WIP faster ord(str[i])

python · JukkaL · Jan 13, 2026 · Jan 13, 2026 · Jan 13, 2026 · Jan 13, 2026
commit 9e75d865475fbbe2c929a14f72a94f19a46dca10
diff --git a/mypyc/irbuild/specialize.py b/mypyc/irbuild/specialize.py
@@ -24,6 +24,7 @@
     DictExpr,
     Expression,
     GeneratorExpr,
+    IndexExpr,
     IntExpr,
     ListExpr,
     MemberExpr,
@@ -1129,6 +1130,21 @@ def translate_ord(builder: IRBuilder, expr: CallExpr, callee: RefExpr) -> Value
     arg = constant_fold_expr(builder, expr.args[0])
     if isinstance(arg, (str, bytes)) and len(arg) == 1:
         return Integer(ord(arg))
+
+    # Check for ord(s[i]) pattern where s is str and i is a native integer
+    arg_expr = expr.args[0]
+    if isinstance(arg_expr, IndexExpr):
+        # Check if base is a string
+        base_type = builder.node_type(arg_expr.base)
+        if base_type == str_rprimitive:
+            # Check if the index has one argument and it's a native integer type
+            index_expr = arg_expr.index
+            index_type = builder.node_type(index_expr)
+            if is_int_rprimitive(index_type) or is_fixed_width_rtype(index_type):
+                # This is ord(s[i]) where s is str and i is a native integer
+                # TODO: Generate specialized code here
+                assert False, "ord(s[i]) specialization not yet implemented"
+
     return None
 
 

diff --git a/mypyc/test-data/irbuild-str.test b/mypyc/test-data/irbuild-str.test
@@ -507,6 +507,15 @@ L0:
     r6 = unbox(int, r5)
     return r6
 
+[case testOrdOfStrIndex]
+from mypy_extensions import i64
+def ord_str_index(s: str, i: int) -> int:
+    return ord(s[i])
+def ord_str_index_i64(s: str, i: i64) -> int:
+    return ord(s[i])
+[typing fixtures/typing-full.pyi]
+[out]
+
 [case testStrip]
 from typing import NewType, Union
 NewStr = NewType("NewStr", str)