Mesa (master): glsl: fix overlapping of varying locations for arrays and structs

[Timothy Arceri]

Module: Mesa
Branch: master
Commit: ac6e2c2056469226fdeefb96bee632546f45a0fb
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=ac6e2c2056469226fdeefb96bee632546f45a0fb

Author: Timothy Arceri <timothy.arceri at collabora.com>
Date:   Tue Dec 15 16:40:26 2015 +1100

glsl: fix overlapping of varying locations for arrays and structs

Previously we were only reserving a single location for arrays and
structs.

We also didn't take into account implicit locations clashing with
explicit locations when assigning locations for their arrays or
structs.

This patch fixes both issues.

V5: fix regression for patch inputs/outputs in tessellation shaders
V4: just use count_attribute_slots() to get the number of slots,
also calculate the correct number of slots to reserve for gs and
tess stages by making use of the new get_varying_type() helper.
V3: handle arrays of structs
V2: also fix for arrays of arrays and structs.

Acked-by: Anuj Phogat <anuj.phogat at gmail.com>
Reviewed-by: Edward O'Callaghan <eocallaghan at alterapraxis.com>

---

 src/glsl/link_varyings.cpp |   79 +++++++++++++++++++++++++++++++++++++-------
 1 file changed, 67 insertions(+), 12 deletions(-)

diff --git a/src/glsl/link_varyings.cpp b/src/glsl/link_varyings.cpp
index 863a399..1da0c9e 100644
--- a/src/glsl/link_varyings.cpp
+++ b/src/glsl/link_varyings.cpp
@@ -825,7 +825,8 @@ public:
                    gl_shader_stage consumer_stage);
    ~varying_matches();
    void record(ir_variable *producer_var, ir_variable *consumer_var);
-   unsigned assign_locations(uint64_t reserved_slots, bool separate_shader);
+   unsigned assign_locations(struct gl_shader_program *prog,
+                             uint64_t reserved_slots, bool separate_shader);
    void store_locations() const;
 
 private:
@@ -1031,7 +1032,9 @@ varying_matches::record(ir_variable *producer_var, ir_variable *consumer_var)
  * passed to varying_matches::record().
  */
 unsigned
-varying_matches::assign_locations(uint64_t reserved_slots, bool separate_shader)
+varying_matches::assign_locations(struct gl_shader_program *prog,
+                                  uint64_t reserved_slots,
+                                  bool separate_shader)
 {
    /* We disable varying sorting for separate shader programs for the
     * following reasons:
@@ -1068,10 +1071,20 @@ varying_matches::assign_locations(uint64_t reserved_slots, bool separate_shader)
    for (unsigned i = 0; i < this->num_matches; i++) {
       unsigned *location = &generic_location;
 
-      if ((this->matches[i].consumer_var &&
-           this->matches[i].consumer_var->data.patch) ||
-          (this->matches[i].producer_var &&
-           this->matches[i].producer_var->data.patch))
+      const ir_variable *var;
+      const glsl_type *type;
+      bool is_vertex_input = false;
+      if (matches[i].consumer_var) {
+         var = matches[i].consumer_var;
+         type = get_varying_type(var, consumer_stage);
+         if (consumer_stage == MESA_SHADER_VERTEX)
+            is_vertex_input = true;
+      } else {
+         var = matches[i].producer_var;
+         type = get_varying_type(var, producer_stage);
+      }
+
+      if (var->data.patch)
          location = &generic_patch_location;
 
       /* Advance to the next slot if this varying has a different packing
@@ -1083,9 +1096,45 @@ varying_matches::assign_locations(uint64_t reserved_slots, bool separate_shader)
           != this->matches[i].packing_class) {
          *location = ALIGN(*location, 4);
       }
-      while ((*location < MAX_VARYING * 4u) &&
-            (reserved_slots & (1u << *location / 4u))) {
-         *location = ALIGN(*location + 1, 4);
+
+      unsigned num_elements =  type->count_attribute_slots(is_vertex_input);
+      unsigned slot_end = this->disable_varying_packing ? 4 :
+         type->without_array()->vector_elements;
+      slot_end += *location - 1;
+
+      /* FIXME: We could be smarter in the below code and loop back over
+       * trying to fill any locations that we skipped because we couldn't pack
+       * the varying between an explicit location. For now just let the user
+       * hit the linking error if we run out of room and suggest they use
+       * explicit locations.
+       */
+      for (unsigned j = 0; j < num_elements; j++) {
+         while ((slot_end < MAX_VARYING * 4u) &&
+                ((reserved_slots & (1u << *location / 4u) ||
+                 (reserved_slots & (1u << slot_end / 4u))))) {
+
+            *location = ALIGN(*location + 1, 4);
+            slot_end = *location;
+
+            /* reset the counter and try again */
+            j = 0;
+         }
+
+         /* Increase the slot to make sure there is enough room for next
+          * array element.
+          */
+         if (this->disable_varying_packing)
+            slot_end += 4;
+         else
+            slot_end += type->without_array()->vector_elements;
+      }
+
+      if (!var->data.patch && *location >= MAX_VARYING * 4u) {
+         linker_error(prog, "insufficient contiguous locations available for "
+                      "%s it is possible an array or struct could not be "
+                      "packed between varyings with explicit locations. Try "
+                      "using an explicit location for arrays and structs.",
+                      var->name);
       }
 
       this->matches[i].generic_location = *location;
@@ -1473,8 +1522,14 @@ reserved_varying_slot(struct gl_shader *stage, ir_variable_mode io_mode)
          continue;
 
       var_slot = var->data.location - VARYING_SLOT_VAR0;
-      if (var_slot >= 0 && var_slot < MAX_VARYING)
-         slots |= 1u << var_slot;
+
+      unsigned num_elements = get_varying_type(var, stage->Stage)
+         ->count_attribute_slots(stage->Stage == MESA_SHADER_VERTEX);
+      for (unsigned i = 0; i < num_elements; i++) {
+         if (var_slot >= 0 && var_slot < MAX_VARYING)
+            slots |= 1u << var_slot;
+         var_slot += 1;
+      }
    }
 
    return slots;
@@ -1660,7 +1715,7 @@ assign_varying_locations(struct gl_context *ctx,
       reserved_varying_slot(producer, ir_var_shader_out) |
       reserved_varying_slot(consumer, ir_var_shader_in);
 
-   const unsigned slots_used = matches.assign_locations(reserved_slots,
+   const unsigned slots_used = matches.assign_locations(prog, reserved_slots,
                                                         prog->SeparateShader);
    matches.store_locations();