GH-130415: Optimize constant comparison in JIT builds

Lib/test/test_capi/test_opt.py

@@ -1564,6 +1564,23 @@ def f(n):
         # But all of the appends we care about are still there:
         self.assertEqual(uops.count("_CALL_LIST_APPEND"), len("ABCDEFG"))
 
+def test_compare_pop_two_load_const_inline_borrow(self):
+        def testfunc(n):
+            x = 0
+            for _ in range(n):
+                a = 10
+                b = 10
+                if a == b:
+                    x += 1
+            return x
+
+        res, ex = self._run_with_optimizer(testfunc, TIER2_THRESHOLD)
+        self.assertEqual(res, 1)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        self.assertNotIn("_COMPARE_OP_INT", uops)
+        self.assertIn("_POP_TWO_LOAD_CONST_INLINE_BORROW", uops)
+
 def global_identity(x):
     return x
 

Misc/NEWS.d/next/Core_and_Builtins/2025-03-20-03-45-20.gh-issue-130415.VtJhoG.rst

@@ -0,0 +1 @@
+Optimize comparison of two constants in JIT builds

Python/bytecodes.c

@@ -5132,6 +5132,12 @@ dummy_func(
             value = PyStackRef_FromPyObjectImmortal(ptr);
         }
 
+        tier2 pure op (_POP_TWO_LOAD_CONST_INLINE_BORROW, (ptr/4, pop1, pop2 -- value)) {
+            PyStackRef_CLOSE(pop2);
+            PyStackRef_CLOSE(pop1);
+            value = PyStackRef_FromPyObjectImmortal(ptr);
+        }
+
         tier2 op(_CHECK_FUNCTION, (func_version/2 -- )) {
             assert(PyStackRef_FunctionCheck(frame->f_funcobj));
             PyFunctionObject *func = (PyFunctionObject *)PyStackRef_AsPyObjectBorrow(frame->f_funcobj);

Python/optimizer_bytecodes.c

@@ -446,7 +446,30 @@ dummy_func(void) {
     }
 
     op(_COMPARE_OP_INT, (left, right -- res)) {
-        res = sym_new_type(ctx, &PyBool_Type);
+        if (sym_is_const(ctx, left) && sym_is_const(ctx, right) &&
+        sym_matches_type(left, &PyLong_Type) && sym_matches_type(right, &PyLong_Type))
+        {
+            assert(PyLong_CheckExact(sym_get_const(ctx, left)));
+            assert(PyLong_CheckExact(sym_get_const(ctx, right)));
+            PyObject *tmp = PyObject_RichCompare(sym_get_const(ctx, left),
+                                                 sym_get_const(ctx, right),
+                                                 oparg >> 5);
+            if (tmp == NULL) {
+                goto error;
+            }
+            res = sym_new_const(ctx, tmp);
+            Py_DECREF(tmp);
+
+            if (_Py_IsImmortal(res)) {
+                REPLACE_OP(this_instr, _POP_TWO_LOAD_CONST_INLINE_BORROW, 0, (uintptr_t)tmp);
+            }
+            else {
+                res = sym_new_type(ctx, &PyBool_Type);
+            }
+        }
+        else {
+            res = sym_new_type(ctx, &PyBool_Type);
+        }
     }
 
     op(_COMPARE_OP_FLOAT, (left, right -- res)) {