[Mesa-dev] [PATCH] glsl: Handle attribute aliasing in attribute storage limit check.

[Kenneth Graunke]

In various versions of OpenGL and GLSL, it's possible to declare
multiple VS input variables with aliasing attribute locations.

So, when computing the storage requirements for vertex attributes,
we can't simply add up the sizes.  Instead, we need to look at the
enabled slots.

This patch begins tracking which attributes are double types that
are larger than 128-bits (i.e. take up two vec4 slots).  We then
count normal attributes once, and count the double-size attributes
a second time.

Fixes deQP functional.attribute_location.bind_aliasing.max_cond_* tests
on i965, which regressed with commit ad208d975a6d3aebe14f7c2c16039ee20.

Cc: "10.6 11.0" <mesa-stable at lists.freedesktop.org>
Cc: Matt Turner <mattst88 at gmail.com.
Cc: Ilia Mirkin <imirkin at alum.mit.edu>
Cc: Dave Airlie <airlied at gmail.com>
Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
---
 src/glsl/linker.cpp | 64 ++++++++++++++++++++++++++++++-----------------------
 1 file changed, 36 insertions(+), 28 deletions(-)

diff --git a/src/glsl/linker.cpp b/src/glsl/linker.cpp
index 47f7d25..934062f 100644
--- a/src/glsl/linker.cpp
+++ b/src/glsl/linker.cpp
@@ -2339,6 +2339,7 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
     */
    unsigned used_locations = (max_index >= 32)
       ? ~0 : ~((1 << max_index) - 1);
+   unsigned double_storage_locations = 0;
 
    assert((target_index == MESA_SHADER_VERTEX)
 	  || (target_index == MESA_SHADER_FRAGMENT));
@@ -2452,34 +2453,6 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
 
       const unsigned slots = var->type->count_attribute_slots();
 
-      /* From GL4.5 core spec, section 11.1.1 (Vertex Attributes):
-       *
-       * "A program with more than the value of MAX_VERTEX_ATTRIBS active
-       * attribute variables may fail to link, unless device-dependent
-       * optimizations are able to make the program fit within available
-       * hardware resources. For the purposes of this test, attribute variables
-       * of the type dvec3, dvec4, dmat2x3, dmat2x4, dmat3, dmat3x4, dmat4x3,
-       * and dmat4 may count as consuming twice as many attributes as equivalent
-       * single-precision types. While these types use the same number of
-       * generic attributes as their single-precision equivalents,
-       * implementations are permitted to consume two single-precision vectors
-       * of internal storage for each three- or four-component double-precision
-       * vector."
-       * Until someone has a good reason in Mesa, enforce that now.
-       */
-      if (target_index == MESA_SHADER_VERTEX) {
-	 total_attribs_size += slots;
-	 if (var->type->without_array() == glsl_type::dvec3_type ||
-	     var->type->without_array() == glsl_type::dvec4_type ||
-	     var->type->without_array() == glsl_type::dmat2x3_type ||
-	     var->type->without_array() == glsl_type::dmat2x4_type ||
-	     var->type->without_array() == glsl_type::dmat3_type ||
-	     var->type->without_array() == glsl_type::dmat3x4_type ||
-	     var->type->without_array() == glsl_type::dmat4x3_type ||
-	     var->type->without_array() == glsl_type::dmat4_type)
-	    total_attribs_size += slots;
-      }
-
       /* If the variable is not a built-in and has a location statically
        * assigned in the shader (presumably via a layout qualifier), make sure
        * that it doesn't collide with other assigned locations.  Otherwise,
@@ -2594,6 +2567,38 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
 	    }
 
 	    used_locations |= (use_mask << attr);
+
+            /* From the GL 4.5 core spec, section 11.1.1 (Vertex Attributes):
+             *
+             * "A program with more than the value of MAX_VERTEX_ATTRIBS
+             *  active attribute variables may fail to link, unless
+             *  device-dependent optimizations are able to make the program
+             *  fit within available hardware resources. For the purposes
+             *  of this test, attribute variables of the type dvec3, dvec4,
+             *  dmat2x3, dmat2x4, dmat3, dmat3x4, dmat4x3, and dmat4 may
+             *  count as consuming twice as many attributes as equivalent
+             *  single-precision types. While these types use the same number
+             *  of generic attributes as their single-precision equivalents,
+             *  implementations are permitted to consume two single-precision
+             *  vectors of internal storage for each three- or four-component
+             *  double-precision vector."
+             *
+             * Mark this attribute slot as taking up twice as much space
+             * so we can count it properly against limits.  According to
+             * issue (3) of the GL_ARB_vertex_attrib_64bit behavior, this
+             * is optional behavior, but it seems preferable.
+             */
+            const glsl_type *type = var->type->without_array();
+            if (type == glsl_type::dvec3_type ||
+                type == glsl_type::dvec4_type ||
+                type == glsl_type::dmat2x3_type ||
+                type == glsl_type::dmat2x4_type ||
+                type == glsl_type::dmat3_type ||
+                type == glsl_type::dmat3x4_type ||
+                type == glsl_type::dmat4x3_type ||
+                type == glsl_type::dmat4_type) {
+               double_storage_locations |= (use_mask << attr);
+            }
 	 }
 
 	 continue;
@@ -2605,6 +2610,9 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
    }
 
    if (target_index == MESA_SHADER_VERTEX) {
+      unsigned total_attribs_size =
+         _mesa_bitcount(used_locations & ((1 << max_index) - 1)) +
+         _mesa_bitcount(double_storage_locations);
       if (total_attribs_size > max_index) {
 	 linker_error(prog,
 		      "attempt to use %d vertex attribute slots only %d available ",
-- 
2.5.0