glsl: Add support for image binding qualifiers.

Support for binding an image to an image unit explicitly in the shader
source is required by both GLSL 4.2 and GLSL ES 3.1, but not by the
original ARB_shader_image_load_store extension.

Reviewed-by: Timothy Arceri <t_arceri@yahoo.com.au>

src/glsl/ast_to_hir.cpp

@@ -2181,10 +2181,20 @@ validate_binding_qualifier(struct _mesa_glsl_parse_state *state,
 
          return false;
       }
+   } else if (state->is_version(420, 310) &&
+              var->type->without_array()->is_image()) {
+      assert(ctx->Const.MaxImageUnits <= MAX_IMAGE_UNITS);
+      if (max_index >= ctx->Const.MaxImageUnits) {
+         _mesa_glsl_error(loc, state, "Image binding %d exceeds the "
+                          " maximum number of image units (%d)", max_index,
+                          ctx->Const.MaxImageUnits);
+         return false;
+      }
+
    } else {
       _mesa_glsl_error(loc, state,
                        "the \"binding\" qualifier only applies to uniform "
-                       "blocks, samplers, atomic counters, or arrays thereof");
+                       "blocks, opaque variables, or arrays thereof");
       return false;
    }
 

src/glsl/link_uniform_initializers.cpp

@@ -100,8 +100,13 @@ copy_constant_to_storage(union gl_constant_value *storage,
    }
 }
 
+/**
+ * Initialize an opaque uniform from the value of an explicit binding
+ * qualifier specified in the shader.  Atomic counters are different because
+ * they have no storage and should be handled elsewhere.
+ */
 void
-set_sampler_binding(gl_shader_program *prog, const char *name, int binding)
+set_opaque_binding(gl_shader_program *prog, const char *name, int binding)
 {
    struct gl_uniform_storage *const storage =
       get_storage(prog->UniformStorage, prog->NumUniformStorage, name);
@@ -127,11 +132,20 @@ set_sampler_binding(gl_shader_program *prog, const char *name, int binding)
    for (int sh = 0; sh < MESA_SHADER_STAGES; sh++) {
       gl_shader *shader = prog->_LinkedShaders[sh];
 
-      if (shader && storage->sampler[sh].active) {
-         for (unsigned i = 0; i < elements; i++) {
-            unsigned index = storage->sampler[sh].index + i;
+      if (shader) {
+         if (storage->type->base_type == GLSL_TYPE_SAMPLER &&
+             storage->sampler[sh].active) {
+            for (unsigned i = 0; i < elements; i++) {
+               const unsigned index = storage->sampler[sh].index + i;
+               shader->SamplerUnits[index] = storage->storage[i].i;
+            }
 
-            shader->SamplerUnits[index] = storage->storage[i].i;
+         } else if (storage->type->base_type == GLSL_TYPE_IMAGE &&
+                    storage->image[sh].active) {
+            for (unsigned i = 0; i < elements; i++) {
+               const unsigned index = storage->image[sh].index + i;
+               shader->ImageUnits[index] = storage->storage[i].i;
+            }
          }
       }
    }
@@ -267,8 +281,9 @@ link_set_uniform_initializers(struct gl_shader_program *prog,
          if (var->data.explicit_binding) {
             const glsl_type *const type = var->type;
 
-            if (type->without_array()->is_sampler()) {
-               linker::set_sampler_binding(prog, var->name, var->data.binding);
+            if (type->without_array()->is_sampler() ||
+                type->without_array()->is_image()) {
+               linker::set_opaque_binding(prog, var->name, var->data.binding);
             } else if (var->is_in_buffer_block()) {
                const glsl_type *const iface_type = var->get_interface_type();