Optimize C++ generated code for structures with many conditional fields

compiler/back_end/cpp/BUILD

@@ -389,6 +389,17 @@ emboss_cc_test(
     ],
 )
 
+emboss_cc_test(
+    name = "many_conditionals_benchmark",
+    srcs = [
+        "testcode/many_conditionals_benchmark.cc",
+    ],
+    deps = [
+        "//testdata:many_conditionals_emboss",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 # New golden test infrastructure
 py_library(
     name = "one_golden_test_lib",
@@ -536,6 +547,7 @@ cpp_golden_test(
 cpp_golden_test(
     name = "no_enum_traits_golden_test",
     emb_file = "//testdata:no_enum_traits.emb",
+    extra_args = ["--no-cc-enum-traits"],
     golden_file = "//testdata/golden_cpp:no_enum_traits.emb.h",
 )
 
@@ -598,3 +610,9 @@ cpp_golden_test(
     emb_file = "//testdata:imported_genfiles.emb",
     golden_file = "//testdata/golden_cpp:imported_genfiles.emb.h",
 )
+
+cpp_golden_test(
+    name = "many_conditionals_golden_test",
+    emb_file = "//testdata:many_conditionals.emb",
+    golden_file = "//testdata/golden_cpp:many_conditionals.emb.h",
+)

compiler/back_end/cpp/build_defs.bzl

@@ -47,14 +47,15 @@ def emboss_cc_test(name, copts = None, no_w_sign_compare = False, **kwargs):
         **kwargs
     )
 
-def cpp_golden_test(name, emb_file, golden_file, import_dirs = []):
+def cpp_golden_test(name, emb_file, golden_file, import_dirs = [], extra_args = []):
     """Defines a C++ golden file test.
 
     Args:
         name: The name of the test.
         emb_file: The .emb file to test.
         golden_file: The golden .h file.
         import_dirs: A list of import directories.
+        extra_args: A list of extra arguments to pass to the compiler.
     """
     py_test(
         name = name,
@@ -66,7 +67,7 @@ def cpp_golden_test(name, emb_file, golden_file, import_dirs = []):
             "$(location :emboss_codegen_cpp)",
             "$(location %s)" % emb_file,
             "$(location %s)" % golden_file,
-        ] + ["--import-dir=" + d for d in import_dirs],
+        ] + ["--import-dir=" + d for d in import_dirs] + extra_args,
         data = [
             "//compiler/front_end:emboss_front_end",
             ":emboss_codegen_cpp",

compiler/back_end/cpp/generated_code_templates

@@ -127,6 +127,7 @@ class Generic${name}View final {
   bool Ok() const {
     if (!IsComplete()) return false;
 ${parameter_ok_checks}
+${ok_subexpressions}
 ${field_ok_checks}
 ${requires_check}
     return true;
@@ -391,11 +392,53 @@ ${write_fields}
 // ** ok_method_test ** ////////////////////////////////////////////////////////
     // If we don't have enough information to determine whether ${field} is
     // present in the structure, then structure.Ok() should be false.
-    if (!has_${field}.Known()) return false;
-    // If ${field} is present, but not Ok(), then structure.Ok() should be
-    // false.  If ${field} is not present, it does not matter whether it is
-    // Ok().
-    if (has_${field}.ValueOrDefault() && !${field}.Ok()) return false;
+    {
+      const auto emboss_reserved_local_field_present = ${existence_condition};
+      if (!emboss_reserved_local_field_present.Known()) return false;
+      // If ${field} is present, but not Ok(), then structure.Ok() should be
+      // false.  If ${field} is not present, it does not matter whether it is
+      // Ok().
+      if (emboss_reserved_local_field_present.ValueOrDefault() && !${field}.Ok()) return false;
+    }
+
+
+// ** ok_method_switch_block ** ////////////////////////////////////////////////
+    // Check fields that depend on a common discriminant using a switch.
+    {
+${inner_scope_definitions}
+      const auto emboss_reserved_switch_discrim = ${discriminant};
+      if (!emboss_reserved_switch_discrim.Known()) return false;
+      switch (emboss_reserved_switch_discrim.ValueOrDefault()) {
+${switch_cases}
+      }
+    }
+
+
+// ** ok_method_switch_case ** /////////////////////////////////////////////////
+        case ${case_value}:
+          if (!${field}().Ok()) return false;
+          break;
+
+
+// ** ok_method_if_block ** ////////////////////////////////////////////////////
+    // Check fields that share a common condition.
+    {
+${inner_scope_definitions}
+      const auto emboss_reserved_cond = ${condition};
+      if (!emboss_reserved_cond.Known()) return false;
+      if (emboss_reserved_cond.ValueOrDefault()) {
+${field_checks}
+      }
+    }
+
+
+// ** ok_method_field_check ** /////////////////////////////////////////////////
+        if (!${field}().Ok()) return false;
+
+
+// ** ok_method_unconditional_check ** /////////////////////////////////////////
+    // Field is always present (condition is statically true).
+    if (!${field}().Ok()) return false;
 
 
 // ** equals_method_test ** ////////////////////////////////////////////////////