Remove Backend dependency

Cargo.lock

@@ -1752,6 +1752,8 @@ dependencies = [
  "criterion",
  "lazy_static",
  "memmap",
+ "serde",
+ "serde_derive",
  "tempfile",
  "wabt",
  "wasmer-clif-backend",

lib/clif-backend/src/code.rs

@@ -18,7 +18,7 @@ use std::mem;
 use std::sync::{Arc, RwLock};
 use wasmer_runtime_core::error::CompileError;
 use wasmer_runtime_core::{
-    backend::{Backend, CacheGen, Token},
+    backend::{CacheGen, Token},
     cache::{Artifact, Error as CacheError},
     codegen::*,
     memory::MemoryType,
@@ -58,8 +58,8 @@ impl ModuleCodeGenerator<CraneliftFunctionCodeGenerator, Caller, CodegenError>
         unimplemented!("cross compilation is not available for clif backend")
     }
 
-    fn backend_id() -> Backend {
+    fn backend_id() -> String {
-        Backend::Cranelift
+        "cranelift".to_string()
     }
 
     fn check_precondition(&mut self, _module_info: &ModuleInfo) -> Result<(), CodegenError> {

lib/llvm-backend/src/code.rs

@@ -8721,8 +8721,8 @@ impl<'ctx> ModuleCodeGenerator<LLVMFunctionCodeGenerator<'ctx>, LLVMBackend, Cod
         }
     }
 
-    fn backend_id() -> Backend {
+    fn backend_id() -> String {
-        Backend::LLVM
+        "llvm".to_string()
     }
 
     fn check_precondition(&mut self, _module_info: &ModuleInfo) -> Result<(), CodegenError> {

lib/middleware-common-tests/src/lib.rs

@@ -8,40 +8,40 @@ mod tests {
     use wasmer_runtime_core::fault::{pop_code_version, push_code_version};
     use wasmer_runtime_core::state::CodeVersion;
     use wasmer_runtime_core::{
-        backend::{Backend, Compiler},
+        backend::Compiler,
         compile_with, imports, Func,
     };
 
     #[cfg(feature = "llvm")]
-    fn get_compiler(limit: u64) -> (impl Compiler, Backend) {
+    fn get_compiler(limit: u64) -> impl Compiler {
         use wasmer_llvm_backend::ModuleCodeGenerator as LLVMMCG;
         let c: StreamingCompiler<LLVMMCG, _, _, _, _> = StreamingCompiler::new(move || {
             let mut chain = MiddlewareChain::new();
             chain.push(Metering::new(limit));
             chain
         });
-        (c, Backend::LLVM)
+        c
     }
 
     #[cfg(feature = "singlepass")]
-    fn get_compiler(limit: u64) -> (impl Compiler, Backend) {
+    fn get_compiler(limit: u64) -> impl Compiler {
         use wasmer_singlepass_backend::ModuleCodeGenerator as SinglePassMCG;
         let c: StreamingCompiler<SinglePassMCG, _, _, _, _> = StreamingCompiler::new(move || {
             let mut chain = MiddlewareChain::new();
             chain.push(Metering::new(limit));
             chain
         });
-        (c, Backend::Singlepass)
+        c
     }
 
     #[cfg(not(any(feature = "llvm", feature = "clif", feature = "singlepass")))]
     compile_error!("compiler not specified, activate a compiler via features");
 
     #[cfg(feature = "clif")]
-    fn get_compiler(_limit: u64) -> (impl Compiler, Backend) {
+    fn get_compiler(_limit: u64) -> impl Compiler {
         compile_error!("cranelift does not implement metering");
         use wasmer_clif_backend::CraneliftCompiler;
-        (CraneliftCompiler::new(), Backend::Cranelift)
+        CraneliftCompiler::new()
     }
 
     // Assemblyscript
@@ -161,7 +161,12 @@ mod tests {
 
         let add_to: Func<(i32, i32), i32> = instance.func("add_to").unwrap();
 
-        let cv_pushed = if let Some(msm) = instance.module.runnable_module.get_module_state_map() {
+        let cv_pushed = if let Some(msm) = instance
+            .module
+            .runnable_module
+            .borrow()
+            .get_module_state_map()
+        {
             push_code_version(CodeVersion {
                 baseline: true,
                 msm: msm,

lib/runtime-core/src/cache.rs

@@ -3,12 +3,11 @@
 //! and loaded to allow skipping compilation and fast startup.
 
 use crate::{
-    backend::Backend,
+    module::ModuleInfo,
-    module::{Module, ModuleInfo},
     sys::Memory,
 };
 use blake2b_simd::blake2bp;
-use std::{fmt, io, mem, slice};
+use std::{io, mem, slice};
 
 /// Indicates the invalid type of invalid cache file
 #[derive(Debug)]
@@ -35,7 +34,7 @@ pub enum Error {
     /// The cached binary has been invalidated.
     InvalidatedCache,
     /// The current backend does not support caching.
-    UnsupportedBackend(Backend),
+    UnsupportedBackend(String),
 }
 
 impl From<io::Error> for Error {
@@ -246,24 +245,6 @@ impl Artifact {
     }
 }
 
-/// A generic cache for storing and loading compiled wasm modules.
-///
-/// The `wasmer-runtime` supplies a naive `FileSystemCache` api.
-pub trait Cache {
-    /// Error type to return when load error occurs
-    type LoadError: fmt::Debug;
-    /// Error type to return when store error occurs
-    type StoreError: fmt::Debug;
-
-    /// loads a module using the default `Backend`
-    fn load(&self, key: WasmHash) -> Result<Module, Self::LoadError>;
-    /// loads a cached module using a specific `Backend`
-    fn load_with_backend(&self, key: WasmHash, backend: Backend)
-        -> Result<Module, Self::LoadError>;
-    /// Store a module into the cache with the given key
-    fn store(&mut self, key: WasmHash, module: Module) -> Result<(), Self::StoreError>;
-}
-
 /// A unique ID generated from the version of Wasmer for use with cache versioning
 pub const WASMER_VERSION_HASH: &'static str =
     include_str!(concat!(env!("OUT_DIR"), "/wasmer_version_hash.txt"));

lib/runtime-core/src/codegen.rs

@@ -92,10 +92,10 @@ pub trait ModuleCodeGenerator<FCG: FunctionCodeGenerator<E>, RM: RunnableModule,
     ) -> Self;
 
     /// Returns the backend id associated with this MCG.
-    fn backend_id() -> Backend;
+    fn backend_id() -> String;
 
     /// It sets if the current compiler requires validation before compilation
-    fn requires_pre_validation(&self) -> bool {
+    fn requires_pre_validation() -> bool {
         true
     }
 
@@ -231,8 +231,8 @@ impl<
             validate_with_features(wasm, &compiler_config.features)?;
         }
 
-        let mut mcg = match MCG::backend_id() {
+        let mut mcg = match MCG::backend_id().as_ref() {
-            Backend::LLVM => MCG::new_with_target(
+            "llvm" => MCG::new_with_target(
                 compiler_config.triple.clone(),
                 compiler_config.cpu_name.clone(),
                 compiler_config.cpu_features.clone(),
@@ -242,7 +242,6 @@ impl<
         let mut chain = (self.middleware_chain_generator)();
         let info = crate::parse::read_module(
             wasm,
-            MCG::backend_id(),
             &mut mcg,
             &mut chain,
             &compiler_config,

lib/runtime-core/src/module.rs

@@ -1,7 +1,7 @@
 //! The module module contains the implementation data structures and helper functions used to
 //! manipulate and access wasm modules.
 use crate::{
-    backend::{Backend, RunnableModule},
+    backend::RunnableModule,
     cache::{Artifact, Error as CacheError},
     error,
     import::ImportObject,
@@ -65,7 +65,7 @@ pub struct ModuleInfo {
     /// Map signature index to function signature.
     pub signatures: Map<SigIndex, FuncSig>,
     /// Backend.
-    pub backend: Backend,
+    pub backend: String,
 
     /// Table of namespace indexes.
     pub namespace_table: StringTable<NamespaceIndex>,

lib/runtime-core/src/parse.rs

@@ -3,7 +3,7 @@
 
 use crate::codegen::*;
 use crate::{
-    backend::{Backend, CompilerConfig, RunnableModule},
+    backend::{CompilerConfig, RunnableModule},
     error::CompileError,
     module::{
         DataInitializer, ExportIndex, ImportName, ModuleInfo, StringTable, StringTableBuilder,
@@ -57,7 +57,6 @@ pub fn read_module<
     E: Debug,
 >(
     wasm: &[u8],
-    backend: Backend,
     mcg: &mut MCG,
     middlewares: &mut MiddlewareChain,
     compiler_config: &CompilerConfig,
@@ -83,7 +82,7 @@ pub fn read_module<
 
         func_assoc: Map::new(),
         signatures: Map::new(),
-        backend: backend,
+        backend: MCG::backend_id(),
 
         namespace_table: StringTable::new(),
         name_table: StringTable::new(),

lib/runtime-core/src/state.rs

@@ -2,7 +2,7 @@
 //! state could read or updated at runtime. Use cases include generating stack traces, switching
 //! generated code from one tier to another, or serializing state of a running instace.
 
-use crate::backend::{Backend, RunnableModule};
+use crate::backend::RunnableModule;
 use std::collections::BTreeMap;
 use std::ops::Bound::{Included, Unbounded};
 use std::sync::Arc;
@@ -186,7 +186,7 @@ pub struct CodeVersion {
     pub base: usize,
 
     /// The backend used to compile this module.
-    pub backend: Backend,
+    pub backend: String,
 
     /// `RunnableModule` for this code version.
     pub runnable_module: Arc<Box<dyn RunnableModule>>,

lib/runtime-core/src/tiering.rs

@@ -1,6 +1,6 @@
 //! The tiering module supports switching between code compiled with different optimization levels
 //! as runtime.
-use crate::backend::{Backend, Compiler, CompilerConfig};
+use crate::backend::{Compiler, CompilerConfig};
 use crate::compile_with_config;
 use crate::fault::{
     catch_unsafe_unwind, ensure_sighandler, pop_code_version, push_code_version, with_ctx,
@@ -43,7 +43,7 @@ struct OptimizationState {
 }
 
 struct OptimizationOutcome {
-    backend_id: Backend,
+    backend_id: String,
     module: Module,
 }
 
@@ -54,7 +54,7 @@ unsafe impl Sync for CtxWrapper {}
 
 unsafe fn do_optimize(
     binary: &[u8],
-    backend_id: Backend,
+    backend_id: String,
     compiler: Box<dyn Compiler>,
     ctx: &Mutex<CtxWrapper>,
     state: &OptimizationState,
@@ -87,8 +87,8 @@ pub unsafe fn run_tiering<F: Fn(InteractiveShellContext) -> ShellExitOperation>(
     import_object: &ImportObject,
     start_raw: extern "C" fn(&mut Ctx),
     baseline: &mut Instance,
-    baseline_backend: Backend,
+    baseline_backend: String,
-    optimized_backends: Vec<(Backend, Box<dyn Fn() -> Box<dyn Compiler> + Send>)>,
+    optimized_backends: Vec<(String, Box<dyn Fn() -> Box<dyn Compiler> + Send>)>,
     interactive_shell: F,
 ) -> Result<(), String> {
     ensure_sighandler();
@@ -140,7 +140,7 @@ pub unsafe fn run_tiering<F: Fn(InteractiveShellContext) -> ShellExitOperation>(
     }));
 
     loop {
-        let new_optimized: Option<(Backend, &mut Instance)> = {
+        let new_optimized: Option<(String, &mut Instance)> = {
             let mut outcome = opt_state.outcome.lock().unwrap();
             if let Some(x) = outcome.take() {
                 let instance = x

lib/runtime-core/src/vm.rs

@@ -1064,7 +1064,7 @@ mod vm_ctx_tests {
 
     fn generate_module() -> ModuleInner {
         use super::Func;
-        use crate::backend::{sys::Memory, Backend, CacheGen, RunnableModule};
+        use crate::backend::{sys::Memory, CacheGen, RunnableModule};
         use crate::cache::Error as CacheError;
         use crate::typed_func::Wasm;
         use crate::types::{LocalFuncIndex, SigIndex};
@@ -1118,7 +1118,7 @@ mod vm_ctx_tests {
 
                 func_assoc: Map::new(),
                 signatures: Map::new(),
-                backend: Backend::Cranelift,
+                backend: "".to_string(),
 
                 namespace_table: StringTable::new(),
                 name_table: StringTable::new(),

lib/runtime/Cargo.toml

@@ -24,6 +24,14 @@ path = "../clif-backend"
 version = "0.12.0"
 optional = true
 
+# Dependencies for caching.
+[dependencies.serde]
+version = "1.0"
+# This feature is required for serde to support serializing/deserializing reference counted pointers (e.g. Rc and Arc).
+features = ["rc"]
+[dependencies.serde_derive]
+version = "1.0"
+
 [dev-dependencies]
 tempfile = "3.1"
 criterion = "0.2"

lib/runtime/src/cache.rs

@@ -5,6 +5,7 @@
 use crate::Module;
 use memmap::Mmap;
 use std::{
+    fmt,
     fs::{create_dir_all, File},
     io::{self, Write},
     path::PathBuf,
@@ -12,9 +13,27 @@ use std::{
 
 use wasmer_runtime_core::cache::Error as CacheError;
 pub use wasmer_runtime_core::{
-    backend::Backend,
+    cache::{Artifact, WasmHash},
-    cache::{Artifact, Cache, WasmHash},
 };
+pub use super::Backend;
+
+/// A generic cache for storing and loading compiled wasm modules.
+///
+/// The `wasmer-runtime` supplies a naive `FileSystemCache` api.
+pub trait Cache {
+    /// Error type to return when load error occurs
+    type LoadError: fmt::Debug;
+    /// Error type to return when store error occurs
+    type StoreError: fmt::Debug;
+
+    /// loads a module using the default `Backend`
+    fn load(&self, key: WasmHash) -> Result<Module, Self::LoadError>;
+    /// loads a cached module using a specific `Backend`
+    fn load_with_backend(&self, key: WasmHash, backend: Backend)
+        -> Result<Module, Self::LoadError>;
+    /// Store a module into the cache with the given key
+    fn store(&mut self, key: WasmHash, module: Module) -> Result<(), Self::StoreError>;
+}
 
 /// Representation of a directory that contains compiled wasm artifacts.
 ///
@@ -105,7 +124,7 @@ impl Cache for FileSystemCache {
             wasmer_runtime_core::load_cache_with(
                 serialized_cache,
                 crate::compiler_for_backend(backend)
-                    .ok_or_else(|| CacheError::UnsupportedBackend(backend))?
+                    .ok_or_else(|| CacheError::UnsupportedBackend(backend.to_string().to_owned()))?
                     .as_ref(),
             )
         }

lib/runtime/src/lib.rs

@@ -91,7 +91,10 @@
 //! [`wasmer-singlepass-backend`]: https://crates.io/crates/wasmer-singlepass-backend
 //! [`wasmer-clif-backend`]: https://crates.io/crates/wasmer-clif-backend
 
-pub use wasmer_runtime_core::backend::{Backend, Features};
+#[macro_use]
+extern crate serde_derive;
+
+pub use wasmer_runtime_core::backend::Features;
 pub use wasmer_runtime_core::codegen::{MiddlewareChain, StreamingCompiler};
 pub use wasmer_runtime_core::export::Export;
 pub use wasmer_runtime_core::global::Global;
@@ -144,6 +147,52 @@ pub mod cache;
 
 pub use wasmer_runtime_core::backend::{Compiler, CompilerConfig};
 
+/// Enum used to select which compiler should be used to generate code.
+#[derive(Serialize, Deserialize, Debug, Copy, Clone, PartialEq, Eq)]
+pub enum Backend {
+    #[cfg(feature = "singlepass")]
+    /// Singlepass backend
+    Singlepass,
+    #[cfg(feature = "cranelift")]
+    /// Cranelift backend
+    Cranelift,
+    #[cfg(feature = "llvm")]
+    /// LLVM backend
+    LLVM,
+    /// Auto backend
+    Auto,
+}
+
+impl Backend {
+    /// Stable string representation of the backend.
+    /// It can be used as part of a cache key, for example.
+    pub fn to_string(&self) -> &'static str {
+        match self {
+            #[cfg(feature = "cranelift")]
+            Backend::Cranelift => "cranelift",
+            #[cfg(feature = "singlepass")]
+            Backend::Singlepass => "singlepass",
+            #[cfg(feature = "llvm")]
+            Backend::LLVM => "llvm",
+            Backend::Auto => "auto",
+        }
+    }
+}
+
+impl Default for Backend {
+    fn default() -> Self {
+        #[cfg(all(feature = "default-backend-singlepass", not(feature = "docs")))]
+        return Backend::Singlepass;
+    
+        #[cfg(any(feature = "default-backend-cranelift", feature = "docs"))]
+        return Backend::Cranelift;
+
+        #[cfg(all(feature = "default-backend-llvm", not(feature = "docs")))]
+        return Backend::LLVM;
+    }
+}
+
+
 /// Compile WebAssembly binary code into a [`Module`].
 /// This function is useful if it is necessary to
 /// compile a module before it can be instantiated
@@ -268,9 +317,6 @@ pub fn compiler_for_backend(backend: Backend) -> Option<Box<dyn Compiler>> {
             #[cfg(feature = "default-backend-llvm")]
             return Some(Box::new(wasmer_llvm_backend::LLVMCompiler::new()));
         }
-
-        #[cfg(not(all(feature = "llvm", feature = "singlepass", feature = "cranelift")))]
-        _ => None,
     }
 }
 

lib/singlepass-backend/src/codegen_x64.rs

@@ -23,7 +23,7 @@ use std::{
 use wasmer_runtime_core::{
     backend::{
         sys::{Memory, Protect},
-        Architecture, Backend, CacheGen, CompilerConfig, InlineBreakpoint, InlineBreakpointType,
+        Architecture, CacheGen, CompilerConfig, InlineBreakpoint, InlineBreakpointType,
         MemoryBoundCheckMode, RunnableModule, Token,
     },
     cache::{Artifact, Error as CacheError},
@@ -647,10 +647,14 @@ impl ModuleCodeGenerator<X64FunctionCode, X64ExecutionContext, CodegenError>
     }
 
     /// Singlepass does validation as it compiles
-    fn requires_pre_validation(&self) -> bool {
+    fn requires_pre_validation() -> bool {
         false
     }
 
+    fn backend_id() -> String {
+        "singlepass".to_string()
+    }
+
     fn new_with_target(_: Option<String>, _: Option<String>, _: Option<String>) -> Self {
         unimplemented!("cross compilation is not available for singlepass backend")
     }