glsl: validate global out xfb_stride qualifiers and set stride on empty buffers

Here we use the built-in validation in
ast_layout_expression::process_qualifier_constant() to check for mismatching
global out strides on buffers in a single shader.

From the ARB_enhanced_layouts spec:

   "While *xfb_stride* can be declared multiple times for the same buffer,
   it is a compile-time or link-time error to have different values
   specified for the stride for the same buffer."

For intrastage validation a new helper link_xfb_stride_layout_qualifiers()
is created. We also take this opportunity to make sure stride is at least
a multiple of 4, we will validate doubles at a later stage.

From the ARB_enhanced_layouts spec:

   "If the buffer is capturing any double-typed outputs, the stride must
   be a multiple of 8, otherwise it must be a multiple of 4, or a
   compile-time or link-time error results."

Finally we update store_tfeedback_info() to apply the strides to
LinkedTransformFeedback and update the buffers bitmask to mark any global
buffers with a stride as active. For example a shader with:

layout (xfb_buffer = 0, xfb_offset = 0)  out vec4 gs_fs;
layout (xfb_buffer = 1, xfb_stride = 64) out;

Is expected to have a buffer bound to both 0 and 1.

From the ARB_enhanced_layouts spec:

   "A binding point requires a bound buffer object if and only if its
   associated stride in the program object used for transform feedback
   primitive capture is non-zero."

Reviewed-by: Dave Airlie <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index 90c3851e72a..1e15b69ab70 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -2337,6 +2337,11 @@ struct gl_shader
    bool origin_upper_left;
    bool pixel_center_integer;
 
+   struct {
+      /** Global xfb_stride out qualifier if any */
+      GLuint BufferStride[MAX_FEEDBACK_BUFFERS];
+   } TransformFeedback;
+
    /**
     * Tessellation Control shader state from layout qualifiers.
     */
@@ -2674,6 +2679,8 @@ struct gl_shader_program
     */
    struct {
       GLenum BufferMode;
+      /** Global xfb_stride out qualifier if any */
+      GLuint BufferStride[MAX_FEEDBACK_BUFFERS];
       GLuint NumVarying;
       GLchar **VaryingNames;  /**< Array [NumVarying] of char * */
    } TransformFeedback;