[Mesa-dev] [PATCH 07/12] glsl: Refactor matrix stride calculation into a utility function

[Ian Romanick]

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

Signed-off-by: Ian Romanick <ian.d.romanick at intel.com>
---
 src/compiler/glsl/link_uniforms.cpp | 57 ++++++++++++++++++++++++++++++-------
 src/compiler/glsl/linker.h          |  4 +++
 2 files changed, 50 insertions(+), 11 deletions(-)

diff --git a/src/compiler/glsl/link_uniforms.cpp b/src/compiler/glsl/link_uniforms.cpp
index be39c375..1955f62 100644
--- a/src/compiler/glsl/link_uniforms.cpp
+++ b/src/compiler/glsl/link_uniforms.cpp
@@ -398,6 +398,48 @@ private:
 
 } /* anonymous namespace */
 
+unsigned
+link_calculate_matrix_stride(const glsl_type *matrix, bool row_major,
+                             enum glsl_interface_packing packing)
+{
+   const unsigned N = matrix->is_double() ? 8 : 4;
+   const unsigned items =
+      row_major ? matrix->matrix_columns : matrix->vector_elements;
+
+   assert(items <= 4);
+
+   /* Matrix stride for std430 mat2xY matrices are not rounded up to
+    * vec4 size.
+    *
+    * Section 7.6.2.2 "Standard Uniform Block Layout" of the OpenGL 4.3 spec
+    * says:
+    *
+    *    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.
+    */
+   return packing == GLSL_INTERFACE_PACKING_STD430
+      ? (items < 3 ? items * N : glsl_align(items * N, 16))
+      : glsl_align(items * N, 16);
+}
+
 /**
  * Class to help parcel out pieces of backing storage to uniforms
  *
@@ -856,17 +898,10 @@ private:
          }
 
          if (type->without_array()->is_matrix()) {
-            const glsl_type *matrix = type->without_array();
-            const unsigned N = matrix->is_double() ? 8 : 4;
-            const unsigned items =
-               row_major ? matrix->matrix_columns : matrix->vector_elements;
-
-            assert(items <= 4);
-            if (packing == GLSL_INTERFACE_PACKING_STD430)
-               this->uniforms[id].matrix_stride = items < 3 ? items * N :
-                                                    glsl_align(items * N, 16);
-            else
-               this->uniforms[id].matrix_stride = glsl_align(items * N, 16);
+            this->uniforms[id].matrix_stride =
+               link_calculate_matrix_stride(type->without_array(),
+                                            row_major,
+                                            packing);
             this->uniforms[id].row_major = row_major;
          } else {
             this->uniforms[id].matrix_stride = 0;
diff --git a/src/compiler/glsl/linker.h b/src/compiler/glsl/linker.h
index 03ed9d5..12a48e0 100644
--- a/src/compiler/glsl/linker.h
+++ b/src/compiler/glsl/linker.h
@@ -92,6 +92,10 @@ link_intrastage_shaders(void *mem_ctx,
                         unsigned num_shaders,
                         bool allow_missing_main);
 
+extern unsigned
+link_calculate_matrix_stride(const glsl_type *matrix, bool row_major,
+                             enum glsl_interface_packing packing);
+
 /**
  * Class for processing all of the leaf fields of a variable that corresponds
  * to a program resource.
-- 
2.9.5