Update remaining locations to use a &'static str for backend

Cargo.lock

@@ -558,7 +558,7 @@ dependencies = [
  "libc",
  "llvm-sys",
  "once_cell",
- "parking_lot",
+ "parking_lot 0.10.0",
  "regex",
 ]
 
@@ -827,6 +827,17 @@ dependencies = [
  "md5",
 ]
 
+[[package]]
+name = "parking_lot"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f842b1982eb6c2fe34036a4fbfb06dd185a3f5c8edfaacdf7d1ea10b07de6252"
+dependencies = [
+ "lock_api",
+ "parking_lot_core 0.6.2",
+ "rustc_version",
+]
+
 [[package]]
 name = "parking_lot"
 version = "0.10.0"
@@ -834,7 +845,22 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "92e98c49ab0b7ce5b222f2cc9193fc4efe11c6d0bd4f648e374684a6857b1cfc"
 dependencies = [
  "lock_api",
- "parking_lot_core",
+ "parking_lot_core 0.7.0",
+]
+
+[[package]]
+name = "parking_lot_core"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b876b1b9e7ac6e1a74a6da34d25c42e17e8862aa409cbbbdcfc8d86c6f3bc62b"
+dependencies = [
+ "cfg-if",
+ "cloudabi",
+ "libc",
+ "redox_syscall",
+ "rustc_version",
+ "smallvec 0.6.13",
+ "winapi",
 ]
 
 [[package]]
@@ -1800,7 +1826,7 @@ dependencies = [
  "libc",
  "nix",
  "page_size",
- "parking_lot",
+ "parking_lot 0.9.0",
  "rustc_version",
  "serde",
  "serde-bench",

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

src/bin/wasmer.rs

@@ -448,7 +448,7 @@ fn execute_wasi(
                 &import_object,
                 start_raw,
                 &mut instance,
-                options.backend,
+                options.backend.to_string(),
                 options
                     .optimized_backends
                     .iter()
@@ -456,7 +456,7 @@ 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()
                                 }),