_inst_src1_da_reg_nr(devinfo, inst) == BRW_ARF_NULL;
}

static bool
src0_is_grf(const struct gen_device_info *devinfo, const brw_inst *inst)
{
   return brw_inst_src0_reg_file(devinfo, inst) == BRW_GENERAL_REGISTER_FILE;
}

static bool
src0_has_scalar_region(const struct gen_device_info *devinfo, const brw_inst *inst)
{
   return brw_inst_src0_vstride(devinfo, inst) == BRW_VERTICAL_STRIDE_0 &&
          brw_inst_src0_width(devinfo, inst) == BRW_WIDTH_1 &&
          brw_inst_src0_hstride(devinfo, inst) == BRW_HORIZONTAL_STRIDE_0;
}

static bool
src1_has_scalar_region(const struct gen_device_info *devinfo, const brw_inst *inst)
{
   return brw_inst_src1_vstride(devinfo, inst) == BRW_VERTICAL_STRIDE_0 &&
          brw_inst_src1_width(devinfo, inst) == BRW_WIDTH_1 &&
          brw_inst_src1_hstride(devinfo, inst) == BRW_HORIZONTAL_STRIDE_0;
}

static unsigned
num_sources_from_inst(const struct gen_device_info *devinfo,
                      const brw_inst *inst)
{
   const struct opcode_desc *desc =
      brw_opcode_desc(devinfo, brw_inst_opcode(devinfo, inst));
   unsigned math_function;

   if (brw_inst_opcode(devinfo, inst) == BRW_OPCODE_MATH) {
      math_function = brw_inst_math_function(devinfo, inst);
   } else if (devinfo->gen < 6 &&
              brw_inst_opcode(devinfo, inst) == BRW_OPCODE_SEND) {
      if (brw_inst_sfid(devinfo, inst) == BRW_SFID_MATH) {
         /* src1 must be a descriptor (including the information to determine
          * that the SEND is doing an extended math operation), but src0 can
          * actually be null since it serves as the source of the implicit GRF
          * to MRF move.
          *
          * If we stop using that functionality, we'll have to revisit this.
          */
         return 2;
      } else {
         /* Send instructions are allowed to have null sources since they use
          * the base_mrf field to specify which message register source.
          */
         return 0;
      }
   } else {
      assert(desc->nsrc < 4);
      return desc->nsrc;
   }

   switch (math_function) {
   case BRW_MATH_FUNCTION_INV:
   case BRW_MATH_FUNCTION_LOG:
   case BRW_MATH_FUNCTION_EXP:
   case BRW_MATH_FUNCTION_SQRT:
   case BRW_MATH_FUNCTION_RSQ:
   case BRW_MATH_FUNCTION_SIN:
   case BRW_MATH_FUNCTION_COS:
   case BRW_MATH_FUNCTION_SINCOS:
   case GEN8_MATH_FUNCTION_INVM:
   case GEN8_MATH_FUNCTION_RSQRTM:
      return 1;
   case BRW_MATH_FUNCTION_FDIV:
   case BRW_MATH_FUNCTION_POW:
   case BRW_MATH_FUNCTION_INT_DIV_QUOTIENT_AND_REMAINDER:
   case BRW_MATH_FUNCTION_INT_DIV_QUOTIENT:
   case BRW_MATH_FUNCTION_INT_DIV_REMAINDER:
      return 2;
   default:
      unreachable("not reached");
   }
}

static struct string
sources_not_null(const struct gen_device_info *devinfo,
                 const brw_inst *inst)
{
   unsigned num_sources = num_sources_from_inst(devinfo, inst);
   struct string error_msg = { .str = NULL, .len = 0 };

   /* Nothing to test. 3-src instructions can only have GRF sources, and
    * there's no bit to control the file.
    */
   if (num_sources == 3)
      return (struct string){};

   if (num_sources >= 1)
      ERROR_IF(src0_is_null(devinfo, inst), "src0 is null");

   if (num_sources == 2)
      ERROR_IF(src1_is_null(devinfo, inst), "src1 is null");

   return error_msg;
}

static struct string
send_restrictions(const struct gen_device_info *devinfo,
                  const brw_inst *inst)
{
   struct string error_msg = { .str = NULL, .len = 0 };

   if (brw_inst_opcode(devinfo, inst) == BRW_OPCODE_SEND) {
      ERROR_IF(brw_inst_src0_address_mode(devinfo, inst) != BRW_ADDRESS_DIRECT,
               "send must use direct addressing");

      if (devinfo->gen >= 7) {
         ERROR_IF(!src0_is_grf(devinfo, inst), "send from non-GRF");
         ERROR_IF(brw_inst_eot(devinfo, inst) &&
                  brw_inst_src0_da_reg_nr(devinfo, inst) < 112,
                  "send with EOT must use g112-g127");
      }
   }

   return error_msg;
}

static bool
is_unsupported_inst(const struct gen_device_info *devinfo,
                    const brw_inst *inst)
{
   return brw_opcode_desc(devinfo, brw_inst_opcode(devinfo, inst)) == NULL;
}

static enum brw_reg_type
execution_type_for_type(enum brw_reg_type type)
{
   switch (type) {
   case BRW_REGISTER_TYPE_DF:
   case BRW_REGISTER_TYPE_F:
   case BRW_REGISTER_TYPE_HF:
      return type;

   case BRW_REGISTER_TYPE_VF:
      return BRW_REGISTER_TYPE_F;

   case BRW_REGISTER_TYPE_Q:
   case BRW_REGISTER_TYPE_UQ:
      return BRW_REGISTER_TYPE_Q;

   case BRW_REGISTER_TYPE_D:
   case BRW_REGISTER_TYPE_UD:
      return BRW_REGISTER_TYPE_D;

   case BRW_REGISTER_TYPE_W:
   case BRW_REGISTER_TYPE_UW:
   case BRW_REGISTER_TYPE_B:
   case BRW_REGISTER_TYPE_UB:
   case BRW_REGISTER_TYPE_V:
   case BRW_REGISTER_TYPE_UV:
      return BRW_REGISTER_TYPE_W;
   }
   unreachable("not reached");
}

/**
 * Returns the execution type of an instruction \p inst
 */
static enum brw_reg_type
execution_type(const struct gen_device_info *devinfo, const brw_inst *inst)
{
   unsigned num_sources = num_sources_from_inst(devinfo, inst);
   enum brw_reg_type src0_exec_type, src1_exec_type;

   /* Execution data type is independent of destination data type, except in
    * mixed F/HF instructions on CHV and SKL+.
    */
   enum brw_reg_type dst_exec_type = brw_inst_dst_type(devinfo, inst);

   src0_exec_type = execution_type_for_type(brw_inst_src0_type(devinfo, inst));
   if (num_sources == 1) {
      if ((devinfo->gen >= 9 || devinfo->is_cherryview) &&
          src0_exec_type == BRW_REGISTER_TYPE_HF) {
         return dst_exec_type;
      }
      return src0_exec_type;
   }

   src1_exec_type = execution_type_for_type(brw_inst_src1_type(devinfo, inst));
   if (src0_exec_type == src1_exec_type)
      return src0_exec_type;

   /* Mixed operand types where one is float is float on Gen < 6
    * (and not allowed on later platforms)
    */
   if (devinfo->gen < 6 &&
       (src0_exec_type == BRW_REGISTER_TYPE_F ||
        src1_exec_type == BRW_REGISTER_TYPE_F))
      return BRW_REGISTER_TYPE_F;

   if (src0_exec_type == BRW_REGISTER_TYPE_Q ||
       src1_exec_type == BRW_REGISTER_TYPE_Q)
      return BRW_REGISTER_TYPE_Q;

   if (src0_exec_type == BRW_REGISTER_TYPE_D ||
       src1_exec_type == BRW_REGISTER_TYPE_D)
      return BRW_REGISTER_TYPE_D;

   if (src0_exec_type == BRW_REGISTER_TYPE_W ||
       src1_exec_type == BRW_REGISTER_TYPE_W)
      return BRW_REGISTER_TYPE_W;

   if (src0_exec_type == BRW_REGISTER_TYPE_DF ||
       src1_exec_type == BRW_REGISTER_TYPE_DF)
      return BRW_REGISTER_TYPE_DF;

   if (devinfo->gen >= 9 || devinfo->is_cherryview) {
      if (dst_exec_type == BRW_REGISTER_TYPE_F ||
          src0_exec_type == BRW_REGISTER_TYPE_F ||
          src1_exec_type == BRW_REGISTER_TYPE_F) {
         return BRW_REGISTER_TYPE_F;
      } else {
         return BRW_REGISTER_TYPE_HF;
      }
   }

   assert(src0_exec_type == BRW_REGISTER_TYPE_F);
   return BRW_REGISTER_TYPE_F;
}

/**
 * Returns whether a region is packed
 *
 * A region is packed if its elements are adjacent in memory, with no
 * intervening space, no overlap, and no replicated values.
 */
static bool
is_packed(unsigned vstride, unsigned width, unsigned hstride)
{
   if (vstride == width) {
      if (vstride == 1) {
         return hstride == 0;
      } else {
         return hstride == 1;
      }
   }

   return false;
}

/**
 * Checks restrictions listed in "General Restrictions Based on Operand Types"
 * in the "Register Region Restrictions" section.
 */
static struct string
general_restrictions_based_on_operand_types(const struct gen_device_info *devinfo,
                                            const brw_inst *inst)
{
   const struct opcode_desc *desc =
      brw_opcode_desc(devinfo, brw_inst_opcode(devinfo, inst));
   unsigned num_sources = num_sources_from_inst(devinfo, inst);
   unsigned exec_size = 1 << brw_inst_exec_size(devinfo, inst);
   struct string error_msg = { .str = NULL, .len = 0 };

   if (num_sources == 3)
      return (struct string){};

   if (inst_is_send(devinfo, inst))
      return (struct string){};

   if (exec_size == 1)
      return (struct string){};

   if (desc->ndst == 0)
      return (struct string){};

   /* The PRMs say:
    *
    *    Where n is the largest element size in bytes for any source or
    *    destination operand type, ExecSize * n must be <= 64.
    *
    * But we do not attempt to enforce it, because it is implied by other
    * rules:
    *
    *    - that the destination stride must match the execution data type
    *    - sources may not span more than two adjacent GRF registers
    *    - destination may not span more than two adjacent GRF registers
    *
    * In fact, checking it would weaken testing of the other rules.
    */

   unsigned dst_stride = STRIDE(brw_inst_dst_hstride(devinfo, inst));
   enum brw_reg_type dst_type = brw_inst_dst_type(devinfo, inst);
   bool dst_type_is_byte =
      brw_inst_dst_type(devinfo, inst) == BRW_REGISTER_TYPE_B ||
      brw_inst_dst_type(devinfo, inst) == BRW_REGISTER_TYPE_UB;

   if (dst_type_is_byte) {
      if (is_packed(exec_size * dst_stride, exec_size, dst_stride)) {
         if (!inst_is_raw_move(devinfo, inst)) {
            ERROR("Only raw MOV supports a packed-byte destination");
            return error_msg;
         } else {
            return (struct string){};
         }
      }
   }

   unsigned exec_type = execution_type(devinfo, inst);
   unsigned exec_type_size = brw_reg_type_to_size(exec_type);
   unsigned dst_type_size = brw_reg_type_to_size(dst_type);

   /* On IVB/BYT, region parameters and execution size for DF are in terms of
    * 32-bit elements, so they are doubled. For evaluating the validity of an
    * instruction, we halve them.
    */
   if (devinfo->gen == 7 && !devinfo->is_haswell &&
       exec_type_size == 8 && dst_type_size == 4)
      dst_type_size = 8;

   if (exec_type_size > dst_type_size) {
      ERROR_IF(dst_stride * dst_type_size != exec_type_size,
               "Destination stride must be equal to the ratio of the sizes of "
               "the execution data type to the destination type");

      unsigned subreg = brw_inst_dst_da1_subreg_nr(devinfo, inst);

      if (brw_inst_access_mode(devinfo, inst) == BRW_ALIGN_1 &&
          brw_inst_dst_address_mode(devinfo, inst) == BRW_ADDRESS_DIRECT) {
         /* The i965 PRM says:
          *
          *    Implementation Restriction: The relaxed alignment rule for byte
          *    destination (#10.5) is not supported.
          */
         if ((devinfo->gen > 4 || devinfo->is_g4x) && dst_type_is_byte) {
            ERROR_IF(subreg % exec_type_size != 0 &&
                     subreg % exec_type_size != 1,
                     "Destination subreg must be aligned to the size of the "
                     "execution data type (or to the next lowest byte for byte "
                     "destinations)");
         } else {
            ERROR_IF(subreg % exec_type_size != 0,
                     "Destination subreg must be aligned to the size of the "
                     "execution data type");
         }
      }
   }

   return error_msg;
}

/**
 * Checks restrictions listed in "General Restrictions on Regioning Parameters"
 * in the "Register Region Restrictions" section.
 */
static struct string
general_restrictions_on_region_parameters(const struct gen_device_info *devinfo,
                                          const brw_inst *inst)
{
   const struct opcode_desc *desc =
      brw_opcode_desc(devinfo, brw_inst_opcode(devinfo, inst));
   unsigned num_sources = num_sources_from_inst(devinfo, inst);
   unsigned exec_size = 1 << brw_inst_exec_size(devinfo, inst);
   struct string error_msg = { .str = NULL, .len = 0 };

   if (num_sources == 3)
      return (struct string){};

   if (brw_inst_access_mode(devinfo, inst) == BRW_ALIGN_16) {
      if (desc->ndst != 0 && !dst_is_null(devinfo, inst))
         ERROR_IF(brw_inst_dst_hstride(devinfo, inst) != BRW_HORIZONTAL_STRIDE_1,
                  "Destination Horizontal Stride must be 1");

      if (num_sources >= 1) {
         if (devinfo->is_haswell || devinfo->gen >= 8) {
            ERROR_IF(brw_inst_src0_reg_file(devinfo, inst) != BRW_IMMEDIATE_VALUE &&
                     brw_inst_src0_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_0 &&
                     brw_inst_src0_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_2 &&
                     brw_inst_src0_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_4,
                     "In Align16 mode, only VertStride of 0, 2, or 4 is allowed");
         } else {
            ERROR_IF(brw_inst_src0_reg_file(devinfo, inst) != BRW_IMMEDIATE_VALUE &&
                     brw_inst_src0_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_0 &&
                     brw_inst_src0_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_4,
                     "In Align16 mode, only VertStride of 0 or 4 is allowed");
         }
      }

      if (num_sources == 2) {
         if (devinfo->is_haswell || devinfo->gen >= 8) {
            ERROR_IF(brw_inst_src1_reg_file(devinfo, inst) != BRW_IMMEDIATE_VALUE &&
                     brw_inst_src1_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_0 &&
                     brw_inst_src1_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_2 &&
                     brw_inst_src1_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_4,
                     "In Align16 mode, only VertStride of 0, 2, or 4 is allowed");
         } else {
            ERROR_IF(brw_inst_src1_reg_file(devinfo, inst) != BRW_IMMEDIATE_VALUE &&
                     brw_inst_src1_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_0 &&
                     brw_inst_src1_vstride(devinfo, inst) != BRW_VERTICAL_STRIDE_4,
                     "In Align16 mode, only VertStride of 0 or 4 is allowed");
         }
      }

      return error_msg;
   }

   for (unsigned i = 0; i < num_sources; i++) {
      unsigned vstride, width, hstride, element_size, subreg;
      enum brw_reg_type type;

#define DO_SRC(n)                                                              \
      if (brw_inst_src ## n ## _reg_file(devinfo, inst) ==                     \
          BRW_IMMEDIATE_VALUE)                                                 \
         continue;                                                             \
                                                                               \
      vstride = STRIDE(brw_inst_src ## n ## _vstride(devinfo, inst));          \
      width = WIDTH(brw_inst_src ## n ## _width(devinfo, inst));               \
      hstride = STRIDE(brw_inst_src ## n ## _hstride(devinfo, inst));          \
      type = brw_inst_src ## n ## _type(devinfo, inst);                        \
      element_size = brw_reg_type_to_size(type);                               \
      subreg = brw_inst_src ## n ## _da1_subreg_nr(devinfo, inst)

      if (i == 0) {
         DO_SRC(0);
      } else {
         DO_SRC(1);
      }
#undef DO_SRC

      /* On IVB/BYT, region parameters and execution size for DF are in terms of
       * 32-bit elements, so they are doubled. For evaluating the validity of an
       * instruction, we halve them.
       */
      if (devinfo->gen == 7 && !devinfo->is_haswell &&
          element_size == 8)
         element_size = 4;

      /* ExecSize must be greater than or equal to Width. */
      ERROR_IF(exec_size < width, "ExecSize must be greater than or equal "
                                  "to Width");

      /* If ExecSize = Width and HorzStride ≠ 0,
       * VertStride must be set to Width * HorzStride.
       */
      if (exec_size == width && hstride != 0) {
         ERROR_IF(vstride != width * hstride,
                  "If ExecSize = Width and HorzStride ≠ 0, "
                  "VertStride must be set to Width * HorzStride");
      }

      /* If Width = 1, HorzStride must be 0 regardless of the values of
       * ExecSize and VertStride.
       */
      if (width == 1) {
         ERROR_IF(hstride != 0,
                  "If Width = 1, HorzStride must be 0 regardless "
                  "of the values of ExecSize and VertStride");
      }

      /* If ExecSize = Width = 1, both VertStride and HorzStride must be 0. */
      if (exec_size == 1 && width == 1) {
         ERROR_IF(vstride != 0 || hstride != 0,
                  "If ExecSize = Width = 1, both VertStride "
                  "and HorzStride must be 0");
      }

      /* If VertStride = HorzStride = 0, Width must be 1 regardless of the
       * value of ExecSize.
       */
      if (vstride == 0 && hstride == 0) {
         ERROR_IF(width != 1,
                  "If VertStride = HorzStride = 0, Width must be "
                  "1 regardless of the value of ExecSize");
      }

      /* VertStride must be used to cross GRF register boundaries. This rule
       * implies that elements within a 'Width' cannot cross GRF boundaries.
       */
      const uint64_t mask = (1ULL << element_size) - 1;
      unsigned rowbase = subreg;

      for (int y = 0; y < exec_size / width; y++) {
         uint64_t access_mask = 0;
         unsigned offset = rowbase;

         for (int x = 0; x < width; x++) {
            access_mask |= mask << offset;
            offset += hstride * element_size;
         }

         rowbase += vstride * element_size;

         if ((uint32_t)access_mask != 0 && (access_mask >> 32) != 0) {
            ERROR("VertStride must be used to cross GRF register boundaries");
            break;
         }
      }
   }

   /* Dst.HorzStride must not be 0. */
   if (desc->ndst != 0 && !dst_is_null(devinfo, inst)) {
      ERROR_IF(brw_inst_dst_hstride(devinfo, inst) == BRW_HORIZONTAL_STRIDE_0,
               "Destination Horizontal Stride must not be 0");
   }

   return error_msg;
}

/**
 * Creates an \p access_mask for an \p exec_size, \p element_size, and a region
 *
 * An \p access_mask is a 32-element array of uint64_t, where each uint64_t is
 * a bitmask of bytes accessed by the region.
 *
 * For instance the access mask of the source gX.1<4,2,2>F in an exec_size = 4
 * instruction would be
 *
 *    access_mask[0] = 0x00000000000000F0
 *    access_mask[1] = 0x000000000000F000
 *    access_mask[2] = 0x0000000000F00000
 *    access_mask[3] = 0x00000000F0000000
 *    access_mask[4-31] = 0
 *
 * because the first execution channel accesses bytes 7-4 and the second
 * execution channel accesses bytes 15-12, etc.
 */
static void
align1_access_mask(uint64_t access_mask[static 32],
                   unsigned exec_size, unsigned element_size, unsigned subreg,
                   unsigned vstride, unsigned width, unsigned hstride)
{
   const uint64_t mask = (1ULL << element_size) - 1;
   unsigned rowbase = subreg;
   unsigned element = 0;

   for (int y = 0; y < exec_size / width; y++) {
      unsigned offset = rowbase;

      for (int x = 0; x < width; x++) {
         access_mask[element++] = mask << offset;
         offset += hstride * element_size;
      }

      rowbase += vstride * element_size;
   }

   assert(element == 0 || element == exec_size);
}

/**
 * Returns the number of registers accessed according to the \p access_mask
 */
static int
registers_read(const uint64_t access_mask[static 32])
{
   int regs_read = 0;

   for (unsigned i = 0; i < 32; i++) {
      if (access_mask[i] > 0xFFFFFFFF) {
         return 2;
      } else if (access_mask[i]) {
         regs_read = 1;
      }
   }

   return regs_read;
}

/**
 * Checks restrictions listed in "Region Alignment Rules" in the "Register
 * Region Restrictions" section.
 */
static struct string
region_alignment_rules(const struct gen_device_info *devinfo,
                       const brw_inst *inst)
{
   const struct opcode_desc *desc =
      brw_opcode_desc(devinfo, brw_inst_opcode(devinfo, inst));
   unsigned num_sources = num_sources_from_inst(devinfo, inst);
   unsigned exec_size = 1 << brw_inst_exec_size(devinfo, inst);
   uint64_t dst_access_mask[32], src0_access_mask[32], src1_access_mask[32];
   struct string error_msg = { .str = NULL, .len = 0 };

   if (num_sources == 3)
      return (struct string){};

   if (brw_inst_access_mode(devinfo, inst) == BRW_ALIGN_16)
      return (struct string){};

   if (inst_is_send(devinfo, inst))
      return (struct string){};

   memset(dst_access_mask, 0, sizeof(dst_access_mask));
   memset(src0_access_mask, 0, sizeof(src0_access_mask));
   memset(src1_access_mask, 0, sizeof(src1_access_mask));

   for (unsigned i = 0; i < num_sources; i++) {
      unsigned vstride, width, hstride, element_size, subreg;
      enum brw_reg_type type;

      /* In Direct Addressing mode, a source cannot span more than 2 adjacent
       * GRF registers.
       */

#define DO_SRC(n)                                                              \
      if (brw_inst_src ## n ## _address_mode(devinfo, inst) !=                 \
          BRW_ADDRESS_DIRECT)                                                  \
         continue;                                                             \
                                                                               \
      if (brw_inst_src ## n ## _reg_file(devinfo, inst) ==                     \
          BRW_IMMEDIATE_VALUE)                                                 \
         continue;                                                             \
                                                                               \
      vstride = STRIDE(brw_inst_src ## n ## _vstride(devinfo, inst));          \
      width = WIDTH(brw_inst_src ## n ## _width(devinfo, inst));               \
      hstride = STRIDE(brw_inst_src ## n ## _hstride(devinfo, inst));          \
      type = brw_inst_src ## n ## _type(devinfo, inst);                        \
      element_size = brw_reg_type_to_size(type);                               \
      subreg = brw_inst_src ## n ## _da1_subreg_nr(devinfo, inst);             \
      align1_access_mask(src ## n ## _access_mask,                             \
                         exec_size, element_size, subreg,                      \
                         vstride, width, hstride)

      if (i == 0) {
         DO_SRC(0);
      } else {
         DO_SRC(1);
      }
#undef DO_SRC

      unsigned num_vstride = exec_size / width;
      unsigned num_hstride = width;
      unsigned vstride_elements = (num_vstride - 1) * vstride;
      unsigned hstride_elements = (num_hstride - 1) * hstride;
      unsigned offset = (vstride_elements + hstride_elements) * element_size +
                        subreg;
      ERROR_IF(offset >= 64,
               "A source cannot span more than 2 adjacent GRF registers");
   }

   if (desc->ndst == 0 || dst_is_null(devinfo, inst))
      return error_msg;

   unsigned stride = STRIDE(brw_inst_dst_hstride(devinfo, inst));
   enum brw_reg_type dst_type = brw_inst_dst_type(devinfo, inst);
   unsigned element_size = brw_reg_type_to_size(dst_type);
   unsigned subreg = brw_inst_dst_da1_subreg_nr(devinfo, inst);
   unsigned offset = ((exec_size - 1) * stride * element_size) + subreg;
   ERROR_IF(offset >= 64,
            "A destination cannot span more than 2 adjacent GRF registers");

   if (error_msg.str)
      return error_msg;

   /* On IVB/BYT, region parameters and execution size for DF are in terms of
    * 32-bit elements, so they are doubled. For evaluating the validity of an
    * instruction, we halve them.
    */
   if (devinfo->gen == 7 && !devinfo->is_haswell &&
       element_size == 8)
      element_size = 4;

   align1_access_mask(dst_access_mask, exec_size, element_size, subreg,
                      exec_size == 1 ? 0 : exec_size * stride,
                      exec_size == 1 ? 1 : exec_size,
                      exec_size == 1 ? 0 : stride);

   unsigned dst_regs = registers_read(dst_access_mask);
   unsigned src0_regs = registers_read(src0_access_mask);
   unsigned src1_regs = registers_read(src1_access_mask);

   /* The SNB, IVB, HSW, BDW, and CHV PRMs say:
    *
    *    When an instruction has a source region spanning two registers and a
    *    destination region contained in one register, the number of elements
    *    must be the same between two sources and one of the following must be
    *    true:
    *
    *       1. The destination region is entirely contained in the lower OWord
    *          of a register.
    *       2. The destination region is entirely contained in the upper OWord
    *          of a register.
    *       3. The destination elements are evenly split between the two OWords
    *          of a register.
    */
   if (devinfo->gen <= 8) {
      if (dst_regs == 1 && (src0_regs == 2 || src1_regs == 2)) {
         unsigned upper_oword_writes = 0, lower_oword_writes = 0;

         for (unsigned i = 0; i < exec_size; i++) {
            if (dst_access_mask[i] > 0x0000FFFF) {
               upper_oword_writes++;
            } else {
               assert(dst_access_mask[i] != 0);
               lower_oword_writes++;
            }
         }

         ERROR_IF(lower_oword_writes != 0 &&
                  upper_oword_writes != 0 &&
                  upper_oword_writes != lower_oword_writes,
                  "Writes must be to only one OWord or "
                  "evenly split between OWords");
      }
   }

   /* The IVB and HSW PRMs say:
    *
    *    When an instruction has a source region that spans two registers and
    *    the destination spans two registers, the destination elements must be
    *    evenly split between the two registers [...]
    *
    * The SNB PRM contains similar wording (but written in a much more
    * confusing manner).
    *
    * The BDW PRM says:
    *
    *    When destination spans two registers, the source may be one or two
    *    registers. The destination elements must be evenly split between the
    *    two registers.
    *
    * The SKL PRM says:
    *
    *    When destination of MATH instruction spans two registers, the
    *    destination elements must be evenly split between the two registers.
    *
    * It is not known whether this restriction applies to KBL other Gens after
    * SKL.
    */
   if (devinfo->gen <= 8 ||
       brw_inst_opcode(devinfo, inst) == BRW_OPCODE_MATH) {

      /* Nothing explicitly states that on Gen < 8 elements must be evenly
       * split between two destination registers in the two exceptional
       * source-region-spans-one-register cases, but since Broadwell requires
       * evenly split writes regardless of source region, we assume that it was
       * an oversight and require it.
       */
      if (dst_regs == 2) {
         unsigned upper_reg_writes = 0, lower_reg_writes = 0;

         for (unsigned i = 0; i < exec_size; i++) {
            if (dst_access_mask[i] > 0xFFFFFFFF) {
               upper_reg_writes++;
            } else {
               assert(dst_access_mask[i] != 0);
               lower_reg_writes++;
            }
         }

         ERROR_IF(upper_reg_writes != lower_reg_writes,
                  "Writes must be evenly split between the two "
                  "destination registers");
      }
   }

   /* The IVB and HSW PRMs say:
    *
    *    When an instruction has a source region that spans two registers and
    *    the destination spans two registers, the destination elements must be
    *    evenly split between the two registers and each destination register
    *    must be entirely derived from one source register.
    *
    *    Note: In such cases, the regioning parameters must ensure that the
    *    offset from the two source registers is the same.
    *
    * The SNB PRM contains similar wording (but written in a much more
    * confusing manner).
    *
    * There are effectively three rules stated here:
    *
    *    For an instruction with a source and a destination spanning two
    *    registers,
    *
    *       (1) destination elements must be evenly split between the two
    *           registers
    *       (2) all destination elements in a register must be derived
    *           from one source register
    *       (3) the offset (i.e. the starting location in each of the two
    *           registers spanned by a region) must be the same in the two
    *           registers spanned by a region
    *
    * It is impossible to violate rule (1) without violating (2) or (3), so we
    * do not attempt to validate it.
    */
   if (devinfo->gen <= 7 && dst_regs == 2) {
      for (unsigned i = 0; i < num_sources; i++) {
#define DO_SRC(n)                                                             \
         if (src ## n ## _regs <= 1)                                          \
            continue;                                                         \
                                                                              \
         for (unsigned i = 0; i < exec_size; i++) {                           \
            if ((dst_access_mask[i] > 0xFFFFFFFF) !=                          \
                (src ## n ## _access_mask[i] > 0xFFFFFFFF)) {                 \
               ERROR("Each destination register must be entirely derived "    \
                     "from one source register");                             \
               break;                                                         \
            }                                                                 \
         }                                                                    \
                                                                              \
         unsigned offset_0 =                                                  \
            brw_inst_src ## n ## _da1_subreg_nr(devinfo, inst);               \
         unsigned offset_1 = offset_0;                                        \
                                                                              \
         for (unsigned i = 0; i < exec_size; i++) {                           \
            if (src ## n ## _access_mask[i] > 0xFFFFFFFF) {                   \
               offset_1 = __builtin_ctzll(src ## n ## _access_mask[i]) - 32;  \
               break;                                                         \
            }                                                                 \
         }                                                                    \
                                                                              \
         ERROR_IF(num_sources == 2 && offset_0 != offset_1,                   \
                  "The offset from the two source registers "                 \
                  "must be the same")

         if (i == 0) {
            DO_SRC(0);
         } else {
            DO_SRC(1);
         }
#undef DO_SRC
      }
   }

   /* The IVB and HSW PRMs say:
    *
    *    When destination spans two registers, the source MUST span two
    *    registers. The exception to the above rule:
    *        1. When source is scalar, the source registers are not
    *           incremented.
    *        2. When source is packed integer Word and destination is packed
    *           integer DWord, the source register is not incremented by the
    *           source sub register is incremented.
    *
    * The SNB PRM does not contain this rule, but the internal documentation
    * indicates that it applies to SNB as well. We assume that the rule applies
    * to Gen <= 5 although their PRMs do not state it.
    *
    * While the documentation explicitly says in exception (2) that the
    * destination must be an integer DWord, the hardware allows at least a
    * float destination type as well. We emit such instructions from
    *
    *    fs_visitor::emit_interpolation_setup_gen6
    *    fs_visitor::emit_fragcoord_interpolation
    *
    * and have for years with no ill effects.
    *
    * Additionally the simulator source code indicates that the real condition
    * is that the size of the destination type is 4 bytes.
    */
   if (devinfo->gen <= 7 && dst_regs == 2) {
      enum brw_reg_type dst_type = brw_inst_dst_type(devinfo, inst);
      bool dst_is_packed_dword =
         is_packed(exec_size * stride, exec_size, stride) &&
         brw_reg_type_to_size(dst_type) == 4;

      for (unsigned i = 0; i < num_sources; i++) {
#define DO_SRC(n)                                                                  \
         unsigned vstride, width, hstride;                                         \
         vstride = STRIDE(brw_inst_src ## n ## _vstride(devinfo, inst));           \
         width = WIDTH(brw_inst_src ## n ## _width(devinfo, inst));                \
         hstride = STRIDE(brw_inst_src ## n ## _hstride(devinfo, inst));           \
         bool src ## n ## _is_packed_word =                                        \
            is_packed(vstride, width, hstride) &&                                  \
            (brw_inst_src ## n ## _type(devinfo, inst) == BRW_REGISTER_TYPE_W ||   \
             brw_inst_src ## n ## _type(devinfo, inst) == BRW_REGISTER_TYPE_UW);   \
                                                                                   \
         ERROR_IF(src ## n ## _regs == 1 &&                                        \
                  !src ## n ## _has_scalar_region(devinfo, inst) &&                \
                  !(dst_is_packed_dword && src ## n ## _is_packed_word),           \
                  "When the destination spans two registers, the source must "     \
                  "span two registers\n" ERROR_INDENT "(exceptions for scalar "    \
                  "source and packed-word to packed-dword expansion)")

         if (i == 0) {
            DO_SRC(0);
         } else {
            DO_SRC(1);
         }
#undef DO_SRC
      }
   }

   return error_msg;
}

static struct string
vector_immediate_restrictions(const struct gen_device_info *devinfo,
                              const brw_inst *inst)
{
   unsigned num_sources = num_sources_from_inst(devinfo, inst);
   struct string error_msg = { .str = NULL, .len = 0 };

   if (num_sources == 3 || num_sources == 0)
      return (struct string){};

   unsigned file = num_sources == 1 ?
                   brw_inst_src0_reg_file(devinfo, inst) :
                   brw_inst_src1_reg_file(devinfo, inst);
   if (file != BRW_IMMEDIATE_VALUE)
      return (struct string){};

   enum brw_reg_type dst_type = brw_inst_dst_type(devinfo, inst);
   unsigned dst_type_size = brw_reg_type_to_size(dst_type);
   unsigned dst_subreg = brw_inst_access_mode(devinfo, inst) == BRW_ALIGN_1 ?
                         brw_inst_dst_da1_subreg_nr(devinfo, inst) : 0;
   unsigned dst_stride = STRIDE(brw_inst_dst_hstride(devinfo, inst));
   enum brw_reg_type type = num_sources == 1 ?
                            brw_inst_src0_type(devinfo, inst) :
                            brw_inst_src1_type(devinfo, inst);

   /* The PRMs say:
    *
    *    When an immediate vector is used in an instruction, the destination
    *    must be 128-bit aligned with destination horizontal stride equivalent
    *    to a word for an immediate integer vector (v) and equivalent to a
    *    DWord for an immediate float vector (vf).
    *
    * The text has not been updated for the addition of the immediate unsigned
    * integer vector type (uv) on SNB, but presumably the same restriction
    * applies.
    */
   switch (type) {
   case BRW_REGISTER_TYPE_V:
   case BRW_REGISTER_TYPE_UV:
   case BRW_REGISTER_TYPE_VF:
      ERROR_IF(dst_subreg % (128 / 8) != 0,
               "Destination must be 128-bit aligned in order to use immediate "
               "vector types");

      if (type == BRW_REGISTER_TYPE_VF) {
         ERROR_IF(dst_type_size * dst_stride != 4,
                  "Destination must have stride equivalent to dword in order "
                  "to use the VF type");
      } else {
         ERROR_IF(dst_type_size * dst_stride != 2,
                  "Destination must have stride equivalent to word in order "
                  "to use the V or UV type");
      }
      break;
   default:
      break;
   }

   return error_msg;
}

bool
brw_validate_instructions(const struct gen_device_info *devinfo,
                          void *assembly, int start_offset, int end_offset,
                          struct annotation_info *annotation)
{
   bool valid = true;

   for (int src_offset = start_offset; src_offset < end_offset;) {
      struct string error_msg = { .str = NULL, .len = 0 };
      const brw_inst *inst = assembly + src_offset;
      bool is_compact = brw_inst_cmpt_control(devinfo, inst);
      brw_inst uncompacted;

      if (is_compact) {
         brw_compact_inst *compacted = (void *)inst;
         brw_uncompact_instruction(devinfo, &uncompacted, compacted);
         inst = &uncompacted;
      }

      if (is_unsupported_inst(devinfo, inst)) {
         ERROR("Instruction not supported on this Gen");
      } else {
         CHECK(sources_not_null);
         CHECK(send_restrictions);
         CHECK(general_restrictions_based_on_operand_types);
         CHECK(general_restrictions_on_region_parameters);
         CHECK(region_alignment_rules);
         CHECK(vector_immediate_restrictions);
      }

      if (error_msg.str && annotation) {
         annotation_insert_error(annotation, src_offset, error_msg.str);
      }
      valid = valid && error_msg.len == 0;
      free(error_msg.str);

      if (is_compact) {
         src_offset += sizeof(brw_compact_inst);
      } else {
         src_offset += sizeof(brw_inst);
      }
   }

   return valid;
}