Fix wasmer binary

lib/runtime/src/lib.rs

@@ -164,14 +164,27 @@ pub enum Backend {
 }
 
 impl Backend {
+    /// Get a list of the currently enabled (via feature flag) backends.
+    pub fn variants() -> &'static [&'static str] {
+        &[
+            #[cfg(feature = "singlepass")]
+            "singlepass",
+            #[cfg(feature = "cranelift")]
+            "cranelift",
+            #[cfg(feature = "llvm")]
+            "llvm",
+            "auto",
+        ]
+    }
+
     /// 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 = "cranelift")]
+            Backend::Cranelift => "cranelift",
             #[cfg(feature = "llvm")]
             Backend::LLVM => "llvm",
             Backend::Auto => "auto",
@@ -192,6 +205,22 @@ impl Default for Backend {
     }
 }
 
+impl std::str::FromStr for Backend {
+    type Err = String;
+    fn from_str(s: &str) -> Result<Backend, String> {
+        match s.to_lowercase().as_str() {
+            #[cfg(feature = "singlepass")]
+            "singlepass" => Ok(Backend::Singlepass),
+            #[cfg(feature = "cranelift")]
+            "cranelift" => Ok(Backend::Cranelift),
+            #[cfg(feature = "llvm")]
+            "llvm" => Ok(Backend::LLVM),
+            "auto" => Ok(Backend::Auto),
+            _ => Err(format!("The backend {} doesn't exist", s)),
+        }
+    }
+}
+
 /// Compile WebAssembly binary code into a [`Module`].
 /// This function is useful if it is necessary to
 /// compile a module before it can be instantiated

src/bin/wasmer.rs

@@ -30,13 +30,13 @@ use wasmer_llvm_backend::{
 };
 use wasmer_runtime::{
     cache::{Cache as BaseCache, FileSystemCache, WasmHash},
-    Value, VERSION,
+    Backend, Value, VERSION,
 };
 #[cfg(feature = "managed")]
 use wasmer_runtime_core::tiering::{run_tiering, InteractiveShellContext, ShellExitOperation};
 use wasmer_runtime_core::{
     self,
-    backend::{Backend, Compiler, CompilerConfig, Features, MemoryBoundCheckMode},
+    backend::{Compiler, CompilerConfig, Features, MemoryBoundCheckMode},
     debug,
     loader::{Instance as LoadedInstance, LocalLoader},
     Module,
@@ -143,7 +143,7 @@ struct Run {
     #[structopt(parse(from_os_str))]
     path: PathBuf,
 
-    /// Name of the backend to use. (x86_64)
+    /// Name of the backend to use (x86_64)
     #[cfg(target_arch = "x86_64")]
     #[structopt(
         long = "backend",
@@ -153,7 +153,7 @@ struct Run {
     )]
     backend: Backend,
 
-    /// Name of the backend to use. (aarch64)
+    /// Name of the backend to use (aarch64)
     #[cfg(target_arch = "aarch64")]
     #[structopt(
         long = "backend",
@@ -486,7 +486,7 @@ fn execute_wasi(
                 baseline: true,
                 msm: msm,
                 base: instance.module.runnable_module.get_code().unwrap().as_ptr() as usize,
-                backend: options.backend,
+                backend: options.backend.to_string().to_owned(),
                 runnable_module: instance.module.runnable_module.clone(),
             });
             true
@@ -618,8 +618,15 @@ fn execute_wasm(options: &Run) -> Result<(), String> {
     };
 
     // Don't error on --enable-all for other backends.
-    if options.features.simd && options.backend != Backend::LLVM {
-        return Err("SIMD is only supported in the LLVM backend for now".to_string());
+    if options.features.simd {
+        #[cfg(feature = "backend-llvm")]
+        {
+            if options.backend != Backend::LLVM {
+                return Err("SIMD is only supported in the LLVM backend for now".to_string());
+            }
+        }
+        #[cfg(not(feature = "backend-llvm"))]
+        return Err("SIMD is not supported in this backend".to_string());
     }
 
     if !utils::is_wasm_binary(&wasm_binary) {
@@ -1031,16 +1038,10 @@ fn get_compiler_by_backend(backend: Backend, _opts: &Run) -> Option<Box<dyn Comp
                 StreamingCompiler::new(middlewares_gen);
             Box::new(c)
         }
-        #[cfg(not(feature = "backend-singlepass"))]
-        Backend::Singlepass => return None,
         #[cfg(feature = "backend-cranelift")]
         Backend::Cranelift => Box::new(CraneliftCompiler::new()),
-        #[cfg(not(feature = "backend-cranelift"))]
-        Backend::Cranelift => return None,
         #[cfg(feature = "backend-llvm")]
         Backend::LLVM => Box::new(LLVMCompiler::new()),
-        #[cfg(not(feature = "backend-llvm"))]
-        Backend::LLVM => return None,
         Backend::Auto => return None,
     })
 }