linker: Support matrix and array vertex inputs
diff --git a/linker.cpp b/linker.cpp
index 314db0b..1f2cee1 100644
--- a/linker.cpp
+++ b/linker.cpp
@@ -127,6 +127,41 @@
/**
+ * Determine the number of attribute slots required for a particular type
+ *
+ * This code is here because it implements the language rules of a specific
+ * GLSL version. Since it's a property of the language and not a property of
+ * types in general, it doesn't really belong in glsl_type.
+ */
+unsigned
+count_attribute_slots(const glsl_type *t)
+{
+ /* From page 31 (page 37 of the PDF) of the GLSL 1.50 spec:
+ *
+ * "A scalar input counts the same amount against this limit as a vec4,
+ * so applications may want to consider packing groups of four
+ * unrelated float inputs together into a vector to better utilize the
+ * capabilities of the underlying hardware. A matrix input will use up
+ * multiple locations. The number of locations used will equal the
+ * number of columns in the matrix."
+ *
+ * The spec does not explicitly say how arrays are counted. However, it
+ * should be safe to assume the total number of slots consumed by an array
+ * is the number of entries in the array multiplied by the number of slots
+ * consumed by a single element of the array.
+ */
+
+ if (t->is_array())
+ return t->array_size() * count_attribute_slots(t->element_type());
+
+ if (t->is_matrix())
+ return t->matrix_columns;
+
+ return 1;
+}
+
+
+/**
* Verify that a vertex shader executable meets all semantic requirements
*
* \param shader Vertex shader executable to be verified
@@ -434,7 +469,39 @@
}
-void
+/**
+ * Find a contiguous set of available bits in a bitmask
+ *
+ * \param used_mask Bits representing used (1) and unused (0) locations
+ * \param needed_count Number of contiguous bits needed.
+ *
+ * \return
+ * Base location of the available bits on success or -1 on failure.
+ */
+int
+find_available_slots(unsigned used_mask, unsigned needed_count)
+{
+ unsigned needed_mask = (1 << needed_count) - 1;
+ const int max_bit_to_test = (8 * sizeof(used_mask)) - needed_count;
+
+ /* The comparison to 32 is redundant, but without it GCC emits "warning:
+ * cannot optimize possibly infinite loops" for the loop below.
+ */
+ if ((needed_count == 0) || (max_bit_to_test < 0) || (max_bit_to_test > 32))
+ return -1;
+
+ for (int i = 0; i <= max_bit_to_test; i++) {
+ if ((needed_mask & ~used_mask) == needed_mask)
+ return i;
+
+ needed_mask <<= 1;
+ }
+
+ return -1;
+}
+
+
+bool
assign_attribute_locations(glsl_shader *sh,
struct gl_program_parameter_list *attrib)
{
@@ -442,14 +509,19 @@
assert(sh->Type == GL_VERTEX_SHADER);
- /* Operate in a total of three passes.
+ /* Operate in a total of four passes.
*
* 1. Invalidate the location assignments for all vertex shader inputs.
*
* 2. Assign locations for inputs that have user-defined (via
* glBindVertexAttribLocation) locatoins.
*
- * 3. Assign locations to any inputs without assigned locations.
+ * 3. Sort the attributes without assigned locations by number of slots
+ * required in decreasing order. Fragmentation caused by attribute
+ * locations assigned by the application may prevent large attributes
+ * from having enough contiguous space.
+ *
+ * 4. Assign locations to any inputs without assigned locations.
*/
invalidate_variable_locations(sh, ir_var_in, VERT_ATTRIB_GENERIC0);
@@ -459,16 +531,84 @@
ir_variable *const var =
sh->symbols->get_variable(attrib->Parameters[i].Name);
- if (var == NULL)
+ /* Note: attributes that occupy multiple slots, such as arrays or
+ * matrices, may appear in the attrib array multiple times.
+ */
+ if ((var == NULL) || (var->location != -1))
continue;
+ /* From page 61 of the OpenGL 4.0 spec:
+ *
+ * "LinkProgram will fail if the attribute bindings assigned by
+ * BindAttribLocation do not leave not enough space to assign a
+ * location for an active matrix attribute or an active attribute
+ * array, both of which require multiple contiguous generic
+ * attributes."
+ *
+ * Previous versions of the spec contain similar language but omit the
+ * bit about attribute arrays.
+ *
+ * Page 61 of the OpenGL 4.0 spec also says:
+ *
+ * "It is possible for an application to bind more than one
+ * attribute name to the same location. This is referred to as
+ * aliasing. This will only work if only one of the aliased
+ * attributes is active in the executable program, or if no path
+ * through the shader consumes more than one attribute of a set
+ * of attributes aliased to the same location. A link error can
+ * occur if the linker determines that every path through the
+ * shader consumes multiple aliased attributes, but
+ * implementations are not required to generate an error in this
+ * case."
+ *
+ * These two paragraphs are either somewhat contradictory, or I don't
+ * fully understand one or both of them.
+ */
+ /* FINISHME: The code as currently written does not support attribute
+ * FINISHME: location aliasing (see comment above).
+ */
const int attr = attrib->Parameters[i].StateIndexes[0];
+ const unsigned slots = count_attribute_slots(var->type);
+
+ /* Mask representing the contiguous slots that will be used by this
+ * attribute.
+ */
+ const unsigned use_mask = (1 << slots) - 1;
+
+ /* Generate a link error if the set of bits requested for this
+ * attribute overlaps any previously allocated bits.
+ */
+ if ((~(use_mask << attr) & used_locations) != used_locations) {
+ printf("error: insufficient contiguous attribute locations "
+ "available for vertex shader input `%s'",
+ var->name);
+ return false;
+ }
var->location = VERT_ATTRIB_GENERIC0 + attr;
- used_locations |= (1 << attr);
+ used_locations |= (use_mask << attr);
}
}
+ /* Temporary storage for the set of attributes that need locations assigned.
+ */
+ struct temp_attr {
+ unsigned slots;
+ ir_variable *var;
+
+ /* Used below in the call to qsort. */
+ static int compare(const void *a, const void *b)
+ {
+ const temp_attr *const l = (const temp_attr *) a;
+ const temp_attr *const r = (const temp_attr *) b;
+
+ /* Reversed because we want a descending order sort below. */
+ return r->slots - l->slots;
+ }
+ } to_assign[16];
+
+ unsigned num_attr = 0;
+
foreach_list(node, &sh->ir) {
ir_variable *const var = ((ir_instruction *) node)->as_variable();
@@ -480,17 +620,40 @@
if (var->location != -1)
continue;
- /* Find an unused bit in used_locations and assign that as the
- * attribute location.
- */
- for (unsigned i = 0; i < (8 * sizeof(used_locations)); i++) {
- if ((used_locations & (1 << i)) == 0) {
- var->location = VERT_ATTRIB_GENERIC0 + i;
- used_locations |= (1 << i);
- break;
- }
- }
+ to_assign[num_attr].slots = count_attribute_slots(var->type);
+ to_assign[num_attr].var = var;
+ num_attr++;
}
+
+ /* If all of the attributes were assigned locations by the application (or
+ * are built-in attributes with fixed locations), return early. This should
+ * be the common case.
+ */
+ if (num_attr == 0)
+ return true;
+
+ qsort(to_assign, num_attr, sizeof(to_assign[0]), temp_attr::compare);
+
+ for (unsigned i = 0; i < num_attr; i++) {
+ /* Mask representing the contiguous slots that will be used by this
+ * attribute.
+ */
+ const unsigned use_mask = (1 << to_assign[i].slots) - 1;
+
+ int location = find_available_slots(used_locations, to_assign[i].slots);
+
+ if (location < 0) {
+ printf("error: insufficient contiguous attribute locations "
+ "available for vertex shader input `%s'",
+ to_assign[i].var->name);
+ return false;
+ }
+
+ to_assign[i].var->location = VERT_ATTRIB_GENERIC0 + location;
+ used_locations |= (use_mask << location);
+ }
+
+ return true;
}
@@ -573,8 +736,9 @@
assign_uniform_locations(prog);
if (prog->_LinkedShaders[0]->Type == GL_VERTEX_SHADER)
- assign_attribute_locations(prog->_LinkedShaders[0],
- prog->Attributes);
+ if (!assign_attribute_locations(prog->_LinkedShaders[0],
+ prog->Attributes))
+ goto done;
/* FINISHME: Assign vertex shader output / fragment shader input
* FINISHME: locations.