[meta] Small fixes in the settings generation;

cranelift/codegen/meta/src/isa/riscv/mod.rs

@@ -41,7 +41,7 @@ fn define_settings(shared: &SettingGroup) -> SettingGroup {
     setting.add_bool(
         "enable_e",
         "Enable the 'RV32E' instruction set with only 16 registers",
-        true,
+        false,
     );
 
     let shared_enable_atomics = shared.get_bool("enable_atomics");

cranelift/codegen/meta/src/isa/x86/mod.rs

@@ -65,6 +65,8 @@ fn define_settings(shared: &SettingGroup) -> SettingGroup {
         predicate!(!allones_funcaddrs && !is_pic),
     );
 
+    // Presets corresponding to x86 CPUs.
+
     settings.add_preset("baseline", preset!());
     let nehalem = settings.add_preset(
         "nehalem",