When deterministic feature will be enabled (turned-off by default) it'll guarantee deterministic

execution of wasm programs across different hardware/circumstances.
This is very useful for Blockchain projects having wasm smart-contracts

This is critical for Blockchain projects that require execution to be deterministic
in order to reach a consensus of the state transition of each smart-contract transaction.

Cargo.toml

@@ -26,7 +26,7 @@ wabt = "0.9.1"
 wasmer-clif-backend = { path = "lib/clif-backend" }
 wasmer-singlepass-backend = { path = "lib/singlepass-backend", optional = true }
 wasmer-middleware-common = { path = "lib/middleware-common" }
-wasmer-runtime = { path = "lib/runtime" }
+wasmer-runtime = { path = "lib/runtime", default-features = false }
 wasmer-runtime-core = { path = "lib/runtime-core" }
 wasmer-emscripten = { path = "lib/emscripten" }
 wasmer-llvm-backend = { path = "lib/llvm-backend", optional = true }
@@ -101,6 +101,8 @@ backend-singlepass = [
 wasi = ["wasmer-wasi"]
 managed = ["backend-singlepass", "wasmer-runtime-core/managed"]
 
+deterministic = ["wasmer-runtime/deterministic"]
+
 [[example]]
 name = "plugin"
 crate-type = ["bin"]

lib/runtime-core/Cargo.toml

@@ -58,3 +58,4 @@ trace = ["debug"]
 "backend-singlepass" = []
 "backend-llvm" = []
 managed = []
+deterministic = ["wasmparser/deterministic"]

lib/runtime-core/src/codegen.rs

@@ -145,6 +145,9 @@ pub fn validating_parser_config(features: &Features) -> wasmparser::ValidatingPa
             enable_simd: features.simd,
             enable_bulk_memory: false,
             enable_multi_value: false,
+
+            #[cfg(feature = "deterministic")]
+            deterministic_only: true,
         },
     }
 }

lib/runtime-core/src/lib.rs

@@ -145,6 +145,9 @@ pub fn validate_and_report_errors_with_features(
             enable_multi_value: false,
             enable_reference_types: false,
             enable_threads: features.threads,
+
+            #[cfg(feature = "deterministic")]
+            deterministic_only: true,
         },
     };
     let mut parser = wasmparser::ValidatingParser::new(wasm, Some(config));

lib/runtime/Cargo.toml

@@ -41,6 +41,7 @@ singlepass = ["wasmer-singlepass-backend"]
 default-backend-singlepass = ["singlepass"]
 default-backend-llvm = ["llvm"]
 default-backend-cranelift = ["cranelift"]
+deterministic = ["wasmer-singlepass-backend/deterministic"]
 
 [[bench]]
 name = "nginx"

lib/runtime/src/lib.rs

@@ -199,13 +199,15 @@ pub fn default_compiler() -> impl Compiler {
             feature = "default-backend-llvm",
             any(
                 feature = "default-backend-cranelift",
-                feature = "default-backend-singlepass"
+                feature = "default-backend-singlepass",
+                feature = "deterministic"
             )
         ),
         all(
             feature = "default-backend-cranelift",
-            feature = "default-backend-singlepass"
-        )
+            any(feature = "default-backend-singlepass", feature = "deterministic")
+        ),
+        all(feature = "default-backend-singlepass", feature = "deterministic")
     ))]
     compile_error!(
         "The `default-backend-X` features are mutually exclusive.  Please choose just one"
@@ -214,7 +216,7 @@ pub fn default_compiler() -> impl Compiler {
     #[cfg(feature = "default-backend-llvm")]
     use wasmer_llvm_backend::LLVMCompiler as DefaultCompiler;
 
-    #[cfg(feature = "default-backend-singlepass")]
+    #[cfg(any(feature = "default-backend-singlepass", feature = "deterministic"))]
     use wasmer_singlepass_backend::SinglePassCompiler as DefaultCompiler;
 
     #[cfg(feature = "default-backend-cranelift")]

lib/singlepass-backend/Cargo.toml

@@ -18,3 +18,7 @@ byteorder = "1.3"
 nix = "0.15"
 libc = "0.2.60"
 smallvec = "0.6"
+
+[features]
+default = []
+deterministic = ["wasmparser/deterministic", "wasmer-runtime-core/deterministic"]