--- a/js/src/wasm/cranelift/src/wasm2clif.rs
+++ b/js/src/wasm/cranelift/src/wasm2clif.rs
@@ -110,17 +110,21 @@ pub fn init_sig(
     init_sig_from_wsig(call_conv, wsig)
 }
 
 /// An instance call may return a special value to indicate that the operation
 /// failed and we need to trap. This indicates what kind of value to check for,
 /// if any.
 enum FailureMode {
     Infallible,
-    NotZero,
+    /// The value returned by the function must be checked. internal_ret set to true indicates that
+    /// the returned value is only used internally, and should not be passed back to wasm.
+    NotZero {
+        internal_ret: bool,
+    },
 }
 
 /// A description of builtin call to the `wasm::Instance`.
 struct InstanceCall {
     address: SymbolicAddress,
     arguments: &'static [ir::Type],
     ret: Option<ir::Type>,
     failure_mode: FailureMode,
@@ -139,52 +143,52 @@ const FN_MEMORY_SIZE: InstanceCall = Ins
     arguments: &[],
     ret: Some(ir::types::I32),
     failure_mode: FailureMode::Infallible,
 };
 const FN_MEMORY_COPY: InstanceCall = InstanceCall {
     address: SymbolicAddress::MemoryCopy,
     arguments: &[ir::types::I32, ir::types::I32, ir::types::I32, POINTER_TYPE],
     ret: Some(ir::types::I32),
-    failure_mode: FailureMode::NotZero,
+    failure_mode: FailureMode::NotZero { internal_ret: true },
 };
 const FN_MEMORY_COPY_SHARED: InstanceCall = InstanceCall {
     address: SymbolicAddress::MemoryCopyShared,
     arguments: &[ir::types::I32, ir::types::I32, ir::types::I32, POINTER_TYPE],
     ret: Some(ir::types::I32),
-    failure_mode: FailureMode::NotZero,
+    failure_mode: FailureMode::NotZero { internal_ret: true },
 };
 const FN_MEMORY_FILL: InstanceCall = InstanceCall {
     address: SymbolicAddress::MemoryFill,
     arguments: &[ir::types::I32, ir::types::I32, ir::types::I32, POINTER_TYPE],
     ret: Some(ir::types::I32),
-    failure_mode: FailureMode::NotZero,
+    failure_mode: FailureMode::NotZero { internal_ret: true },
 };
 const FN_MEMORY_FILL_SHARED: InstanceCall = InstanceCall {
     address: SymbolicAddress::MemoryFillShared,
     arguments: &[ir::types::I32, ir::types::I32, ir::types::I32, POINTER_TYPE],
     ret: Some(ir::types::I32),
-    failure_mode: FailureMode::NotZero,
+    failure_mode: FailureMode::NotZero { internal_ret: true },
 };
 const FN_MEMORY_INIT: InstanceCall = InstanceCall {
     address: SymbolicAddress::MemoryInit,
     arguments: &[
         ir::types::I32,
         ir::types::I32,
         ir::types::I32,
         ir::types::I32,
     ],
     ret: Some(ir::types::I32),
-    failure_mode: FailureMode::NotZero,
+    failure_mode: FailureMode::NotZero { internal_ret: true },
 };
 const FN_DATA_DROP: InstanceCall = InstanceCall {
     address: SymbolicAddress::DataDrop,
     arguments: &[ir::types::I32],
     ret: Some(ir::types::I32),
-    failure_mode: FailureMode::NotZero,
+    failure_mode: FailureMode::NotZero { internal_ret: true },
 };
 const FN_TABLE_SIZE: InstanceCall = InstanceCall {
     address: SymbolicAddress::TableSize,
     arguments: &[ir::types::I32],
     ret: Some(ir::types::I32),
     failure_mode: FailureMode::Infallible,
 };
 const FN_TABLE_COPY: InstanceCall = InstanceCall {
@@ -192,35 +196,35 @@ const FN_TABLE_COPY: InstanceCall = Inst
     arguments: &[
         ir::types::I32,
         ir::types::I32,
         ir::types::I32,
         ir::types::I32,
         ir::types::I32,
     ],
     ret: Some(ir::types::I32),
-    failure_mode: FailureMode::NotZero,
+    failure_mode: FailureMode::NotZero { internal_ret: true },
 };
 const FN_TABLE_INIT: InstanceCall = InstanceCall {
     address: SymbolicAddress::TableInit,
     arguments: &[
         ir::types::I32,
         ir::types::I32,
         ir::types::I32,
         ir::types::I32,
         ir::types::I32,
     ],
     ret: Some(ir::types::I32),
-    failure_mode: FailureMode::NotZero,
+    failure_mode: FailureMode::NotZero { internal_ret: true },
 };
 const FN_ELEM_DROP: InstanceCall = InstanceCall {
     address: SymbolicAddress::ElemDrop,
     arguments: &[ir::types::I32],
     ret: Some(ir::types::I32),
-    failure_mode: FailureMode::NotZero,
+    failure_mode: FailureMode::NotZero { internal_ret: true },
 };
 
 // Custom trap codes specific to this embedding
 
 pub const TRAP_THROW_REPORTED: u16 = 1;
 
 /// A `TargetIsa` and `ModuleEnvironment` joined so we can implement `FuncEnvironment`.
 pub struct TransEnv<'a, 'b, 'c> {
@@ -553,23 +557,27 @@ impl<'a, 'b, 'c> TransEnv<'a, 'b, 'c> {
         self.reload_tls_and_pinned_regs(pos);
 
         if call.ret.is_none() {
             return None;
         }
 
         let ret = pos.func.dfg.first_result(call_ins);
         match call.failure_mode {
-            FailureMode::Infallible => {}
-            FailureMode::NotZero => {
+            FailureMode::Infallible => Some(ret),
+            FailureMode::NotZero { internal_ret } => {
                 pos.ins()
                     .trapnz(ret, ir::TrapCode::User(TRAP_THROW_REPORTED));
+                if internal_ret {
+                    None
+                } else {
+                    Some(ret)
+                }
             }
         }
-        Some(ret)
     }
 }
 
 impl<'a, 'b, 'c> TargetEnvironment for TransEnv<'a, 'b, 'c> {
     fn target_config(&self) -> TargetFrontendConfig {
         self.isa.frontend_config()
     }
 
@@ -1028,21 +1036,17 @@ impl<'a, 'b, 'c> FuncEnvironment for Tra
         len: ir::Value,
     ) -> WasmResult<()> {
         assert!(dst_table_index.index() == 0);
         assert!(src_table_index.index() == 0);
         // Slightly lower the amount of SSA nodes as `dst == src`
         let index = pos
             .ins()
             .iconst(ir::types::I32, dst_table_index.index() as i64);
-        let ret = self.instance_call(
-            &mut pos,
-            &FN_TABLE_COPY,
-            &[dst, src, len, index, index],
-        );
+        let ret = self.instance_call(&mut pos, &FN_TABLE_COPY, &[dst, src, len, index, index]);
         debug_assert!(ret.is_none());
         Ok(())
     }
 
     fn translate_table_init(
         &mut self,
         mut pos: FuncCursor,
         seg_index: u32,