Remove global state for trap registration (#909)

* Remove global state for trap registration

There's a number of changes brought about in this commit, motivated by a
few things. One motivation was to remove an instance of using
`lazy_static!` in an effort to remove global state and encapsulate it
wherever possible. A second motivation came when investigating a
slowly-compiling wasm module (a bit too slowly) where a good chunk of
time was spent in managing trap registrations.

The specific change made here is that `TrapRegistry` is now stored
inside of a `Compiler` instead of inside a global. Additionally traps
are "bulk registered" for a module rather than one-by-one. This form of
bulk-registration allows optimizing the locks used here, where a lock is
only held for a module at-a-time instead of once-per-function.

With these changes the "unregister" logic has also been tweaked a bit
here and there to continue to work. As a nice side effect the `Compiler`
type now has one fewer field that requires actual mutability and has
been updated for multi-threaded compilation, nudging us closer to a
world where we can support multi-threaded compilation. Yay!

In terms of performance improvements, a local wasm test file that
previously took 3 seconds to compile is now 10% faster to compile,
taking ~2.7 seconds now.

* Perform trap resolution after unwinding

This avoids taking locks in signal handlers which feels a bit iffy...

* Remove `TrapRegistration::dummy()`

Avoid an case where you're trying to lookup trap information from a
dummy module for something that happened in a different module.

* Tweak some comments

crates/jit/src/instantiate.rs

@@ -18,7 +18,7 @@ use wasmtime_environ::{
     CompileError, DataInitializer, DataInitializerLocation, Module, ModuleEnvironment,
 };
 use wasmtime_runtime::{
-    GdbJitImageRegistration, InstanceHandle, InstantiationError, VMFunctionBody,
+    GdbJitImageRegistration, InstanceHandle, InstantiationError, TrapRegistration, VMFunctionBody,
     VMSharedSignatureIndex,
 };
 
@@ -52,6 +52,7 @@ struct RawCompiledModule<'data> {
     data_initializers: Box<[DataInitializer<'data>]>,
     signatures: BoxedSlice<SignatureIndex, VMSharedSignatureIndex>,
     dbg_jit_registration: Option<GdbJitImageRegistration>,
+    trap_registration: TrapRegistration,
 }
 
 impl<'data> RawCompiledModule<'data> {
@@ -73,12 +74,13 @@ impl<'data> RawCompiledModule<'data> {
             None
         };
 
-        let (allocated_functions, jt_offsets, relocations, dbg_image) = compiler.compile(
-            &translation.module,
-            translation.module_translation.as_ref().unwrap(),
-            translation.function_body_inputs,
-            debug_data,
-        )?;
+        let (allocated_functions, jt_offsets, relocations, dbg_image, trap_registration) = compiler
+            .compile(
+                &translation.module,
+                translation.module_translation.as_ref().unwrap(),
+                translation.function_body_inputs,
+                debug_data,
+            )?;
 
         link_module(
             &translation.module,
@@ -127,6 +129,7 @@ impl<'data> RawCompiledModule<'data> {
             data_initializers: translation.data_initializers.into_boxed_slice(),
             signatures: signatures.into_boxed_slice(),
             dbg_jit_registration,
+            trap_registration,
         })
     }
 }
@@ -138,6 +141,7 @@ pub struct CompiledModule {
     data_initializers: Box<[OwnedDataInitializer]>,
     signatures: BoxedSlice<SignatureIndex, VMSharedSignatureIndex>,
     dbg_jit_registration: Option<Rc<GdbJitImageRegistration>>,
+    trap_registration: TrapRegistration,
 }
 
 impl CompiledModule {
@@ -159,6 +163,7 @@ impl CompiledModule {
                 .into_boxed_slice(),
             raw.signatures.clone(),
             raw.dbg_jit_registration,
+            raw.trap_registration,
         ))
     }
 
@@ -169,6 +174,7 @@ impl CompiledModule {
         data_initializers: Box<[OwnedDataInitializer]>,
         signatures: BoxedSlice<SignatureIndex, VMSharedSignatureIndex>,
         dbg_jit_registration: Option<GdbJitImageRegistration>,
+        trap_registration: TrapRegistration,
     ) -> Self {
         Self {
             module: Arc::new(module),
@@ -176,6 +182,7 @@ impl CompiledModule {
             data_initializers,
             signatures,
             dbg_jit_registration: dbg_jit_registration.map(Rc::new),
+            trap_registration,
         }
     }
 
@@ -203,6 +210,7 @@ impl CompiledModule {
         let imports = resolve_imports(&self.module, resolver)?;
         InstanceHandle::new(
             Arc::clone(&self.module),
+            self.trap_registration.clone(),
             self.finished_functions.clone(),
             imports,
             &data_initializers,