[Mesa-dev] [PATCH 1/7] glsl: Adds an horizontal_location fields to ir_variable.

[Vincent Lejeune]

This field allows to address output variables more precisely
(varyings won't have to "hold" a whole register if they are not vec4).
---
 src/glsl/ir.cpp       |    1 +
 src/glsl/ir.h         |   22 ++++++++++++++++++++++
 src/glsl/ir_clone.cpp |    1 +
 src/glsl/linker.cpp   |    6 +++++-
 4 files changed, 29 insertions(+), 1 deletions(-)

diff --git a/src/glsl/ir.cpp b/src/glsl/ir.cpp
index a5eca5a..a4c93ce 100644
--- a/src/glsl/ir.cpp
+++ b/src/glsl/ir.cpp
@@ -1335,6 +1335,7 @@ ir_variable::ir_variable(const struct glsl_type *type, const char *name,
    this->pixel_center_integer = false;
    this->depth_layout = ir_depth_layout_none;
    this->used = false;
+   this->horizontal_location = 0;
 
    if (type && type->base_type == GLSL_TYPE_SAMPLER)
       this->read_only = true;
diff --git a/src/glsl/ir.h b/src/glsl/ir.h
index 1faae3c..cf0e444 100644
--- a/src/glsl/ir.h
+++ b/src/glsl/ir.h
@@ -396,6 +396,28 @@ public:
     * slot has not been assigned, the value will be -1.
     */
    int location;
+   
+   /**
+    * Storage starting component for this variable
+    * 
+    * Variable storage can be 4-bytes aligned instead of 16-bytes aligned to
+    * preserve space, for instance a vec2 can be stored in FILE[location].yz
+    * and in this case, its starting_component is y (eq to 1).
+    * 
+    * Register can be seen as a 2D array as follow :
+    * - Locations are assigned to rows,
+    * - Components are assigned to columns.
+    *
+    *  0:  [ 0.x  0.y  0.z  0.w]
+    *  1:  [ 1.x  1.y  1.z  1.w]
+    *  2:  [ 2.x  2.y  2.z  2.w]
+    *  ...
+    *  n:  [ n.x  n.y  n.z  n.w]
+    *
+    * Thus we refers this as "horizontal_location" (vertical location is 
+    * the above "location" field).
+    */
+    unsigned horizontal_location:2;
 
    /**
     * Built-in state that backs this uniform
diff --git a/src/glsl/ir_clone.cpp b/src/glsl/ir_clone.cpp
index c63615c..17e800a 100644
--- a/src/glsl/ir_clone.cpp
+++ b/src/glsl/ir_clone.cpp
@@ -46,6 +46,7 @@ ir_variable::clone(void *mem_ctx, struct hash_table *ht) const
    var->invariant = this->invariant;
    var->interpolation = this->interpolation;
    var->location = this->location;
+   var->horizontal_location = this->horizontal_location;
    var->warn_extension = this->warn_extension;
    var->origin_upper_left = this->origin_upper_left;
    var->pixel_center_integer = this->pixel_center_integer;
diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 5095751..8e690ac 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -1458,6 +1458,8 @@ private:
     * variable.  -1 if a location hasn't been assigned yet.
     */
    int location;
+   
+   unsigned horizontal_location;
 
    /**
     * If location != -1, the number of vector elements in this variable, or 1
@@ -1496,6 +1498,7 @@ tfeedback_decl::init(struct gl_context *ctx, struct gl_shader_program *prog,
     */
 
    this->location = -1;
+   this->horizontal_location = 0;
    this->orig_name = input;
    this->is_clip_distance_mesa = false;
 
@@ -1602,6 +1605,7 @@ tfeedback_decl::assign_location(struct gl_context *ctx,
       this->vector_elements = output_var->type->vector_elements;
       this->matrix_columns = output_var->type->matrix_columns;
       this->type = output_var->type->gl_type;
+      this->horizontal_location = output_var->horizontal_location;
    }
 
    /* From GL_EXT_transform_feedback:
@@ -1687,7 +1691,7 @@ tfeedback_decl::store(struct gl_context *ctx, struct gl_shader_program *prog,
       for (unsigned v = 0; v < this->matrix_columns; ++v) {
          unsigned num_components = this->vector_elements;
          assert(info->NumOutputs < max_outputs);
-         info->Outputs[info->NumOutputs].ComponentOffset = 0;
+         info->Outputs[info->NumOutputs].ComponentOffset = this->horizontal_location;
          if (this->is_clip_distance_mesa) {
             if (this->is_subscripted) {
                num_components = 1;
-- 
1.7.7