winch: Fix the type of the table.size output register (#13009)

This commit corrects the tagged size of the output of the `table.size`
instruction. Previously this was hardcoded as a 32-bit integer instead
of consulting the table's index type to use the
index-type-sized-register instead.

Author: alexcrichton

tests/misc_testsuite/winch/table64.wast

@@ -0,0 +1,15 @@
+;;! memory64 = true
+;;! reference_types = true
+
+(module
+  (table $t i64 10 funcref)
+  (func $leak (result i64 i64)
+    table.size $t
+    table.size $t
+  )
+  (func (export "test") (result i64)
+    call $leak
+    drop
+  )
+)
+(assert_return (invoke "test") (i64.const 10))

winch/codegen/src/codegen/env.rs

@@ -41,6 +41,17 @@ pub struct TableData {
     pub(crate) element_size: OperandSize,
     /// The size of the current elements field.
     pub(crate) current_elements_size: OperandSize,
+    /// The type of this table.
+    pub ty: Table,
+}
+
+impl TableData {
+    pub fn index_type(&self) -> WasmValType {
+        match self.ty.idx_type {
+            IndexType::I32 => WasmValType::I32,
+            IndexType::I64 => WasmValType::I64,
+        }
+    }
 }
 
 /// Heap metadata.
@@ -246,6 +257,7 @@ impl<'a, 'translation, 'data, P: PtrSize> FuncEnv<'a, 'translation, 'data, P> {
                     current_elements_size: OperandSize::from_bytes(
                         self.vmoffsets.size_of_vmtable_definition_current_elements(),
                     ),
+                    ty: self.translation.module.tables[index],
                 })
             }
         }

winch/codegen/src/codegen/mod.rs

@@ -1073,7 +1073,8 @@ where
             masm.load(size_addr, writable!(size), table_data.current_elements_size)
         })?;
 
-        self.context.stack.push(TypedReg::i32(size).into());
+        let dst = TypedReg::new(table_data.index_type(), size);
+        self.context.stack.push(dst.into());
         Ok(())
     }