gallium/util: Add util_set_shader_buffers_mask helper

Conceptually follows util_set_vertex_buffers_mask but for SSBOs.

v2: Fix missing ~ when clearing mask. Adjust mask behaviour to match
freedreno/v3d when buffer == NULL.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Eric Anholt <eric@anholt.net>

src/gallium/auxiliary/util/u_helpers.c

@@ -101,6 +101,43 @@ void util_set_vertex_buffers_count(struct pipe_vertex_buffer *dst,
    *dst_count = util_last_bit(enabled_buffers);
 }
 
+/**
+ * This function is used to copy an array of pipe_shader_buffer structures,
+ * while properly referencing the pipe_shader_buffer::buffer member.
+ *
+ * \sa util_set_vertex_buffer_mask
+ */
+void util_set_shader_buffers_mask(struct pipe_shader_buffer *dst,
+                                  uint32_t *enabled_buffers,
+                                  const struct pipe_shader_buffer *src,
+                                  unsigned start_slot, unsigned count)
+{
+   unsigned i;
+
+   dst += start_slot;
+
+   if (src) {
+      for (i = 0; i < count; i++) {
+         pipe_resource_reference(&dst[i].buffer, src[i].buffer);
+
+         if (src[i].buffer)
+            *enabled_buffers |= (1ull << (start_slot + i));
+         else
+            *enabled_buffers &= ~(1ull << (start_slot + i));
+      }
+
+      /* Copy over the other members of pipe_shader_buffer. */
+      memcpy(dst, src, count * sizeof(struct pipe_shader_buffer));
+   }
+   else {
+      /* Unreference the buffers. */
+      for (i = 0; i < count; i++)
+         pipe_resource_reference(&dst[i].buffer, NULL);
+
+      *enabled_buffers &= ~(((1ull << count) - 1) << start_slot);
+   }
+}
+
 /**
  * Given a user index buffer, save the structure to "saved", and upload it.
  */

src/gallium/auxiliary/util/u_helpers.h

@@ -46,6 +46,11 @@ void util_set_vertex_buffers_count(struct pipe_vertex_buffer *dst,
                                    const struct pipe_vertex_buffer *src,
                                    unsigned start_slot, unsigned count);
 
+void util_set_shader_buffers_mask(struct pipe_shader_buffer *dst,
+                                  uint32_t *enabled_buffers,
+                                  const struct pipe_shader_buffer *src,
+                                  unsigned start_slot, unsigned count);
+
 bool util_upload_index_buffer(struct pipe_context *pipe,
                               const struct pipe_draw_info *info,
                               struct pipe_resource **out_buffer,