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Author: cfallin

crates/cranelift/src/func_environ.rs

@@ -2540,7 +2540,7 @@ impl FuncEnvironment<'_> {
         builder: &mut FunctionBuilder<'_>,
         tag_index: TagIndex,
         exn_ref: ir::Value,
-    ) -> WasmResult<Vec<ir::Value>> {
+    ) -> WasmResult<SmallVec<[ir::Value; 4]>> {
         gc::translate_exn_unbox(self, builder, tag_index, exn_ref)
     }
 

crates/cranelift/src/func_environ/gc/enabled.rs

@@ -10,7 +10,7 @@ use cranelift_codegen::{
 };
 use cranelift_entity::packed_option::ReservedValue;
 use cranelift_frontend::FunctionBuilder;
-use smallvec::SmallVec;
+use smallvec::{SmallVec, smallvec};
 use wasmtime_environ::{
     Collector, GcArrayLayout, GcLayout, GcStructLayout, I31_DISCRIMINANT, ModuleInternedTypeIndex,
     PtrSize, TagIndex, TypeIndex, VMGcKind, WasmCompositeInnerType, WasmHeapTopType, WasmHeapType,
@@ -414,7 +414,7 @@ pub fn translate_exn_unbox(
     builder: &mut FunctionBuilder<'_>,
     tag_index: TagIndex,
     exn_ref: ir::Value,
-) -> WasmResult<Vec<ir::Value>> {
+) -> WasmResult<SmallVec<[ir::Value; 4]>> {
     log::trace!("translate_exn_unbox({tag_index:?} {exn_ref:?})");
 
     // We know that the `exn_ref` is not null because we reach this
@@ -433,12 +433,12 @@ pub fn translate_exn_unbox(
     // Gather accesses first because these require a borrow on
     // `func_env`, which we later mutate below via
     // `prepare_gc_ref_access()`.
-    let mut accesses = vec![];
+    let mut accesses: SmallVec<[_; 4]> = smallvec![];
     for (field_ty, field_layout) in exception_ty.fields.iter().zip(exn_layout.fields.iter()) {
         accesses.push((field_layout.offset, field_ty.element_type));
     }
 
-    let mut result = vec![];
+    let mut result = smallvec![];
     for (field_offset, field_ty) in accesses {
         let field_size = wasmtime_environ::byte_size_of_wasm_ty_in_gc_heap(&field_ty);
         assert!(field_offset + field_size <= exn_size);

crates/wasmtime/src/runtime/code_memory.rs

@@ -188,7 +188,12 @@ impl CodeMemory {
 
         // Ensure that the exception table is well-formed. This parser
         // construction is cheap: it reads the header and validates
-        // ranges but nothing else.
+        // ranges but nothing else. We do this only in debug-assertion
+        // builds because we otherwise require for safety that the
+        // compiled artifact is as-produced-by this version of
+        // Wasmtime, and we should always produce a correct exception
+        // table (i.e., we are not expecting untrusted data here).
+        #[cfg(debug_assertions)]
         let _ = ExceptionTable::parse(&mmap[exception_data.clone()])?;
 
         Ok(Self {

crates/wasmtime/src/runtime/vm/gc/disabled.rs

@@ -26,14 +26,14 @@ impl VMGcRef {
 }
 
 impl From<VMStructRef> for VMGcRef {
-    fn from(_s: VMStructRef) -> VMGcRef {
-        unreachable!()
+    fn from(s: VMStructRef) -> VMGcRef {
+        match s {}
     }
 }
 
 impl From<VMExnRef> for VMGcRef {
-    fn from(_e: VMExnRef) -> VMGcRef {
-        unreachable!()
+    fn from(e: VMExnRef) -> VMGcRef {
+        match e {}
     }
 }
 

crates/wasmtime/src/runtime/vm/vmcontext.rs

@@ -355,6 +355,14 @@ mod test_vmtag_import {
             offset_of!(VMTagImport, from),
             usize::from(offsets.vmtag_import_from())
         );
+        assert_eq!(
+            offset_of!(VMTagImport, vmctx),
+            usize::from(offsets.vmtag_import_vmctx())
+        );
+        assert_eq!(
+            offset_of!(VMTagImport, index),
+            usize::from(offsets.vmtag_import_index())
+        );
     }
 }