Merge #1143

1143: Set backend_id to static str r=MarkMcCaskey a=syrusakbary

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# Description

As per feedback in #1099, set backend_id to static str.

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Provide details regarding the change including motivation,
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# Review

- [ ] Add a short description of the the change to the CHANGELOG.md file


Co-authored-by: Syrus <me@syrusakbary.com>
Co-authored-by: Mark McCaskey <mark@wasmer.io>

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/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/runtime-core/src/state.rs

@@ -186,7 +186,7 @@ pub struct CodeVersion {
     pub base: usize,
 
     /// The backend used to compile this module.
-    pub backend: String,
+    pub backend: &'static str,
 
     /// `RunnableModule` for this code version.
     pub runnable_module: Arc<Box<dyn RunnableModule>>,

lib/runtime-core/src/tiering.rs

@@ -43,7 +43,7 @@ struct OptimizationState {
 }
 
 struct OptimizationOutcome {
-    backend_id: String,
+    backend_id: &'static str,
     module: Module,
 }
 
@@ -54,7 +54,7 @@ unsafe impl Sync for CtxWrapper {}
 
 unsafe fn do_optimize(
     binary: &[u8],
-    backend_id: String,
+    backend_id: &'static str,
     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: String,
-    optimized_backends: Vec<(String, Box<dyn Fn() -> Box<dyn Compiler> + Send>)>,
+    baseline_backend: &'static str,
+    optimized_backends: Vec<(&'static str, 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<(String, &mut Instance)> = {
+        let new_optimized: Option<(&'static str, &mut Instance)> = {
             let mut outcome = opt_state.outcome.lock().unwrap();
             if let Some(x) = outcome.take() {
                 let instance = x

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 {

src/bin/wasmer.rs

@@ -454,7 +454,7 @@ fn execute_wasi(
                 &import_object,
                 start_raw,
                 &mut instance,
-                options.backend,
+                options.backend.to_string(),
                 options
                     .optimized_backends
                     .iter()
@@ -462,7 +462,7 @@ fn execute_wasi(
                         |&backend| -> (Backend, Box<dyn Fn() -> Box<dyn Compiler> + Send>) {
                             let options = options.clone();
                             (
-                                backend,
+                                backend.to_string(),
                                 Box::new(move || {
                                     get_compiler_by_backend(backend, &options).unwrap()
                                 }),
@@ -492,7 +492,7 @@ fn execute_wasi(
                 baseline: true,
                 msm: msm,
                 base: instance.module.runnable_module.get_code().unwrap().as_ptr() as usize,
-                backend: options.backend.to_string().to_owned(),
+                backend: options.backend.to_string(),
                 runnable_module: instance.module.runnable_module.clone(),
             });
             true