[WIP] Typ aided removal of redundant modulus.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index 996eecd361caacde8ae062304ac1180d68902e75..ce1ea188336830c0b15579ea8c4f62ac33e45d9d 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -467,6 +467,10 @@ Type* Typer::Visitor::NumberToInt32(Type* type, Typer* t) {
   // TODO(neis): DCHECK(type->Is(Type::Number()));
   if (type->Is(Type::Signed32())) return type;
   if (type->Is(t->zeroish)) return t->singleton_zero;
+  if (type->Is(Type::Union(Type::MinusZero(), Type::Signed32(), t->zone()))) {
+    return Type::Intersect(Type::Union(type, t->singleton_zero, t->zone()),
+                           Type::Signed32(), t->zone());
+  }
   return Type::Signed32();
 }