[PATCH] D79151: build: use `find_package(Python3)` if available (llvm runtimes).

[Vlad Vereschaka via Phabricator via llvm-commits]

vvereschaka created this revision.
vvereschaka added reviewers: compnerd, phosek.
vvereschaka added a project: LLVM.
Herald added subscribers: llvm-commits, mgorny.
vvereschaka added a comment.

Hi @compnerd,
here is one more place, which needs a proper detection for Python3/Python2.
I just copied a part of your changes accordingly.


This is primarily motivated by the desire to move from Python2 to
Python3.  `PYTHON_EXECUTABLE` is ambiguous.  This explicitly identifies
the python interpreter in use.  Since the LLVM build seems to be able to
completed successfully with python3, use that across the build.  The old
path aliases `PYTHON_EXECUTABLE` to be treated as Python3.

Based on commit cd84bfb8142bc7ff3a07a188ffb809f1d86d1fd7 <https://reviews.llvm.org/rGcd84bfb8142bc7ff3a07a188ffb809f1d86d1fd7>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D79151

Files:
  llvm/runtimes/CMakeLists.txt


Index: llvm/runtimes/CMakeLists.txt
===================================================================
--- llvm/runtimes/CMakeLists.txt
+++ llvm/runtimes/CMakeLists.txt
@@ -112,7 +112,40 @@
   # Handle common options used by all runtimes.
   include(AddLLVM)
   include(HandleLLVMOptions)
-  include(FindPythonInterp)
+
+  if(CMAKE_VERSION VERSION_LESS 3.12)
+    include(FindPythonInterp)
+    if( NOT PYTHONINTERP_FOUND )
+      message(FATAL_ERROR
+    "Unable to find Python interpreter, required for builds and testing.
+
+    Please install Python or specify the PYTHON_EXECUTABLE CMake variable.")
+    endif()
+
+    if( ${PYTHON_VERSION_STRING} VERSION_LESS 2.7 )
+      message(FATAL_ERROR "Python 2.7 or newer is required")
+    endif()
+
+    add_executable(Python3::Interpreter IMPORTED)
+    set_target_properties(Python3::Interpreter PROPERTIES
+      IMPORTED_LOCATION ${PYTHON_EXECUTABLE})
+    set(Python3_EXECUTABLE ${PYTHON_EXECUTABLE})
+  else()
+    find_package(Python3 COMPONENTS Interpreter)
+    if(NOT Python3_Interpreter_FOUND)
+      message(WARNING "Python3 not found, using python2 as a fallback")
+      find_package(Python2 COMPONENTS Interpreter REQUIRED)
+      if(Python2_VERSION VERSION_LESS 2.7)
+        message(SEND_ERROR "Python 2.7 or newer is required")
+      endif()
+
+      # Treat python2 as python3
+      add_executable(Python3::Interpreter IMPORTED)
+      set_target_properties(Python3::Interpreter PROPERTIES
+        IMPORTED_LOCATION ${Python2_EXECUTABLE})
+      set(Python3_EXECUTABLE ${Python2_EXECUTABLE})
+    endif()
+  endif()
 
   # Remove the -nostdlib++ option we've added earlier.
   string(REPLACE "-nostdlib++" "" CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS}")


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