glsl: Factor out the sampler dim coordinate components switch statement.

I want to reuse this in NIR image intrinsics in backends, which just have
dim/is_array.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3728>

src/compiler/glsl_types.cpp

@@ -2582,29 +2582,8 @@ glsl_type::count_dword_slots(bool is_bindless) const
 int
 glsl_type::coordinate_components() const
 {
-   int size;
-
-   switch (sampler_dimensionality) {
-   case GLSL_SAMPLER_DIM_1D:
-   case GLSL_SAMPLER_DIM_BUF:
-      size = 1;
-      break;
-   case GLSL_SAMPLER_DIM_2D:
-   case GLSL_SAMPLER_DIM_RECT:
-   case GLSL_SAMPLER_DIM_MS:
-   case GLSL_SAMPLER_DIM_EXTERNAL:
-   case GLSL_SAMPLER_DIM_SUBPASS:
-      size = 2;
-      break;
-   case GLSL_SAMPLER_DIM_3D:
-   case GLSL_SAMPLER_DIM_CUBE:
-      size = 3;
-      break;
-   default:
-      assert(!"Should not get here.");
-      size = 1;
-      break;
-   }
+   enum glsl_sampler_dim dim = (enum glsl_sampler_dim)sampler_dimensionality;
+   int size = glsl_get_sampler_dim_coordinate_components(dim);
 
    /* Array textures need an additional component for the array index, except
     * for cubemap array images that behave like a 2D array of interleaved
@@ -2937,3 +2916,28 @@ glsl_type::cl_size() const
    }
    return 1;
 }
+
+extern "C" {
+
+int
+glsl_get_sampler_dim_coordinate_components(enum glsl_sampler_dim dim)
+{
+   switch (dim) {
+   case GLSL_SAMPLER_DIM_1D:
+   case GLSL_SAMPLER_DIM_BUF:
+      return 1;
+   case GLSL_SAMPLER_DIM_2D:
+   case GLSL_SAMPLER_DIM_RECT:
+   case GLSL_SAMPLER_DIM_MS:
+   case GLSL_SAMPLER_DIM_EXTERNAL:
+   case GLSL_SAMPLER_DIM_SUBPASS:
+      return 2;
+   case GLSL_SAMPLER_DIM_3D:
+   case GLSL_SAMPLER_DIM_CUBE:
+      return 3;
+   default:
+      unreachable("Unknown sampler dim");
+   }
+}
+
+}

src/compiler/glsl_types.h

@@ -60,10 +60,6 @@ void encode_type_to_blob(struct blob *blob, const struct glsl_type *type);
 
 const struct glsl_type *decode_type_from_blob(struct blob_reader *blob);
 
-#ifdef __cplusplus
-}
-#endif
-
 typedef void (*glsl_type_size_align_func)(const struct glsl_type *type,
                                           unsigned *size, unsigned *align);
 
@@ -231,6 +227,9 @@ enum glsl_sampler_dim {
    GLSL_SAMPLER_DIM_SUBPASS_MS, /* for multisampled vulkan input attachments */
 };
 
+int
+glsl_get_sampler_dim_coordinate_components(enum glsl_sampler_dim dim);
+
 enum glsl_matrix_layout {
    /**
     * The layout of the matrix is inherited from the object containing the
@@ -260,6 +259,8 @@ enum {
 };
 
 #ifdef __cplusplus
+} /* extern "C" */
+
 #include "GL/gl.h"
 #include "util/ralloc.h"
 #include "main/menums.h" /* for gl_texture_index, C++'s enum rules are broken */