Add env var for experiments

aptos-move/aptos-vm-environment/src/environment.rs

@@ -15,7 +15,8 @@ use aptos_native_interface::SafeNativeBuilder;
 use aptos_types::{
     chain_id::ChainId,
     on_chain_config::{
-        ConfigurationResource, Features, OnChainConfig, TimedFeatures, TimedFeaturesBuilder,
+        ConfigurationResource, FeatureFlag, Features, OnChainConfig, TimedFeatures,
+        TimedFeaturesBuilder,
     },
     state_store::StateView,
 };
@@ -175,8 +176,13 @@ impl Environment {
     ) -> Self {
         // We compute and store a hash of configs in order to distinguish different environments.
         let mut sha3_256 = Sha3_256::new();
-        let features =
+        let mut features =
             fetch_config_and_update_hash::<Features>(&mut sha3_256, state_view).unwrap_or_default();
+        if std::env::var("USE_LOADER_V1").is_ok() {
+            features.disable(FeatureFlag::ENABLE_LOADER_V2);
+        } else {
+            features.enable(FeatureFlag::ENABLE_LOADER_V2);
+        }
 
         // If no chain ID is in storage, we assume we are in a testing environment.
         let chain_id = fetch_config_and_update_hash::<ChainId>(&mut sha3_256, state_view)

third_party/move/move-vm/runtime/src/config.rs

@@ -44,7 +44,7 @@ impl Default for VMConfig {
             ty_builder: TypeBuilder::with_limits(128, 20),
             disallow_dispatch_for_native: true,
             use_compatibility_checker_v2: true,
-            use_loader_v2: true,
+            use_loader_v2: std::env::var("USE_LOADER_V1").is_err(),
         }
     }
 }

types/src/on_chain_config/aptos_features.rs

@@ -195,6 +195,11 @@ impl Default for Features {
         for feature in FeatureFlag::default_features() {
             features.enable(feature);
         }
+        if std::env::var("USE_LOADER_V1").is_ok() {
+            features.disable(FeatureFlag::ENABLE_LOADER_V2);
+        } else {
+            features.enable(FeatureFlag::ENABLE_LOADER_V2);
+        }
         features
     }
 }