[Mesa-dev] [PATCH 6/7] linker: Set binding for all elements of UBO array

[Ian Romanick]

From: Ian Romanick <ian.d.romanick at intel.com>

Previously, a UBO like

    layout(binding=2) uniform U {
        ...
    } my_constants[4];

wouldn't get any bindings set.  The code would try to set the binding of
U, but that would fail.  It should instead set the bindings for U[0],
U[1], ...

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=76323
Cc: "10.1" <mesa-stable at lists.freedesktop.org>
Cc: github at socker.lepus.uberspace.de
---
 src/glsl/link_uniform_initializers.cpp | 36 ++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

diff --git a/src/glsl/link_uniform_initializers.cpp b/src/glsl/link_uniform_initializers.cpp
index 491eb69..e60bb64 100644
--- a/src/glsl/link_uniform_initializers.cpp
+++ b/src/glsl/link_uniform_initializers.cpp
@@ -262,8 +262,40 @@ link_set_uniform_initializers(struct gl_shader_program *prog)
             } else if (var->is_in_uniform_block()) {
                const glsl_type *const iface_type = var->get_interface_type();
 
-               linker::set_block_binding(prog, iface_type->name,
-                                         var->data.binding);
+               /* If the variable is an array and it is an interface instance,
+                * we need to set the binding for each array element.  Just
+                * checking that the variable is an array is not sufficient.
+                * The variable could be an array element of a uniform block
+                * that lacks an instance name.  For example:
+                *
+                *     uniform U {
+                *         float f[4];
+                *     };
+                *
+                * In this case "f" would pass is_in_uniform_block (above) and
+                * type->is_array(), but it will fail is_interface_instance().
+                */
+               if (var->is_interface_instance() && var->type->is_array()) {
+                  for (unsigned i = 0; i < var->type->length; i++) {
+                     const char *name =
+                        ralloc_asprintf(mem_ctx, "%s[%u]", iface_type->name, i);
+
+                     /* Section 4.4.3 (Uniform Block Layout Qualifiers) of the
+                      * GLSL 4.20 spec says:
+                      *
+                      *     "If the binding identifier is used with a uniform
+                      *     block instanced as an array then the first element
+                      *     of the array takes the specified block binding and
+                      *     each subsequent element takes the next consecutive
+                      *     uniform block binding point."
+                      */
+                     linker::set_block_binding(prog, name,
+                                               var->data.binding + i);
+                  }
+               } else {
+                  linker::set_block_binding(prog, iface_type->name,
+                                            var->data.binding);
+               }
             } else {
                assert(!"Explicit binding not on a sampler or UBO.");
             }
-- 
1.8.1.4