Move trap information to a section of the compiled image (#3241)

This commit moves the `traps` field of `FunctionInfo` into a section of
the compiled artifact produced by Cranelift. This section is quite large
and when previously encoded/decoded with `bincode` this can take quite
some time to process. Traps are expected to be relatively rare and it's
not necessarily the right tradeoff to spend so much time
serializing/deserializing this data, so this commit offloads the section
into a custom-encoded binary format located elsewhere in the compiled image.

This is similar to #3240 in its goal which is to move very large pieces
of metadata to their own sections to avoid decoding anything when we
load a precompiled modules. This also has a small benefit that it's
slightly more efficient storage for the trap information too, but that's
a negligible benefit.

This is part of #3230 to make loading modules fast.

crates/wasmtime/src/module/registry.rs

@@ -5,7 +5,7 @@ use std::{
     collections::BTreeMap,
     sync::{Arc, RwLock},
 };
-use wasmtime_environ::{EntityRef, FilePos, StackMap, TrapInformation};
+use wasmtime_environ::{EntityRef, FilePos, StackMap, TrapCode};
 use wasmtime_jit::CompiledModule;
 use wasmtime_runtime::{ModuleInfo, VMCallerCheckedAnyfunc, VMTrampoline};
 
@@ -262,9 +262,9 @@ impl GlobalModuleRegistry {
     }
 
     /// Fetches trap information about a program counter in a backtrace.
-    pub(crate) fn lookup_trap_info(&self, pc: usize) -> Option<&TrapInformation> {
+    pub(crate) fn lookup_trap_code(&self, pc: usize) -> Option<TrapCode> {
         let (module, offset) = self.module(pc)?;
-        module.lookup_trap_info(offset)
+        wasmtime_environ::lookup_trap_code(module.module.trap_data(), offset)
     }
 
     /// Registers a new region of code, described by `(start, end)` and with
@@ -371,17 +371,6 @@ impl GlobalRegisteredModule {
             symbols,
         })
     }
-
-    /// Fetches trap information about a program counter in a backtrace.
-    pub fn lookup_trap_info(&self, text_offset: usize) -> Option<&TrapInformation> {
-        let (index, func_offset) = self.module.func_by_text_offset(text_offset)?;
-        let info = self.module.func_info(index);
-        let idx = info
-            .traps
-            .binary_search_by_key(&func_offset, |info| info.code_offset)
-            .ok()?;
-        Some(&info.traps[idx])
-    }
 }
 
 /// Description of a frame in a backtrace for a [`Trap`].

crates/wasmtime/src/trap.rs

@@ -172,8 +172,7 @@ impl Trap {
             } => {
                 let mut code = GlobalModuleRegistry::with(|modules| {
                     modules
-                        .lookup_trap_info(pc)
-                        .map(|info| info.trap_code)
+                        .lookup_trap_code(pc)
                         .unwrap_or(EnvTrapCode::StackOverflow)
                 });
                 if maybe_interrupted && code == EnvTrapCode::StackOverflow {