ZJIT: Adjust Type API for checking signedness

Author: tekknolagi

zjit/src/hir.rs

@@ -5296,7 +5296,7 @@ impl Function {
                     }
                     Insn::AdjustBounds { index, .. } => {
                         // If index is known nonnegative, then we don't need to adjust bounds.
-                        if self.type_of(index).cint64_value().filter(|&i| i >= 0).is_some() {
+                        if self.type_of(index).known_nonnegative() {
                             self.make_equal_to(insn_id, index);
                             // Don't bother re-inferring the type of index; we already know it.
                             continue;

zjit/src/hir_type/mod.rs

@@ -411,6 +411,19 @@ impl Type {
         }
     }
 
+    fn int_spec_signed(&self) -> Option<i64> {
+        assert!(self.is_subtype(types::CSigned), "int_spec_signed() only makes sense for signed integer types");
+        match self.spec {
+            Specialization::Int(val) => Some(val as i64),
+            _ => None,
+        }
+    }
+
+    pub fn known_nonnegative(&self) -> bool {
+        assert!(self.is_subtype(types::CSigned), "nonnegative() only makes sense for signed integer types");
+        self.int_spec_signed().map_or(false, |val| val >= 0)
+    }
+
     /// Return true if the Type has object specialization and false otherwise.
     pub fn ruby_object_known(&self) -> bool {
         matches!(self.spec, Specialization::Object(_))