Add new_empty (with dtype argument only) to torch::stable (#159508)

Pull Request resolved: https://github.com/pytorch/pytorch/pull/159508
Approved by: https://github.com/janeyx99
ghstack dependencies: #160557

torchgen/aoti/fallback_ops.py

@@ -186,4 +186,5 @@ aten_shimified_ops: dict[str, dict[str, list[str]]] = {
     "aten.pad.default": {},
     "aten.narrow.default": {},
     "aten.amax.default": {},
+    "aten.new_empty.default": {},
 }

torchgen/gen_aoti_c_shim.py

@@ -24,6 +24,7 @@ from torchgen.model import (
     OperatorName,
     OptionalType,
     Type,
+    Variant,
 )
 from torchgen.utils import FileManager, mapMaybe
 
@@ -396,7 +397,22 @@ def gen_static_dispatch_backend_call(
 ) -> str:
     sig = DispatcherSignature.from_schema(f.func)
     cpp_sig = gen_static_dispatch_backend_call_signature(sig, f)
+
     if backend_index is None:
+        # Check if this is a symint function and if the function only has method variants
+        if sig.symint and f.func.has_symint():
+            has_function_variant = Variant.function in f.variants
+
+            if not has_function_variant:
+                # Functions with both function and method variants can use the at::{*}_symint version
+                # (e.g., narrow -> at::narrow_symint), BUT
+                # Method-only functions with symint parameters should use at::symint:: namespace
+                # Remove the _symint suffix since at::symint:: namespace uses the base name
+                # (e.g., new_empty -> at::symint::new_empty<c10::SymInt>)
+                base_name = cpp_sig.name()
+                base_name = base_name.removesuffix("_symint")  # Remove "_symint" suffix
+                return f"at::symint::{base_name}<c10::SymInt>"
+
         return f"at::{cpp_sig.name()}"
     else:
         return f"at::{backend_index.dispatch_key.lower()}::{cpp_sig.name()}"