From 66b73edb286fb5c0f1ace2b0b4b147bf9edbc3e7 Mon Sep 17 00:00:00 2001
From: Stella Laurenzo <stellaraccident@gmail.com>
Date: Wed, 22 Nov 2023 17:52:07 -0800
Subject: [PATCH] Move TORCH_MLIR_USE_INSTALLED_PYTORCH to top-level.

This was unfortunately being initialized in a directory below its first use. This was causing the first configure to mis-detect the ABI flags, which was causing type conversion failures at runtime.

Fixes #2298 and hardens some additional messages and checks to better make it clear when something goes awry.
---
 CMakeLists.txt                     |  2 ++
 projects/CMakeLists.txt            | 11 ++++++++++-
 projects/pt1/python/CMakeLists.txt |  2 --
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1114643a593b..ccbe7ccb3a98 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -29,6 +29,8 @@ set(CMAKE_CXX_STANDARD 17)
 # Project options
 #-------------------------------------------------------------------------------
 
+option(TORCH_MLIR_USE_INSTALLED_PYTORCH "If depending on PyTorch use it as installed in the current Python environment" ON)
+
 option(TORCH_MLIR_ENABLE_REFBACKEND "Enable reference backend" ON)
 if(TORCH_MLIR_ENABLE_REFBACKEND)
   add_definitions(-DTORCH_MLIR_ENABLE_REFBACKEND)
diff --git a/projects/CMakeLists.txt b/projects/CMakeLists.txt
index 2838570a8797..4b54be65a79d 100644
--- a/projects/CMakeLists.txt
+++ b/projects/CMakeLists.txt
@@ -12,6 +12,9 @@ if(TORCH_MLIR_ENABLE_JIT_IR_IMPORTER OR TORCH_MLIR_ENABLE_LTC)
     # Assume it is a sibling to the overall project.
     set(Torch_DIR "${PROJECT_SOURCE_DIR}/../libtorch/share/cmake/Torch")
     message(STATUS "Attempting to locate libtorch as a sibling to the project: ${Torch_DIR}")
+    if(NOT EXISTS "${Torch_DIR}")
+      message(FATAL_ERROR "Without TORCH_MLIR_USE_INSTALLED_PYTORCH, expected to find Torch configuration at ${Torch_DIR}, which does not exist")
+    endif()
   endif()
   
   find_package(Torch 1.11 REQUIRED)
@@ -23,7 +26,13 @@ if(TORCH_MLIR_ENABLE_JIT_IR_IMPORTER OR TORCH_MLIR_ENABLE_LTC)
     ${Python3_INCLUDE_DIRS}
   )
   link_directories("${TORCH_INSTALL_PREFIX}/lib")  
-  message(STATUS "libtorch_python CXXFLAGS is ...${TORCH_CXXFLAGS}")
+  message(STATUS "TORCH_CXXFLAGS is = ${TORCH_CXXFLAGS}")
+  if(${CMAKE_SYSTEM_NAME} STREQUAL "Linux" AND NOT TORCH_CXXFLAGS)
+    message(WARNING
+      "When building on Linux TORCH_CXXFLAGS are almost always required but were not detected. "
+      "It is very likely this this will produce a non-functional installation. "
+      "See notes in build_tools/cmake/TorchMLIRPyTorch.cmake.")
+  endif()
   message(STATUS "TORCH_LIBRARIES = ${TORCH_LIBRARIES}")
 endif()
 
diff --git a/projects/pt1/python/CMakeLists.txt b/projects/pt1/python/CMakeLists.txt
index 23dd5be4071c..e951772df935 100644
--- a/projects/pt1/python/CMakeLists.txt
+++ b/projects/pt1/python/CMakeLists.txt
@@ -15,8 +15,6 @@ add_compile_definitions("MLIR_PYTHON_PACKAGE_PREFIX=torch_mlir.")
 # PyTorch
 ################################################################################
 
-option(TORCH_MLIR_USE_INSTALLED_PYTORCH "Build from local PyTorch in environment" ON)
-
 if (NOT TORCH_MLIR_USE_INSTALLED_PYTORCH)
   # Source builds
   set(ENV{TORCH_MLIR_SRC_PYTORCH_REPO} ${TORCH_MLIR_SRC_PYTORCH_REPO})