mesa/glsl: introduce a remap table for uniform locations

Patch adds a remap table for uniforms that is used to provide a mapping
from application specified uniform location to actual location in the
UniformStorage. Existing UniformLocationBaseScale usage is removed as
table can be used to set sequential values for array uniform elements.

This mapping helps to implement GL_ARB_explicit_uniform_location so that
uniforms locations can be reorganized and handled in a more easy manner.

v2: small fixes + rename parameters for merge and split functions (Ian)
    improve documentation, remove old check for location bounds (Eric)

Signed-off-by: Tapani Pälli <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>
Reviewed-by: Eric Anholt <[email protected]>

2 files changed, 30 insertions, 11 deletions

diff --git a/src/glsl/ir_uniform.h b/src/glsl/ir_uniform.h
index 7508f795d08..3508509d4d0 100644
--- a/src/glsl/ir_uniform.h
+++ b/src/glsl/ir_uniform.h
@@ -178,6 +178,12 @@ struct gl_uniform_storage {
     * an atomic counter.
     */
    int atomic_buffer_index;
+
+   /**
+    * The 'base location' for this uniform in the uniform remap table. For
+    * arrays this is the first element in the array.
+    */
+   unsigned remap_location;
 };
 
 #ifdef __cplusplus
diff --git a/src/glsl/link_uniforms.cpp b/src/glsl/link_uniforms.cpp
index 1c451e7f51c..3fedf313cbd 100644
--- a/src/glsl/link_uniforms.cpp
+++ b/src/glsl/link_uniforms.cpp
@@ -799,6 +799,10 @@ link_assign_uniform_locations(struct gl_shader_program *prog)
    prog->UniformStorage = NULL;
    prog->NumUserUniformStorage = 0;
 
+   ralloc_free(prog->UniformRemapTable);
+   prog->UniformRemapTable = NULL;
+   prog->NumUniformRemapTable = 0;
+
    if (prog->UniformHash != NULL) {
       prog->UniformHash->clear();
    } else {
@@ -911,19 +915,28 @@ link_assign_uniform_locations(struct gl_shader_program *prog)
              sizeof(prog->_LinkedShaders[i]->SamplerTargets));
    }
 
-   /* Determine the size of the largest uniform array queryable via
-    * glGetUniformLocation.  Using this as the location scale guarantees that
-    * there is enough "room" for the array index to be stored in the low order
-    * part of the uniform location.  It also makes the locations be more
-    * tightly packed.
-    */
-   unsigned max_array_size = 1;
+   /* Build the uniform remap table that is used to set/get uniform locations */
    for (unsigned i = 0; i < num_user_uniforms; i++) {
-      if (uniforms[i].array_elements > max_array_size)
-         max_array_size = uniforms[i].array_elements;
-   }
 
-   prog->UniformLocationBaseScale = max_array_size;
+      /* how many new entries for this uniform? */
+      const unsigned entries = MAX2(1, uniforms[i].array_elements);
+
+      /* resize remap table to fit new entries */
+      prog->UniformRemapTable =
+         reralloc(prog,
+                  prog->UniformRemapTable,
+                  gl_uniform_storage *,
+                  prog->NumUniformRemapTable + entries);
+
+      /* set pointers for this uniform */
+      for (unsigned j = 0; j < entries; j++)
+         prog->UniformRemapTable[prog->NumUniformRemapTable+j] = &uniforms[i];
+
+      /* set the base location in remap table for the uniform */
+      uniforms[i].remap_location = prog->NumUniformRemapTable;
+
+      prog->NumUniformRemapTable += entries;
+   }
 
 #ifndef NDEBUG
    for (unsigned i = 0; i < num_user_uniforms; i++) {