Move backend_id to static str

lib/clif-backend/src/code.rs

@@ -32,6 +32,8 @@ use wasmer_runtime_core::{
 };
 use wasmparser::Type as WpType;
 
+static BACKEND_ID: &str = "cranelift";
+
 pub struct CraneliftModuleCodeGenerator {
     isa: Box<dyn isa::TargetIsa>,
     signatures: Option<Arc<Map<SigIndex, FuncSig>>>,
@@ -58,8 +60,8 @@ impl ModuleCodeGenerator<CraneliftFunctionCodeGenerator, Caller, CodegenError>
         unimplemented!("cross compilation is not available for clif backend")
     }
 
-    fn backend_id() -> String {
-        "cranelift".to_string()
+    fn backend_id() -> &'static str {
+        BACKEND_ID
     }
 
     fn check_precondition(&mut self, _module_info: &ModuleInfo) -> Result<(), CodegenError> {

lib/llvm-backend/src/code.rs

@@ -45,6 +45,8 @@ use wasmer_runtime_core::{
 };
 use wasmparser::{BinaryReaderError, MemoryImmediate, Operator, Type as WpType};
 
+static BACKEND_ID: &str = "llvm";
+
 fn func_sig_to_llvm<'ctx>(
     context: &'ctx Context,
     intrinsics: &Intrinsics<'ctx>,
@@ -8721,8 +8723,8 @@ impl<'ctx> ModuleCodeGenerator<LLVMFunctionCodeGenerator<'ctx>, LLVMBackend, Cod
         }
     }
 
-    fn backend_id() -> String {
-        "llvm".to_string()
+    fn backend_id() -> &'static str {
+        BACKEND_ID
     }
 
     fn check_precondition(&mut self, _module_info: &ModuleInfo) -> Result<(), CodegenError> {

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

@@ -110,7 +110,7 @@ mod tests {
                 baseline: true,
                 msm: msm,
                 base: instance.module.runnable_module.get_code().unwrap().as_ptr() as usize,
-                backend: MCG::backend_id(),
+                backend: MCG::backend_id().to_string(),
                 runnable_module: instance.module.runnable_module.clone(),
             });
             true
@@ -152,7 +152,7 @@ mod tests {
                 baseline: true,
                 msm: msm,
                 base: instance.module.runnable_module.get_code().unwrap().as_ptr() as usize,
-                backend: MCG::backend_id(),
+                backend: MCG::backend_id().to_string(),
                 runnable_module: instance.module.runnable_module.clone(),
             });
             true

lib/runtime-core/src/codegen.rs

@@ -92,7 +92,7 @@ pub trait ModuleCodeGenerator<FCG: FunctionCodeGenerator<E>, RM: RunnableModule,
     ) -> Self;
 
     /// Returns the backend id associated with this MCG.
-    fn backend_id() -> String;
+    fn backend_id() -> &'static str;
 
     /// It sets if the current compiler requires validation before compilation
     fn requires_pre_validation() -> bool {
@@ -231,7 +231,7 @@ impl<
             validate_with_features(wasm, &compiler_config.features)?;
         }
 
-        let mut mcg = match MCG::backend_id().as_ref() {
+        let mut mcg = match MCG::backend_id() {
             "llvm" => MCG::new_with_target(
                 compiler_config.triple.clone(),
                 compiler_config.cpu_name.clone(),

lib/runtime-core/src/parse.rs

@@ -82,7 +82,7 @@ pub fn read_module<
 
         func_assoc: Map::new(),
         signatures: Map::new(),
-        backend: MCG::backend_id(),
+        backend: MCG::backend_id().to_string(),
 
         namespace_table: StringTable::new(),
         name_table: StringTable::new(),

lib/singlepass-backend/src/codegen_x64.rs

@@ -59,6 +59,8 @@ pub const INLINE_BREAKPOINT_SIZE_X86_SINGLEPASS: usize = 7;
 /// Inline breakpoint size for aarch64.
 pub const INLINE_BREAKPOINT_SIZE_AARCH64_SINGLEPASS: usize = 12;
 
+static BACKEND_ID: &str = "singlepass";
+
 #[cfg(target_arch = "x86_64")]
 lazy_static! {
     /// Performs a System V call to `target` with [stack_top..stack_base] as the argument list, from right to left.
@@ -651,8 +653,8 @@ impl ModuleCodeGenerator<X64FunctionCode, X64ExecutionContext, CodegenError>
         false
     }
 
-    fn backend_id() -> String {
-        "singlepass".to_string()
+    fn backend_id() -> &'static str {
+        BACKEND_ID
     }
 
     fn new_with_target(_: Option<String>, _: Option<String>, _: Option<String>) -> Self {