glsl: add gl_linked_shader::SourceChecksum

for debugging

v2: wrap all checksums in #ifdef DEBUG

Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>

src/compiler/glsl/linker.cpp

@@ -2297,6 +2297,16 @@ link_intrastage_shaders(void *mem_ctx,
    if (ctx->Const.VertexID_is_zero_based)
       lower_vertex_id(linked);
 
+#ifdef DEBUG
+   /* Compute the source checksum. */
+   linked->SourceChecksum = 0;
+   for (unsigned i = 0; i < num_shaders; i++) {
+      if (shader_list[i] == NULL)
+         continue;
+      linked->SourceChecksum ^= shader_list[i]->SourceChecksum;
+   }
+#endif
+
    return linked;
 }