Add TORCH_TARGET_VERSION for stable ABI (pytorch#164356)

And update it so comparisons can be done by the preprocessor

**Note: We also need to gate in shim.h and figure out how to enforce this**

Differential Revision: [D85683549](https://our.internmc.facebook.com/intern/diff/D85683549)
Pull Request resolved: pytorch#164356
Approved by: https://github.com/janeyx99

Author: mikaylagawarecki

torch/csrc/stable/ops.h

@@ -245,4 +245,10 @@ inline torch::stable::Tensor clone(const torch::stable::Tensor& self) {
   return torch::stable::detail::to<torch::stable::Tensor>(stack[0]);
 }
 
+#if TORCH_FEATURE_VERSION >= TORCH_VERSION_2_10_0
+
+// New ops should be added here if they use a brand new shim API
+
+#endif
+
 HIDDEN_NAMESPACE_END(torch, stable)

torch/csrc/stable/version.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include <torch/headeronly/version.h>
+
+// Stable ABI Version Targeting
+//
+// This header provides version targeting capabilities for the PyTorch Stable
+// ABI. Users can define TORCH_TARGET_VERSION to target a specific stable ABI
+// version instead of using the current TORCH_ABI_VERSION of libtorch at
+// compile time.
+//
+// Usage:
+//   Default behavior (uses current ABI version):
+//     #include <torch/csrc/stable/library.h>
+//
+//   Target a specific stable version (major.minor) (e.g. PyTorch 2.9):
+//   (1) Pass a compiler flag -DTORCH_TARGET_VERSION=0x0209000000000000
+//   (2) Alternatively, define TORCH_TARGET_VERSION in the source code before
+//   including any header files:
+//     #define TORCH_TARGET_VERSION (((0ULL + 2) << 56) | ((0ULL + 9) << 48))
+//     #include <torch/csrc/stable/library.h>
+
+#ifdef TORCH_TARGET_VERSION
+#define TORCH_FEATURE_VERSION TORCH_TARGET_VERSION
+#else
+#define TORCH_FEATURE_VERSION TORCH_ABI_VERSION
+#endif
+
+#define TORCH_VERSION_2_10_0 (((0ULL + 2) << 56) | ((0ULL + 10) << 48))

torch/headeronly/version.h.in

@@ -19,8 +19,8 @@
 /// Indicates the ABI version of LibTorch as a single uint64.
 /// [ byte ][ byte ][ byte ][ byte ][ byte ][ byte ][ byte ][ byte ]
 /// [ MAJ  ][ MIN  ][ PATCH][                              ABI TAG ]
-#define TORCH_ABI_VERSION \
-  (uint64_t)TORCH_VERSION_MAJOR << 56 | \
-  (uint64_t)TORCH_VERSION_MINOR << 48 | \
-  (uint64_t)TORCH_VERSION_PATCH << 40 | \
-  TORCH_VERSION_ABI_TAG << 0
+#define TORCH_ABI_VERSION ( \
+  ((0ULL + TORCH_VERSION_MAJOR) << 56) | \
+  ((0ULL + TORCH_VERSION_MINOR) << 48) | \
+  ((0ULL + TORCH_VERSION_PATCH) << 40) | \
+  ((0ULL + TORCH_VERSION_ABI_TAG) << 0))