[Mesa-dev] [PATCH v3] glsl/linker: dvec3/dvec4 consume twice input vertex attributes

[Juan A. Suarez Romero]

>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."

This commits makes dvec3, dvec4, dmat2x3, dmat2x4, dmat3, dmat3x4,
dmat4x3 and dmat4 consume twice as many attributes as equivalent
single-precision types.

v3: count doubles as consuming two attributes (Dave Airlie)

Signed-off-by: Antia Puentes <apuentes at igalia.com>
Signed-off-by: Juan A. Suarez Romero <jasuarez at igalia.com>
---
 src/compiler/glsl/linker.cpp | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/compiler/glsl/linker.cpp b/src/compiler/glsl/linker.cpp
index f208d19..ad96a63 100644
--- a/src/compiler/glsl/linker.cpp
+++ b/src/compiler/glsl/linker.cpp
@@ -2873,6 +2873,25 @@ assign_attribute_or_color_locations(gl_shader_program *prog,
       to_assign[i].var->data.location = generic_base + location;
       to_assign[i].var->data.is_unmatched_generic_inout = 0;
       used_locations |= (use_mask << location);
+
+      if (to_assign[i].var->type->without_array()->is_dual_slot_double())
+         double_storage_locations |= (use_mask << location);
+   }
+
+   /* Now that we have all the locations, take in account that dvec3/4 can
+    * require twice the space of single-precision vectors. Check if we run out
+    * of attribute slots.
+    */
+   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 ",
+		      total_attribs_size, max_index);
+	 return false;
+      }
    }
 
    return true;
-- 
2.5.5