New warning to report constant zero multiplications (#210)

MLanguage · Feb 8, 2023 · 0435165 · 0435165
2 parents 03e2fd2 + 480489c
commit 0435165
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diff --git a/src/mlang/backend_compilers/decoupledExpr.ml b/src/mlang/backend_compilers/decoupledExpr.ml
@@ -267,6 +267,7 @@ let mult (e1 : constr) (e2 : constr) (st : local_stacks) (ctx : local_vars) : t
   match (e1, e2) with
   | Dlit 1., _ -> (e2, Val, lv2)
   | _, Dlit 1. -> (e1, Val, lv1)
+  | Dlit 0., _ | _, Dlit 0. -> (Dlit 0., Val, [])
   | Dlit f1, Dlit f2 -> (Dlit (f1 *. f2), Val, [])
   | _ -> (Dbinop ("*", e1, e2), Val, lv2 @ lv1)
 

diff --git a/src/mlang/m_frontend/mast_to_mir.ml b/src/mlang/m_frontend/mast_to_mir.ml
@@ -969,6 +969,15 @@ let rec translate_expression (ctx : translating_context)
         let new_e2 = translate_expression ctx e2 in
         Mir.Comparison (op, new_e1, new_e2)
     | Mast.Binop (op, e1, e2) ->
+        if
+          Pos.unmark op = Mast.Mul
+          && (Pos.unmark e1 = Mast.Literal (Float 0.)
+             || Pos.unmark e2 = Mast.Literal (Float 0.))
+        then
+          (* It is difficult to do a broader or deeper analysis because of
+             constant substitutions that could wrongly trigger the warning *)
+          Errors.print_spanned_warning
+            "Nullifying constant multiplication found." (Pos.get_position f);
         let new_e1 = translate_expression ctx e1 in
         let new_e2 = translate_expression ctx e2 in
         Mir.Binop (op, new_e1, new_e2)