glsl ubo/ssbo: Add lower_buffer_access class

This class has code that will be shared by lower_ubo_reference and
lower_shared_reference. (lower_shared_reference will be used to
support compute shader shared variables.)

v2:
 * Add lower_buffer_access.h to makefile (Emil)
 * Remove static is_dereferenced_thing_row_major from
   lower_buffer_access.cpp. This will become a lower_buffer_access
   method in the next commit.
 * Pass mem_ctx as parameter rather than using a member variable (Iago)

Signed-off-by: Jordan Justen <[email protected]>
Reviewed-by: Iago Toral Quiroga <[email protected]>
Reviewed-by: Kristian Høgsberg <[email protected]>

1 files changed, 216 insertions, 0 deletions

diff --git a/src/glsl/lower_buffer_access.cpp b/src/glsl/lower_buffer_access.cpp
new file mode 100644
index 00000000000..7428742adfc
--- /dev/null
+++ b/src/glsl/lower_buffer_access.cpp
@@ -0,0 +1,216 @@
+/*
+ * Copyright (c) 2015 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+/**
+ * \file lower_buffer_access.cpp
+ *
+ * Helper for IR lowering pass to replace dereferences of buffer object based
+ * shader variables with intrinsic function calls.
+ *
+ * This helper is used by lowering passes for UBOs, SSBOs and compute shader
+ * shared variables.
+ */
+
+#include "lower_buffer_access.h"
+#include "ir_builder.h"
+#include "main/macros.h"
+#include "util/list.h"
+#include "glsl_parser_extras.h"
+
+using namespace ir_builder;
+
+namespace lower_buffer_access {
+
+static inline int
+writemask_for_size(unsigned n)
+{
+   return ((1 << n) - 1);
+}
+
+/**
+ * Takes a deref and recursively calls itself to break the deref down to the
+ * point that the reads or writes generated are contiguous scalars or vectors.
+ */
+void
+lower_buffer_access::emit_access(void *mem_ctx,
+                                 bool is_write,
+                                 ir_dereference *deref,
+                                 ir_variable *base_offset,
+                                 unsigned int deref_offset,
+                                 bool row_major,
+                                 int matrix_columns,
+                                 unsigned int packing,
+                                 unsigned int write_mask)
+{
+   if (deref->type->is_record()) {
+      unsigned int field_offset = 0;
+
+      for (unsigned i = 0; i < deref->type->length; i++) {
+         const struct glsl_struct_field *field =
+            &deref->type->fields.structure[i];
+         ir_dereference *field_deref =
+            new(mem_ctx) ir_dereference_record(deref->clone(mem_ctx, NULL),
+                                               field->name);
+
+         field_offset =
+            glsl_align(field_offset,
+                       field->type->std140_base_alignment(row_major));
+
+         emit_access(mem_ctx, is_write, field_deref, base_offset,
+                     deref_offset + field_offset,
+                     row_major, 1, packing,
+                     writemask_for_size(field_deref->type->vector_elements));
+
+         field_offset += field->type->std140_size(row_major);
+      }
+      return;
+   }
+
+   if (deref->type->is_array()) {
+      unsigned array_stride = packing == GLSL_INTERFACE_PACKING_STD430 ?
+         deref->type->fields.array->std430_array_stride(row_major) :
+         glsl_align(deref->type->fields.array->std140_size(row_major), 16);
+
+      for (unsigned i = 0; i < deref->type->length; i++) {
+         ir_constant *element = new(mem_ctx) ir_constant(i);
+         ir_dereference *element_deref =
+            new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL),
+                                              element);
+         emit_access(mem_ctx, is_write, element_deref, base_offset,
+                     deref_offset + i * array_stride,
+                     row_major, 1, packing,
+                     writemask_for_size(element_deref->type->vector_elements));
+      }
+      return;
+   }
+
+   if (deref->type->is_matrix()) {
+      for (unsigned i = 0; i < deref->type->matrix_columns; i++) {
+         ir_constant *col = new(mem_ctx) ir_constant(i);
+         ir_dereference *col_deref =
+            new(mem_ctx) ir_dereference_array(deref->clone(mem_ctx, NULL), col);
+
+         if (row_major) {
+            /* For a row-major matrix, the next column starts at the next
+             * element.
+             */
+            int size_mul = deref->type->is_double() ? 8 : 4;
+            emit_access(mem_ctx, is_write, col_deref, base_offset,
+                        deref_offset + i * size_mul,
+                        row_major, deref->type->matrix_columns, packing,
+                        writemask_for_size(col_deref->type->vector_elements));
+         } else {
+            int size_mul;
+
+            /* std430 doesn't round up vec2 size to a vec4 size */
+            if (packing == GLSL_INTERFACE_PACKING_STD430 &&
+                deref->type->vector_elements == 2 &&
+                !deref->type->is_double()) {
+               size_mul = 8;
+            } else {
+               /* std140 always rounds the stride of arrays (and matrices) to a
+                * vec4, so matrices are always 16 between columns/rows. With
+                * doubles, they will be 32 apart when there are more than 2 rows.
+                *
+                * For both std140 and std430, if the member is a
+                * three-'component vector with components consuming N basic
+                * machine units, the base alignment is 4N. For vec4, base
+                * alignment is 4N.
+                */
+               size_mul = (deref->type->is_double() &&
+                           deref->type->vector_elements > 2) ? 32 : 16;
+            }
+
+            emit_access(mem_ctx, is_write, col_deref, base_offset,
+                        deref_offset + i * size_mul,
+                        row_major, deref->type->matrix_columns, packing,
+                        writemask_for_size(col_deref->type->vector_elements));
+         }
+      }
+      return;
+   }
+
+   assert(deref->type->is_scalar() || deref->type->is_vector());
+
+   if (!row_major) {
+      ir_rvalue *offset =
+         add(base_offset, new(mem_ctx) ir_constant(deref_offset));
+      unsigned mask =
+         is_write ? write_mask : (1 << deref->type->vector_elements) - 1;
+      insert_buffer_access(mem_ctx, deref, deref->type, offset, mask, -1);
+   } else {
+      unsigned N = deref->type->is_double() ? 8 : 4;
+
+      /* We're dereffing a column out of a row-major matrix, so we
+       * gather the vector from each stored row.
+      */
+      assert(deref->type->base_type == GLSL_TYPE_FLOAT ||
+             deref->type->base_type == GLSL_TYPE_DOUBLE);
+      /* Matrices, row_major or not, are stored as if they were
+       * arrays of vectors of the appropriate size in std140.
+       * Arrays have their strides rounded up to a vec4, so the
+       * matrix stride is always 16. However a double matrix may either be 16
+       * or 32 depending on the number of columns.
+       */
+      assert(matrix_columns <= 4);
+      unsigned matrix_stride = 0;
+      /* Matrix stride for std430 mat2xY matrices are not rounded up to
+       * vec4 size. From OpenGL 4.3 spec, section 7.6.2.2 "Standard Uniform
+       * Block Layout":
+       *
+       * "2. If the member is a two- or four-component vector with components
+       * consuming N basic machine units, the base alignment is 2N or 4N,
+       * respectively." [...]
+       * "4. If the member is an array of scalars or vectors, the base alignment
+       * and array stride are set to match the base alignment of a single array
+       * element, according to rules (1), (2), and (3), and rounded up to the
+       * base alignment of a vec4." [...]
+       * "7. If the member is a row-major matrix with C columns and R rows, the
+       * matrix is stored identically to an array of R row vectors with C
+       * components each, according to rule (4)." [...]
+       * "When using the std430 storage layout, shader storage blocks will be
+       * laid out in buffer storage identically to uniform and shader storage
+       * blocks using the std140 layout, except that the base alignment and
+       * stride of arrays of scalars and vectors in rule 4 and of structures in
+       * rule 9 are not rounded up a multiple of the base alignment of a vec4."
+       */
+      if (packing == GLSL_INTERFACE_PACKING_STD430 && matrix_columns == 2)
+         matrix_stride = 2 * N;
+      else
+         matrix_stride = glsl_align(matrix_columns * N, 16);
+
+      const glsl_type *deref_type = deref->type->base_type == GLSL_TYPE_FLOAT ?
+         glsl_type::float_type : glsl_type::double_type;
+
+      for (unsigned i = 0; i < deref->type->vector_elements; i++) {
+         ir_rvalue *chan_offset =
+            add(base_offset,
+                new(mem_ctx) ir_constant(deref_offset + i * matrix_stride));
+         if (!is_write || ((1U << i) & write_mask))
+            insert_buffer_access(mem_ctx, deref, deref_type, chan_offset,
+                                 (1U << i), i);
+      }
+   }
+}
+
+} /* namespace lower_buffer_access */