Fix overflow operations

Author: antoyo

Diff for: src/int.rs

@@ -404,7 +404,7 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
 
         let ret_indirect = matches!(fn_abi.ret.mode, PassMode::Indirect { .. });
 
-        let result = if ret_indirect {
+        let call = if ret_indirect {
             let res_value = self.current_func().new_local(self.location, res_type, "result_value");
             let res_addr = res_value.get_address(self.location);
             let res_param_type = res_type.make_pointer();
@@ -432,8 +432,17 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
             );
             self.context.new_call(self.location, func, &[lhs, rhs, overflow_addr])
         };
-
-        (result, self.context.new_cast(self.location, overflow_value, self.bool_type).to_rvalue())
+        // NOTE: we must assign the result of the operation to a variable at this point to make
+        // sure it will be evaluated by libgccjit now.
+        // Otherwise, it will only be evaluated when the rvalue for the call is used somewhere else
+        // and overflow_value will not be initialized at the correct point in the program.
+        let result = self.current_func().new_local(self.location, res_type, "result");
+        self.block.add_assignment(self.location, result, call);
+
+        (
+            result.to_rvalue(),
+            self.context.new_cast(self.location, overflow_value, self.bool_type).to_rvalue(),
+        )
     }
 
     pub fn gcc_icmp(
@@ -865,6 +874,7 @@ impl<'gcc, 'tcx> CodegenCx<'gcc, 'tcx> {
         let value_type = value.get_type();
         if self.is_native_int_type_or_bool(dest_typ) && self.is_native_int_type_or_bool(value_type)
         {
+            // TODO: use self.location.
             self.context.new_cast(None, value, dest_typ)
         } else if self.is_native_int_type_or_bool(dest_typ) {
             self.context.new_cast(None, self.low(value), dest_typ)