nir/i965: use two slots from inputs_read for dvec3/dvec4 vertex input attributes

So far, input_reads was a bitmap tracking which vertex input locations
were being used.

In OpenGL, an attribute bigger than a vec4 (like a dvec3 or dvec4)
consumes just one location, any other small attribute. So we mark the
proper bit in inputs_read, and also the same bit in double_inputs_read
if the attribute is a dvec3/dvec4.

But in Vulkan, this is slightly different: a dvec3/dvec4 attribute
consumes two locations, not just one. And hence two bits would be marked
in inputs_read for the same vertex input attribute.

To avoid handling two different situations in NIR, we just choose the
latest one: in OpenGL, when creating NIR from GLSL/IR, any dvec3/dvec4
vertex input attribute is marked with two bits in the inputs_read bitmap
(and also in the double_inputs_read), and following attributes are
adjusted accordingly.

As example, if in our GLSL/IR shader we have three attributes:

layout(location = 0) vec3  attr0;
layout(location = 1) dvec4 attr1;
layout(location = 2) dvec3 attr2;

then in our NIR shader we put attr0 in location 0, attr1 in locations 1
and 2, and attr2 in location 3 and 4.

Checking carefully, basically we are using slots rather than locations
in NIR.

When emitting the vertices, we do a inverse map to know the
corresponding location for each slot.

v2 (Jason):
- use two slots from inputs_read for dvec3/dvec4 NIR from GLSL/IR.

v3 (Jason):
- Fix commit log error.
- Use ladder ifs and fix braces.
- elements_double is divisible by 2, don't need DIV_ROUND_UP().
- Use if ladder instead of a switch.
- Add comment about hardware restriction in 64bit vertex attributes.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/glsl/glsl_to_nir.cpp

@@ -129,6 +129,19 @@ private:
 
 } /* end of anonymous namespace */
 
+static void
+nir_remap_attributes(nir_shader *shader)
+{
+   nir_foreach_variable(var, &shader->inputs) {
+      var->data.location += _mesa_bitcount_64(shader->info->double_inputs_read &
+                                              BITFIELD64_MASK(var->data.location));
+   }
+
+   /* Once the remap is done, reset double_inputs_read, so later it will have
+    * which location/slots are doubles */
+   shader->info->double_inputs_read = 0;
+}
+
 nir_shader *
 glsl_to_nir(const struct gl_shader_program *shader_prog,
             gl_shader_stage stage,
@@ -146,6 +159,13 @@ glsl_to_nir(const struct gl_shader_program *shader_prog,
 
    nir_lower_constant_initializers(shader, (nir_variable_mode)~0);
 
+   /* Remap the locations to slots so those requiring two slots will occupy
+    * two locations. For instance, if we have in the IR code a dvec3 attr0 in
+    * location 0 and vec4 attr1 in location 1, in NIR attr0 will use
+    * locations/slots 0 and 1, and attr1 will use location/slot 2 */
+   if (shader->stage == MESA_SHADER_VERTEX)
+      nir_remap_attributes(shader);
+
    shader->info->name = ralloc_asprintf(shader, "GLSL%d", shader_prog->Name);
    if (shader_prog->Label)
       shader->info->label = ralloc_strdup(shader, shader_prog->Label);
@@ -322,6 +342,14 @@ nir_visitor::visit(ir_variable *ir)
             var->data.compact = ir->type->without_array()->is_scalar();
          }
       }
+
+      /* Mark all the locations that require two slots */
+      if (glsl_type_is_dual_slot(glsl_without_array(var->type))) {
+         for (uint i = 0; i < glsl_count_attribute_slots(var->type, true); i++) {
+            uint64_t bitfield = BITFIELD64_BIT(var->data.location + i);
+            shader->info->double_inputs_read |= bitfield;
+         }
+      }
       break;
 
    case ir_var_shader_out:

src/compiler/nir/nir_gather_info.c

@@ -53,11 +53,6 @@ set_io_mask(nir_shader *shader, nir_variable *var, int offset, int len)
          else
             shader->info->inputs_read |= bitfield;
 
-         /* double inputs read is only for vertex inputs */
-         if (shader->stage == MESA_SHADER_VERTEX &&
-             glsl_type_is_dual_slot(glsl_without_array(var->type)))
-            shader->info->double_inputs_read |= bitfield;
-
          if (shader->stage == MESA_SHADER_FRAGMENT) {
             shader->info->fs.uses_sample_qualifier |= var->data.sample;
          }
@@ -83,26 +78,21 @@ static void
 mark_whole_variable(nir_shader *shader, nir_variable *var)
 {
    const struct glsl_type *type = var->type;
-   bool is_vertex_input = false;
 
    if (nir_is_per_vertex_io(var, shader->stage)) {
       assert(glsl_type_is_array(type));
       type = glsl_get_array_element(type);
    }
 
-   if (shader->stage == MESA_SHADER_VERTEX &&
-       var->data.mode == nir_var_shader_in)
-      is_vertex_input = true;
-
    const unsigned slots =
       var->data.compact ? DIV_ROUND_UP(glsl_get_length(type), 4)
-                        : glsl_count_attribute_slots(type, is_vertex_input);
+                        : glsl_count_attribute_slots(type, false);
 
    set_io_mask(shader, var, 0, slots);
 }
 
 static unsigned
-get_io_offset(nir_deref_var *deref, bool is_vertex_input)
+get_io_offset(nir_deref_var *deref)
 {
    unsigned offset = 0;
 
@@ -117,7 +107,7 @@ get_io_offset(nir_deref_var *deref, bool is_vertex_input)
             return -1;
          }
 
-         offset += glsl_count_attribute_slots(tail->type, is_vertex_input) *
+         offset += glsl_count_attribute_slots(tail->type, false) *
             deref_array->base_offset;
       }
       /* TODO: we can get the offset for structs here see nir_lower_io() */
@@ -163,12 +153,7 @@ try_mask_partial_io(nir_shader *shader, nir_deref_var *deref)
       return false;
    }
 
-   bool is_vertex_input = false;
-   if (shader->stage == MESA_SHADER_VERTEX &&
-       var->data.mode == nir_var_shader_in)
-      is_vertex_input = true;
-
-   unsigned offset = get_io_offset(deref, is_vertex_input);
+   unsigned offset = get_io_offset(deref);
    if (offset == -1)
       return false;
 
@@ -184,8 +169,7 @@ try_mask_partial_io(nir_shader *shader, nir_deref_var *deref)
    }
 
    /* double element width for double types that takes two slots */
-   if (!is_vertex_input &&
-       glsl_type_is_dual_slot(glsl_without_array(type))) {
+   if (glsl_type_is_dual_slot(glsl_without_array(type))) {
       elem_width *= 2;
    }
 
@@ -220,13 +204,27 @@ gather_intrinsic_info(nir_intrinsic_instr *instr, nir_shader *shader)
    case nir_intrinsic_interp_var_at_sample:
    case nir_intrinsic_interp_var_at_offset:
    case nir_intrinsic_load_var:
-   case nir_intrinsic_store_var:
-      if (instr->variables[0]->var->data.mode == nir_var_shader_in ||
-          instr->variables[0]->var->data.mode == nir_var_shader_out) {
+   case nir_intrinsic_store_var: {
+      nir_variable *var = instr->variables[0]->var;
+
+      if (var->data.mode == nir_var_shader_in ||
+          var->data.mode == nir_var_shader_out) {
          if (!try_mask_partial_io(shader, instr->variables[0]))
-            mark_whole_variable(shader, instr->variables[0]->var);
+            mark_whole_variable(shader, var);
+
+         /* We need to track which input_reads bits correspond to a
+          * dvec3/dvec4 input attribute */
+         if (shader->stage == MESA_SHADER_VERTEX &&
+             var->data.mode == nir_var_shader_in &&
+             glsl_type_is_dual_slot(glsl_without_array(var->type))) {
+            for (uint i = 0; i < glsl_count_attribute_slots(var->type, false); i++) {
+               int idx = var->data.location + i;
+               shader->info->double_inputs_read |= BITFIELD64_BIT(idx);
+            }
+         }
       }
       break;
+   }
 
    case nir_intrinsic_load_draw_id:
    case nir_intrinsic_load_front_face:

src/intel/vulkan/genX_pipeline.c

@@ -42,9 +42,35 @@ vertex_element_comp_control(enum isl_format format, unsigned comp)
    default: unreachable("Invalid component");
    }
 
+   /*
+    * Take in account hardware restrictions when dealing with 64-bit floats.
+    *
+    * From Broadwell spec, command reference structures, page 586:
+    *  "When SourceElementFormat is set to one of the *64*_PASSTHRU formats,
+    *   64-bit components are stored * in the URB without any conversion. In
+    *   this case, vertex elements must be written as 128 or 256 bits, with
+    *   VFCOMP_STORE_0 being used to pad the output as required. E.g., if
+    *   R64_PASSTHRU is used to copy a 64-bit Red component into the URB,
+    *   Component 1 must be specified as VFCOMP_STORE_0 (with Components 2,3
+    *   set to VFCOMP_NOSTORE) in order to output a 128-bit vertex element, or
+    *   Components 1-3 must be specified as VFCOMP_STORE_0 in order to output
+    *   a 256-bit vertex element. Likewise, use of R64G64B64_PASSTHRU requires
+    *   Component 3 to be specified as VFCOMP_STORE_0 in order to output a
+    *   256-bit vertex element."
+    */
    if (bits) {
       return VFCOMP_STORE_SRC;
-   } else if (comp < 3) {
+   } else if (comp >= 2 &&
+              !isl_format_layouts[format].channels.b.bits &&
+              isl_format_layouts[format].channels.r.type == ISL_RAW) {
+      /* When emitting 64-bit attributes, we need to write either 128 or 256
+       * bit chunks, using VFCOMP_NOSTORE when not writing the chunk, and
+       * VFCOMP_STORE_0 to pad the written chunk */
+      return VFCOMP_NOSTORE;
+   } else if (comp < 3 ||
+              isl_format_layouts[format].channels.r.type == ISL_RAW) {
+      /* Note we need to pad with value 0, not 1, due hardware restrictions
+       * (see comment above) */
       return VFCOMP_STORE_0;
    } else if (isl_format_layouts[format].channels.r.type == ISL_UINT ||
             isl_format_layouts[format].channels.r.type == ISL_SINT) {
@@ -64,8 +90,10 @@ emit_vertex_input(struct anv_pipeline *pipeline,
 
    /* Pull inputs_read out of the VS prog data */
    const uint64_t inputs_read = vs_prog_data->inputs_read;
+   const uint64_t double_inputs_read = vs_prog_data->double_inputs_read;
    assert((inputs_read & ((1 << VERT_ATTRIB_GENERIC0) - 1)) == 0);
    const uint32_t elements = inputs_read >> VERT_ATTRIB_GENERIC0;
+   const uint32_t elements_double = double_inputs_read >> VERT_ATTRIB_GENERIC0;
 
 #if GEN_GEN >= 8
    /* On BDW+, we only need to allocate space for base ids.  Setting up
@@ -83,13 +111,16 @@ emit_vertex_input(struct anv_pipeline *pipeline,
                                 vs_prog_data->uses_baseinstance;
 #endif
 
-   uint32_t elem_count = __builtin_popcount(elements) + needs_svgs_elem;
-   if (elem_count == 0)
+   uint32_t elem_count = __builtin_popcount(elements) -
+      __builtin_popcount(elements_double) / 2;
+
+   uint32_t total_elems = elem_count + needs_svgs_elem;
+   if (total_elems == 0)
       return;
 
    uint32_t *p;
 
-   const uint32_t num_dwords = 1 + elem_count * 2;
+   const uint32_t num_dwords = 1 + total_elems * 2;
    p = anv_batch_emitn(&pipeline->batch, num_dwords,
                        GENX(3DSTATE_VERTEX_ELEMENTS));
    memset(p + 1, 0, (num_dwords - 1) * 4);
@@ -107,7 +138,10 @@ emit_vertex_input(struct anv_pipeline *pipeline,
       if ((elements & (1 << desc->location)) == 0)
          continue; /* Binding unused */
 
-      uint32_t slot = __builtin_popcount(elements & ((1 << desc->location) - 1));
+      uint32_t slot =
+         __builtin_popcount(elements & ((1 << desc->location) - 1)) -
+         DIV_ROUND_UP(__builtin_popcount(elements_double &
+                                        ((1 << desc->location) -1)), 2);
 
       struct GENX(VERTEX_ELEMENT_STATE) element = {
          .VertexBufferIndex = desc->binding,
@@ -137,7 +171,7 @@ emit_vertex_input(struct anv_pipeline *pipeline,
 #endif
    }
 
-   const uint32_t id_slot = __builtin_popcount(elements);
+   const uint32_t id_slot = elem_count;
    if (needs_svgs_elem) {
       /* From the Broadwell PRM for the 3D_Vertex_Component_Control enum:
        *    "Within a VERTEX_ELEMENT_STATE structure, if a Component

src/mesa/drivers/dri/i965/brw_draw_upload.c

@@ -481,11 +481,16 @@ brw_prepare_vertices(struct brw_context *brw)
    /* Accumulate the list of enabled arrays. */
    brw->vb.nr_enabled = 0;
    while (vs_inputs) {
-      GLuint index = ffsll(vs_inputs) - 1;
+      GLuint first = ffsll(vs_inputs) - 1;
+      GLuint index =
+         first - DIV_ROUND_UP(_mesa_bitcount_64(vs_prog_data->double_inputs_read &
+                                                BITFIELD64_MASK(first)), 2);
       struct brw_vertex_element *input = &brw->vb.inputs[index];
       input->is_dual_slot = brw->gen >= 8 &&
-         (vs_prog_data->double_inputs_read & BITFIELD64_BIT(index)) != 0;
-      vs_inputs &= ~BITFIELD64_BIT(index);
+         (vs_prog_data->double_inputs_read & BITFIELD64_BIT(first)) != 0;
+      vs_inputs &= ~BITFIELD64_BIT(first);
+      if (input->is_dual_slot)
+         vs_inputs &= ~BITFIELD64_BIT(first + 1);
       brw->vb.enabled[brw->vb.nr_enabled++] = input;
    }
 

src/mesa/drivers/dri/i965/brw_fs.cpp

@@ -492,19 +492,6 @@ type_size_scalar(const struct glsl_type *type)
    return 0;
 }
 
-/* Attribute arrays are loaded as one vec4 per element (or matrix column),
- * except for double-precision types, which are loaded as one dvec4.
- */
-extern "C" int
-type_size_vs_input(const struct glsl_type *type)
-{
-   if (type->is_double()) {
-      return type_size_dvec4(type);
-   } else {
-      return type_size_vec4(type);
-   }
-}
-
 /**
  * Create a MOV to read the timestamp register.
  *

src/mesa/drivers/dri/i965/brw_fs_visitor.cpp

@@ -36,8 +36,7 @@ fs_reg *
 fs_visitor::emit_vs_system_value(int location)
 {
    fs_reg *reg = new(this->mem_ctx)
-      fs_reg(ATTR, 4 * (_mesa_bitcount_64(nir->info->inputs_read) +
-                        _mesa_bitcount_64(nir->info->double_inputs_read)),
+      fs_reg(ATTR, 4 * _mesa_bitcount_64(nir->info->inputs_read),
              BRW_REGISTER_TYPE_D);
    struct brw_vs_prog_data *vs_prog_data = brw_vs_prog_data(prog_data);
 

src/mesa/drivers/dri/i965/brw_nir.c

@@ -113,9 +113,7 @@ remap_vs_attrs(nir_block *block, shader_info *nir_info)
          int attr = intrin->const_index[0];
          int slot = _mesa_bitcount_64(nir_info->inputs_read &
                                       BITFIELD64_MASK(attr));
-         int dslot = _mesa_bitcount_64(nir_info->double_inputs_read &
-                                       BITFIELD64_MASK(attr));
-         intrin->const_index[0] = 4 * (slot + dslot);
+         intrin->const_index[0] = 4 * slot;
       }
    }
    return true;
@@ -268,7 +266,7 @@ brw_nir_lower_vs_inputs(nir_shader *nir,
     * loaded as one vec4 or dvec4 per element (or matrix column), depending on
     * whether it is a double-precision type or not.
     */
-   nir_lower_io(nir, nir_var_shader_in, type_size_vs_input, 0);
+   nir_lower_io(nir, nir_var_shader_in, type_size_vec4, 0);
 
    /* This pass needs actual constants */
    nir_opt_constant_folding(nir);

src/mesa/drivers/dri/i965/brw_nir.h

@@ -34,7 +34,6 @@ extern "C" {
 int type_size_scalar(const struct glsl_type *type);
 int type_size_vec4(const struct glsl_type *type);
 int type_size_dvec4(const struct glsl_type *type);
-int type_size_vs_input(const struct glsl_type *type);
 
 static inline int
 type_size_scalar_bytes(const struct glsl_type *type)

src/mesa/drivers/dri/i965/brw_vec4.cpp

@@ -2737,7 +2737,7 @@ brw_compile_vs(const struct brw_compiler *compiler, void *log_data,
       ((1 << shader->info->cull_distance_array_size) - 1) <<
       shader->info->clip_distance_array_size;
 
-   unsigned nr_attributes = _mesa_bitcount_64(prog_data->inputs_read);
+   unsigned nr_attribute_slots = _mesa_bitcount_64(prog_data->inputs_read);
 
    /* gl_VertexID and gl_InstanceID are system values, but arrive via an
     * incoming vertex attribute.  So, add an extra slot.
@@ -2747,18 +2747,17 @@ brw_compile_vs(const struct brw_compiler *compiler, void *log_data,
         BITFIELD64_BIT(SYSTEM_VALUE_BASE_INSTANCE) |
         BITFIELD64_BIT(SYSTEM_VALUE_VERTEX_ID_ZERO_BASE) |
         BITFIELD64_BIT(SYSTEM_VALUE_INSTANCE_ID))) {
-      nr_attributes++;
+      nr_attribute_slots++;
    }
 
    /* gl_DrawID has its very own vec4 */
    if (shader->info->system_values_read &
        BITFIELD64_BIT(SYSTEM_VALUE_DRAW_ID)) {
-      nr_attributes++;
+      nr_attribute_slots++;
    }
 
-   unsigned nr_attribute_slots =
-      nr_attributes +
-      _mesa_bitcount_64(shader->info->double_inputs_read);
+   unsigned nr_attributes = nr_attribute_slots -
+      DIV_ROUND_UP(_mesa_bitcount_64(shader->info->double_inputs_read), 2);
 
    /* The 3DSTATE_VS documentation lists the lower bound on "Vertex URB Entry
     * Read Length" as 1 in vec4 mode, and 0 in SIMD8 mode.  Empirically, in