Add tests

Lib/test/test_capi/test_opt.py

@@ -1515,9 +1515,33 @@ def test_jit_error_pops(self):
         with self.assertRaises(TypeError):
             {item for item in items}
 
+    def test_global_guard_hoisted_if_possible(self):
+        def testfunc(n):
+            for i in range(n):
+                # Only works on functions promoted to constants
+                # The inner global promoted guard should be hoisted out.
+                global_foo(i)
+
+        opt = _testinternalcapi.new_uop_optimizer()
+        with temporary_optimizer(opt):
+            testfunc(20)
+
+        ex = get_first_executor(testfunc)
+        self.assertIsNotNone(ex)
+        uops = get_opnames(ex)
+        opnames = list(iter_opnames(ex))
+        self.assertIn("_PUSH_FRAME", uops)
+        # Hoisted version
+        self.assertIn("_CHECK_FUNCTION_STACK", uops)
+        # Only 1 outer guard
+        self.assertLessEqual(opnames.count("_CHECK_FUNCTION"), 1)
 
 def global_identity(x):
     return x
 
+def global_foo(x):
+    return global_identity(x)
+
+
 if __name__ == "__main__":
     unittest.main()

Python/optimizer_bytecodes.c

@@ -594,7 +594,21 @@ dummy_func(void) {
         // with partial evaluation later on.
         (void)func_version;
         if (ctx->frame->frame_creation_inst != NULL) {
+            // Already hoisted. Slot can't be used again.
+            if ((ctx->frame->frame_creation_inst - 1)->opcode == _CHECK_FUNCTION_STACK) {
+                break;
+            }
             assert((ctx->frame->frame_creation_inst - 1)->opcode == _NOP);
+            bool has_interfering_inst = false;
+            for (_PyUOpInstruction *start = ctx->frame->frame_creation_inst + 1; start < this_instr; start++) {
+                if (_PyUop_Flags[start->opcode] & HAS_ESCAPES_FLAG) {
+                    has_interfering_inst = true;
+                    break;
+                }
+            }
+            if (has_interfering_inst) {
+                break;
+            }
             *(ctx->frame->frame_creation_inst - 1) = *this_instr;
             (ctx->frame->frame_creation_inst - 1)->opcode = _CHECK_FUNCTION_STACK;
             (ctx->frame->frame_creation_inst - 1)->oparg = ctx->frame->frame_creation_inst->oparg;