+static GLenum
+_image_format_class_to_glenum(enum image_format_class class)
+{
+ switch (class) {
+ case IMAGE_FORMAT_CLASS_NONE:
+ return GL_NONE;
+ case IMAGE_FORMAT_CLASS_1X8:
+ return GL_IMAGE_CLASS_1_X_8;
+ case IMAGE_FORMAT_CLASS_1X16:
+ return GL_IMAGE_CLASS_1_X_16;
+ case IMAGE_FORMAT_CLASS_1X32:
+ return GL_IMAGE_CLASS_1_X_32;
+ case IMAGE_FORMAT_CLASS_2X8:
+ return GL_IMAGE_CLASS_2_X_8;
+ case IMAGE_FORMAT_CLASS_2X16:
+ return GL_IMAGE_CLASS_2_X_16;
+ case IMAGE_FORMAT_CLASS_2X32:
+ return GL_IMAGE_CLASS_2_X_32;
+ case IMAGE_FORMAT_CLASS_10_11_11:
+ return GL_IMAGE_CLASS_11_11_10;
+ case IMAGE_FORMAT_CLASS_4X8:
+ return GL_IMAGE_CLASS_4_X_8;
+ case IMAGE_FORMAT_CLASS_4X16:
+ return GL_IMAGE_CLASS_4_X_16;
+ case IMAGE_FORMAT_CLASS_4X32:
+ return GL_IMAGE_CLASS_4_X_32;
+ case IMAGE_FORMAT_CLASS_2_10_10_10:
+ return GL_IMAGE_CLASS_10_10_10_2;
+ default:
+ assert(!"Invalid image_format_class");
+ return GL_NONE;
+ }
+}
+
+GLenum
+_mesa_get_image_format_class(GLenum format)
+{
+ mesa_format tex_format = _mesa_get_shader_image_format(format);
+ if (tex_format == MESA_FORMAT_NONE)
+ return GL_NONE;
+
+ enum image_format_class class = get_image_format_class(tex_format);
+ return _image_format_class_to_glenum(class);
+}
+
+bool
+_mesa_is_shader_image_format_supported(const struct gl_context *ctx,
+ GLenum format)
+{
+ switch (format) {
+ /* Formats supported on both desktop and ES GL, c.f. table 8.27 of the
+ * OpenGL ES 3.1 specification.
+ */
+ case GL_RGBA32F:
+ case GL_RGBA16F:
+ case GL_R32F:
+ case GL_RGBA32UI:
+ case GL_RGBA16UI:
+ case GL_RGBA8UI:
+ case GL_R32UI:
+ case GL_RGBA32I:
+ case GL_RGBA16I:
+ case GL_RGBA8I:
+ case GL_R32I:
+ case GL_RGBA8:
+ case GL_RGBA8_SNORM:
+ return true;
+
+ /* Formats supported on unextended desktop GL and the original
+ * ARB_shader_image_load_store extension, c.f. table 3.21 of the OpenGL 4.2
+ * specification or by GLES 3.1 with GL_NV_image_formats extension.
+ */
+ case GL_RG32F:
+ case GL_RG16F:
+ case GL_R11F_G11F_B10F:
+ case GL_R16F:
+ case GL_RGB10_A2UI:
+ case GL_RG32UI:
+ case GL_RG16UI:
+ case GL_RG8UI:
+ case GL_R16UI:
+ case GL_R8UI:
+ case GL_RG32I:
+ case GL_RG16I:
+ case GL_RG8I:
+ case GL_R16I:
+ case GL_R8I:
+ case GL_RGB10_A2:
+ case GL_RG8:
+ case GL_R8:
+ case GL_RG8_SNORM:
+ case GL_R8_SNORM:
+ return true;
+
+ /* Formats supported on unextended desktop GL and the original
+ * ARB_shader_image_load_store extension, c.f. table 3.21 of the OpenGL 4.2
+ * specification.
+ *
+ * These can be supported by GLES 3.1 with GL_NV_image_formats &
+ * GL_EXT_texture_norm16 extensions but we don't have support for the
+ * latter in Mesa yet.
+ */
+ case GL_RGBA16:
+ case GL_RGBA16_SNORM:
+ case GL_RG16:
+ case GL_RG16_SNORM:
+ case GL_R16:
+ case GL_R16_SNORM:
+ return _mesa_is_desktop_gl(ctx);
+
+ default:
+ return false;
+ }
+}
+
+struct gl_image_unit
+_mesa_default_image_unit(struct gl_context *ctx)
+{
+ const GLenum format = _mesa_is_desktop_gl(ctx) ? GL_R8 : GL_R32UI;
+ const struct gl_image_unit u = {
+ .Access = GL_READ_ONLY,
+ .Format = format,
+ ._ActualFormat = _mesa_get_shader_image_format(format)
+ };
+ return u;
+}
+