Remove the NullI31Ref trap code

To precisely match the Wasm spec tests, we would also need `NullStructRef` and
`NullArrayRef`, etc... This is not practical, given the encoding space we have
available. We are already matching expected "null FOO reference" trap messages
when running the spec tests to our own "null reference" messages, so we can do
that for `i31`s as well.

cranelift/codegen/src/ir/memflags.rs

@@ -361,7 +361,7 @@ impl MemFlags {
             0b1001 => Some(TrapCode::UnreachableCodeReached),
             0b1010 => Some(TrapCode::Interrupt),
             0b1011 => Some(TrapCode::NullReference),
-            0b1100 => Some(TrapCode::NullI31Ref),
+            // 0b1100 => {} not allocated
             // 0b1101 => {} not allocated
             // 0b1110 => {} not allocated
             0b1111 => None,
@@ -390,7 +390,6 @@ impl MemFlags {
             Some(TrapCode::UnreachableCodeReached) => 0b1001,
             Some(TrapCode::Interrupt) => 0b1010,
             Some(TrapCode::NullReference) => 0b1011,
-            Some(TrapCode::NullI31Ref) => 0b1100,
             None => 0b1111,
 
             Some(TrapCode::User(_)) => panic!("cannot set user trap code in mem flags"),

cranelift/codegen/src/ir/trapcode.rs

@@ -53,9 +53,6 @@ pub enum TrapCode {
 
     /// A null reference was encountered which was required to be non-null.
     NullReference,
-
-    /// A null `i31ref` was encountered which was required to be non-null.
-    NullI31Ref,
 }
 
 impl TrapCode {
@@ -95,7 +92,6 @@ impl Display for TrapCode {
             Interrupt => "interrupt",
             User(x) => return write!(f, "user{x}"),
             NullReference => "null_reference",
-            NullI31Ref => "null_i31ref",
         };
         f.write_str(identifier)
     }
@@ -119,7 +115,6 @@ impl FromStr for TrapCode {
             "unreachable" => Ok(UnreachableCodeReached),
             "interrupt" => Ok(Interrupt),
             "null_reference" => Ok(NullReference),
-            "null_i31ref" => Ok(NullI31Ref),
             _ if s.starts_with("user") => s[4..].parse().map(User).map_err(|_| ()),
             _ => Err(()),
         }

crates/cranelift-shared/src/lib.rs

@@ -86,7 +86,6 @@ pub fn mach_trap_to_trap(trap: &MachTrap) -> Option<TrapInformation> {
             ir::TrapCode::User(ALWAYS_TRAP_CODE) => Trap::AlwaysTrapAdapter,
             ir::TrapCode::User(CANNOT_ENTER_CODE) => Trap::CannotEnterComponent,
             ir::TrapCode::NullReference => Trap::NullReference,
-            ir::TrapCode::NullI31Ref => Trap::NullI31Ref,
 
             // These do not get converted to wasmtime traps, since they
             // shouldn't ever be hit in theory. Instead of catching and handling

crates/cranelift/src/func_environ.rs

@@ -1851,7 +1851,7 @@ impl<'module_environment> cranelift_wasm::FuncEnvironment for FuncEnvironment<'m
         // TODO: If we knew we have a `(ref i31)` here, instead of maybe a `(ref
         // null i31)`, we could omit the `trapz`. But plumbing that type info
         // from `wasmparser` and through to here is a bit funky.
-        self.trapz(builder, i31ref, ir::TrapCode::NullI31Ref);
+        self.trapz(builder, i31ref, ir::TrapCode::NullReference);
         Ok(builder.ins().sshr_imm(i31ref, 1))
     }
 
@@ -1863,7 +1863,7 @@ impl<'module_environment> cranelift_wasm::FuncEnvironment for FuncEnvironment<'m
         // TODO: If we knew we have a `(ref i31)` here, instead of maybe a `(ref
         // null i31)`, we could omit the `trapz`. But plumbing that type info
         // from `wasmparser` and through to here is a bit funky.
-        self.trapz(builder, i31ref, ir::TrapCode::NullI31Ref);
+        self.trapz(builder, i31ref, ir::TrapCode::NullReference);
         Ok(builder.ins().ushr_imm(i31ref, 1))
     }
 

crates/cranelift/src/lib.rs

@@ -248,7 +248,6 @@ fn clif_trap_to_env_trap(trap: ir::TrapCode) -> Option<Trap> {
         ir::TrapCode::User(ALWAYS_TRAP_CODE) => Trap::AlwaysTrapAdapter,
         ir::TrapCode::User(CANNOT_ENTER_CODE) => Trap::CannotEnterComponent,
         ir::TrapCode::NullReference => Trap::NullReference,
-        ir::TrapCode::NullI31Ref => Trap::NullI31Ref,
 
         // These do not get converted to wasmtime traps, since they
         // shouldn't ever be hit in theory. Instead of catching and handling

crates/environ/src/trap_encoding.rs

@@ -74,9 +74,6 @@ pub enum Trap {
     /// Call to a null reference.
     NullReference,
 
-    /// Attempt to get the bits of a null `i31ref`.
-    NullI31Ref,
-
     /// When the `component-model` feature is enabled this trap represents a
     /// scenario where one component tried to call another component but it
     /// would have violated the reentrance rules of the component model,
@@ -114,7 +111,6 @@ impl Trap {
             OutOfFuel
             AtomicWaitNonSharedMemory
             NullReference
-            NullI31Ref
             CannotEnterComponent
         }
 
@@ -142,7 +138,6 @@ impl fmt::Display for Trap {
             OutOfFuel => "all fuel consumed by WebAssembly",
             AtomicWaitNonSharedMemory => "atomic wait on non-shared memory",
             NullReference => "null reference",
-            NullI31Ref => "null i31 reference",
             CannotEnterComponent => "cannot enter component instance",
         };
         write!(f, "wasm trap: {desc}")