review follow-up:

* reorder enum and lists from largest to smallest cell type
* add utilities for listing stable and ustable cell types
  (with simple test)

3 files changed, 27 insertions, 3 deletions

diff --git a/eval/src/tests/eval/value_type/value_type_test.cpp b/eval/src/tests/eval/value_type/value_type_test.cpp
index 554cfba8c94..a2b25a12b4b 100644
--- a/eval/src/tests/eval/value_type/value_type_test.cpp
+++ b/eval/src/tests/eval/value_type/value_type_test.cpp
@@ -572,12 +572,22 @@ TEST("require that cell array size can be calculated") {
 }
 
 TEST("require that all cell types can be listed") {
-    std::vector<CellType> expect = { CellType::INT8, CellType::BFLOAT16, CellType::FLOAT, CellType::DOUBLE };
+    std::vector<CellType> expect = { CellType::DOUBLE, CellType::FLOAT, CellType::BFLOAT16, CellType::INT8 };
+    std::vector<CellType> expect_stable;
+    std::vector<CellType> expect_unstable;
     auto list = CellTypeUtils::list_types();
     ASSERT_EQUAL(list.size(), expect.size());
     for (size_t i = 0; i < list.size(); ++i) {
         EXPECT_TRUE(list[i] == expect[i]);
+        CellMeta cm(expect[i], false);
+        if (cm.decay().eq(cm)) {
+            expect_stable.push_back(cm.cell_type);
+        } else {
+            expect_unstable.push_back(cm.cell_type);
+        }
     }
+    EXPECT_TRUE(expect_stable == CellTypeUtils::list_stable_types());
+    EXPECT_TRUE(expect_unstable == CellTypeUtils::list_unstable_types());
 }
 
 TEST_MAIN() { TEST_RUN_ALL(); }
diff --git a/eval/src/vespa/eval/eval/cell_type.cpp b/eval/src/vespa/eval/eval/cell_type.cpp
index 95bbecaa6ee..94bd0b14573 100644
--- a/eval/src/vespa/eval/eval/cell_type.cpp
+++ b/eval/src/vespa/eval/eval/cell_type.cpp
@@ -33,7 +33,19 @@ CellTypeUtils::mem_size(CellType cell_type, size_t sz)
 std::vector<CellType>
 CellTypeUtils::list_types()
 {
-    return {CellType::INT8, CellType::BFLOAT16, CellType::FLOAT, CellType::DOUBLE};
+    return {CellType::DOUBLE, CellType::FLOAT, CellType::BFLOAT16, CellType::INT8 };
+}
+
+std::vector<CellType>
+CellTypeUtils::list_stable_types()
+{
+    return {CellType::DOUBLE, CellType::FLOAT};
+}
+
+std::vector<CellType>
+CellTypeUtils::list_unstable_types()
+{
+    return {CellType::BFLOAT16, CellType::INT8 };
 }
 
 }
diff --git a/eval/src/vespa/eval/eval/cell_type.h b/eval/src/vespa/eval/eval/cell_type.h
index 02e321ac744..79750c5c875 100644
--- a/eval/src/vespa/eval/eval/cell_type.h
+++ b/eval/src/vespa/eval/eval/cell_type.h
@@ -11,7 +11,7 @@
 
 namespace vespalib::eval {
 
-enum class CellType : char { FLOAT, DOUBLE, BFLOAT16, INT8 };
+enum class CellType : char { DOUBLE, FLOAT, BFLOAT16, INT8 };
 
 // converts actual cell type to CellType enum value
 template <typename CT> constexpr CellType get_cell_type();
@@ -199,6 +199,8 @@ struct CellTypeUtils {
     static uint32_t alignment(CellType cell_type);
     static size_t mem_size(CellType cell_type, size_t sz);
     static std::vector<CellType> list_types();
+    static std::vector<CellType> list_stable_types();
+    static std::vector<CellType> list_unstable_types();
 };
 
 } // namespace